[RFC PATCH 0/3] drivers: mfd: Versatile Express SPC support

[RFC PATCH 0/3] drivers: mfd: Versatile Express SPC support

[Lorenzo Pieralisi]

This patch series introduces support for the Versatile Express Serial
Power Controller (SPC) present in ARM Versatile Express TC2 core tiles.
SPC driver is a fundamental component of TC2 power management and allows
to carry out C-state management and DVFS for A15 and A7 clusters.

First two patches provide changes required by SPC to comply with the
Versatile Express config API, third patch is the SPC driver implementation.

Code extensively exercised through CPUidle and CPUfreq power states and
operating point transitions.

Lorenzo Pieralisi (2):
  drivers: mfd: vexpress: add timeout API to vexpress config interface
  drivers: mfd: vexpress: add Serial Power Controller (SPC) support

Pawel Moll (1):
  drivers: mfd: refactor the vexpress config bridge API

 Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  35 +
 drivers/mfd/Kconfig                                    |   7 +
 drivers/mfd/Makefile                                   |   1 +
 drivers/mfd/vexpress-config.c                          |  87 +-
 drivers/mfd/vexpress-spc.c                             | 626 ++++++++++
 drivers/mfd/vexpress-sysreg.c                          |   2 +-
 include/linux/vexpress.h                               |  82 +-
 7 files changed, 800 insertions(+), 40 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mfd/vexpress-spc.txt
 create mode 100644 drivers/mfd/vexpress-spc.c

-- 
1.8.2.2

[RFC PATCH 0/3] drivers: mfd: Versatile Express SPC support

[Lorenzo Pieralisi]

This patch series introduces support for the Versatile Express Serial
Power Controller (SPC) present in ARM Versatile Express TC2 core tiles.
SPC driver is a fundamental component of TC2 power management and allows
to carry out C-state management and DVFS for A15 and A7 clusters.

First two patches provide changes required by SPC to comply with the
Versatile Express config API, third patch is the SPC driver implementation.

Code extensively exercised through CPUidle and CPUfreq power states and
operating point transitions.

Lorenzo Pieralisi (2):
  drivers: mfd: vexpress: add timeout API to vexpress config interface
  drivers: mfd: vexpress: add Serial Power Controller (SPC) support

Pawel Moll (1):
  drivers: mfd: refactor the vexpress config bridge API

 Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  35 +
 drivers/mfd/Kconfig                                    |   7 +
 drivers/mfd/Makefile                                   |   1 +
 drivers/mfd/vexpress-config.c                          |  87 +-
 drivers/mfd/vexpress-spc.c                             | 626 ++++++++++
 drivers/mfd/vexpress-sysreg.c                          |   2 +-
 include/linux/vexpress.h                               |  82 +-
 7 files changed, 800 insertions(+), 40 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mfd/vexpress-spc.txt
 create mode 100644 drivers/mfd/vexpress-spc.c

-- 
1.8.2.2

[RFC PATCH 0/3] drivers: mfd: Versatile Express SPC support

[Lorenzo Pieralisi]

This patch series introduces support for the Versatile Express Serial
Power Controller (SPC) present in ARM Versatile Express TC2 core tiles.
SPC driver is a fundamental component of TC2 power management and allows
to carry out C-state management and DVFS for A15 and A7 clusters.

First two patches provide changes required by SPC to comply with the
Versatile Express config API, third patch is the SPC driver implementation.

Code extensively exercised through CPUidle and CPUfreq power states and
operating point transitions.

Lorenzo Pieralisi (2):
  drivers: mfd: vexpress: add timeout API to vexpress config interface
  drivers: mfd: vexpress: add Serial Power Controller (SPC) support

Pawel Moll (1):
  drivers: mfd: refactor the vexpress config bridge API

 Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  35 +
 drivers/mfd/Kconfig                                    |   7 +
 drivers/mfd/Makefile                                   |   1 +
 drivers/mfd/vexpress-config.c                          |  87 +-
 drivers/mfd/vexpress-spc.c                             | 626 ++++++++++
 drivers/mfd/vexpress-sysreg.c                          |   2 +-
 include/linux/vexpress.h                               |  82 +-
 7 files changed, 800 insertions(+), 40 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mfd/vexpress-spc.txt
 create mode 100644 drivers/mfd/vexpress-spc.c

-- 
1.8.2.2

[RFC PATCH 1/3] drivers: mfd: refactor the vexpress config bridge API

[Lorenzo Pieralisi]

From: Pawel Moll <pawel.moll@arm.com>

The introduction of Serial Power Controller (SPC) requires the vexpress
config interface to change slightly since the SPC memory mapped interface
can be used as configuration bus but also for operating points
programming and retrieval. The helper that allocates the bridge functions
requires an additional parameter allowing to request component specific
functions that need not be initialized through device tree bindings but
just using simple look-up and statically defined constants.

This patch introduces the necessary changes to the vexpress config layer
to cater for the new vexpress bridge interface requirements.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
---
 drivers/mfd/vexpress-config.c | 61 ++++++----
 drivers/mfd/vexpress-sysreg.c |  2 +-
 include/linux/vexpress.h      | 16 ++-
 3 files changed, 51 insertions(+), 28 deletions(-)

diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
index 84ce6b9..1af2b0e 100644
--- a/drivers/mfd/vexpress-config.c
+++ b/drivers/mfd/vexpress-config.c
@@ -86,29 +86,13 @@ void vexpress_config_bridge_unregister(struct vexpress_config_bridge *bridge)
 }
 EXPORT_SYMBOL(vexpress_config_bridge_unregister);
 
-
-struct vexpress_config_func {
-	struct vexpress_config_bridge *bridge;
-	void *func;
-};
-
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node)
+static struct vexpress_config_bridge *
+		vexpress_config_bridge_find(struct device_node *node)
 {
-	struct device_node *bridge_node;
-	struct vexpress_config_func *func;
 	int i;
+	struct vexpress_config_bridge *res = NULL;
+	struct device_node *bridge_node = of_node_get(node);
 
-	if (WARN_ON(dev && node && dev->of_node != node))
-		return NULL;
-	if (dev && !node)
-		node = dev->of_node;
-
-	func = kzalloc(sizeof(*func), GFP_KERNEL);
-	if (!func)
-		return NULL;
-
-	bridge_node = of_node_get(node);
 	while (bridge_node) {
 		const __be32 *prop = of_get_property(bridge_node,
 				"arm,vexpress,config-bridge", NULL);
@@ -129,13 +113,46 @@ struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
 
 		if (test_bit(i, vexpress_config_bridges_map) &&
 				bridge->node == bridge_node) {
-			func->bridge = bridge;
-			func->func = bridge->info->func_get(dev, node);
+			res = bridge;
 			break;
 		}
 	}
 	mutex_unlock(&vexpress_config_bridges_mutex);
 
+	return res;
+}
+
+
+struct vexpress_config_func {
+	struct vexpress_config_bridge *bridge;
+	void *func;
+};
+
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id)
+{
+	struct vexpress_config_func *func;
+
+	if (WARN_ON(dev && node && dev->of_node != node))
+		return NULL;
+	if (dev && !node)
+		node = dev->of_node;
+
+	if (!bridge)
+		bridge = vexpress_config_bridge_find(node);
+	if (!bridge)
+		return NULL;
+
+	func = kzalloc(sizeof(*func), GFP_KERNEL);
+	if (!func)
+		return NULL;
+
+	func->bridge = bridge;
+	func->func = bridge->info->func_get(dev, node, id);
+
 	if (!func->func) {
 		of_node_put(node);
 		kfree(func);
diff --git a/drivers/mfd/vexpress-sysreg.c b/drivers/mfd/vexpress-sysreg.c
index 96a020b..d2599aa 100644
--- a/drivers/mfd/vexpress-sysreg.c
+++ b/drivers/mfd/vexpress-sysreg.c
@@ -165,7 +165,7 @@ static u32 *vexpress_sysreg_config_data;
 static int vexpress_sysreg_config_tries;
 
 static void *vexpress_sysreg_config_func_get(struct device *dev,
-		struct device_node *node)
+		struct device_node *node, const char *id)
 {
 	struct vexpress_sysreg_config_func *config_func;
 	u32 site;
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index 6e7980d..50368e0 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -68,7 +68,8 @@
  */
 struct vexpress_config_bridge_info {
 	const char *name;
-	void *(*func_get)(struct device *dev, struct device_node *node);
+	void *(*func_get)(struct device *dev, struct device_node *node,
+			  const char *id);
 	void (*func_put)(void *func);
 	int (*func_exec)(void *func, int offset, bool write, u32 *data);
 };
@@ -87,12 +88,17 @@ void vexpress_config_complete(struct vexpress_config_bridge *bridge,
 
 struct vexpress_config_func;
 
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node);
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id);
+#define vexpress_config_func_get(bridge, id) \
+		__vexpress_config_func_get(bridge, NULL, NULL, id)
 #define vexpress_config_func_get_by_dev(dev) \
-		__vexpress_config_func_get(dev, NULL)
+		__vexpress_config_func_get(NULL, dev, NULL, NULL)
 #define vexpress_config_func_get_by_node(node) \
-		__vexpress_config_func_get(NULL, node)
+		__vexpress_config_func_get(NULL, NULL, node, NULL)
 void vexpress_config_func_put(struct vexpress_config_func *func);
 
 /* Both may sleep! */
-- 
1.8.2.2

[RFC PATCH 1/3] drivers: mfd: refactor the vexpress config bridge API

[Lorenzo Pieralisi]

From: Pawel Moll <pawel.moll@arm.com>

The introduction of Serial Power Controller (SPC) requires the vexpress
config interface to change slightly since the SPC memory mapped interface
can be used as configuration bus but also for operating points
programming and retrieval. The helper that allocates the bridge functions
requires an additional parameter allowing to request component specific
functions that need not be initialized through device tree bindings but
just using simple look-up and statically defined constants.

This patch introduces the necessary changes to the vexpress config layer
to cater for the new vexpress bridge interface requirements.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
---
 drivers/mfd/vexpress-config.c | 61 ++++++----
 drivers/mfd/vexpress-sysreg.c |  2 +-
 include/linux/vexpress.h      | 16 ++-
 3 files changed, 51 insertions(+), 28 deletions(-)

diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
index 84ce6b9..1af2b0e 100644
--- a/drivers/mfd/vexpress-config.c
+++ b/drivers/mfd/vexpress-config.c
@@ -86,29 +86,13 @@ void vexpress_config_bridge_unregister(struct vexpress_config_bridge *bridge)
 }
 EXPORT_SYMBOL(vexpress_config_bridge_unregister);
 
-
-struct vexpress_config_func {
-	struct vexpress_config_bridge *bridge;
-	void *func;
-};
-
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node)
+static struct vexpress_config_bridge *
+		vexpress_config_bridge_find(struct device_node *node)
 {
-	struct device_node *bridge_node;
-	struct vexpress_config_func *func;
 	int i;
+	struct vexpress_config_bridge *res = NULL;
+	struct device_node *bridge_node = of_node_get(node);
 
-	if (WARN_ON(dev && node && dev->of_node != node))
-		return NULL;
-	if (dev && !node)
-		node = dev->of_node;
-
-	func = kzalloc(sizeof(*func), GFP_KERNEL);
-	if (!func)
-		return NULL;
-
-	bridge_node = of_node_get(node);
 	while (bridge_node) {
 		const __be32 *prop = of_get_property(bridge_node,
 				"arm,vexpress,config-bridge", NULL);
@@ -129,13 +113,46 @@ struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
 
 		if (test_bit(i, vexpress_config_bridges_map) &&
 				bridge->node == bridge_node) {
-			func->bridge = bridge;
-			func->func = bridge->info->func_get(dev, node);
+			res = bridge;
 			break;
 		}
 	}
 	mutex_unlock(&vexpress_config_bridges_mutex);
 
+	return res;
+}
+
+
+struct vexpress_config_func {
+	struct vexpress_config_bridge *bridge;
+	void *func;
+};
+
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id)
+{
+	struct vexpress_config_func *func;
+
+	if (WARN_ON(dev && node && dev->of_node != node))
+		return NULL;
+	if (dev && !node)
+		node = dev->of_node;
+
+	if (!bridge)
+		bridge = vexpress_config_bridge_find(node);
+	if (!bridge)
+		return NULL;
+
+	func = kzalloc(sizeof(*func), GFP_KERNEL);
+	if (!func)
+		return NULL;
+
+	func->bridge = bridge;
+	func->func = bridge->info->func_get(dev, node, id);
+
 	if (!func->func) {
 		of_node_put(node);
 		kfree(func);
diff --git a/drivers/mfd/vexpress-sysreg.c b/drivers/mfd/vexpress-sysreg.c
index 96a020b..d2599aa 100644
--- a/drivers/mfd/vexpress-sysreg.c
+++ b/drivers/mfd/vexpress-sysreg.c
@@ -165,7 +165,7 @@ static u32 *vexpress_sysreg_config_data;
 static int vexpress_sysreg_config_tries;
 
 static void *vexpress_sysreg_config_func_get(struct device *dev,
-		struct device_node *node)
+		struct device_node *node, const char *id)
 {
 	struct vexpress_sysreg_config_func *config_func;
 	u32 site;
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index 6e7980d..50368e0 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -68,7 +68,8 @@
  */
 struct vexpress_config_bridge_info {
 	const char *name;
-	void *(*func_get)(struct device *dev, struct device_node *node);
+	void *(*func_get)(struct device *dev, struct device_node *node,
+			  const char *id);
 	void (*func_put)(void *func);
 	int (*func_exec)(void *func, int offset, bool write, u32 *data);
 };
@@ -87,12 +88,17 @@ void vexpress_config_complete(struct vexpress_config_bridge *bridge,
 
 struct vexpress_config_func;
 
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node);
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id);
+#define vexpress_config_func_get(bridge, id) \
+		__vexpress_config_func_get(bridge, NULL, NULL, id)
 #define vexpress_config_func_get_by_dev(dev) \
-		__vexpress_config_func_get(dev, NULL)
+		__vexpress_config_func_get(NULL, dev, NULL, NULL)
 #define vexpress_config_func_get_by_node(node) \
-		__vexpress_config_func_get(NULL, node)
+		__vexpress_config_func_get(NULL, NULL, node, NULL)
 void vexpress_config_func_put(struct vexpress_config_func *func);
 
 /* Both may sleep! */
-- 
1.8.2.2

[RFC PATCH 1/3] drivers: mfd: refactor the vexpress config bridge API

[Lorenzo Pieralisi]

From: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>

The introduction of Serial Power Controller (SPC) requires the vexpress
config interface to change slightly since the SPC memory mapped interface
can be used as configuration bus but also for operating points
programming and retrieval. The helper that allocates the bridge functions
requires an additional parameter allowing to request component specific
functions that need not be initialized through device tree bindings but
just using simple look-up and statically defined constants.

This patch introduces the necessary changes to the vexpress config layer
to cater for the new vexpress bridge interface requirements.

Cc: Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Achin Gupta <achin.gupta-5wv7dgnIgG8@public.gmane.org>
Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha-5wv7dgnIgG8@public.gmane.org>
Cc: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
Cc: Nicolas Pitre <nicolas.pitre-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Amit Kucheria <amit.kucheria-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Jon Medhurst <tixy-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
---
 drivers/mfd/vexpress-config.c | 61 ++++++----
 drivers/mfd/vexpress-sysreg.c |  2 +-
 include/linux/vexpress.h      | 16 ++-
 3 files changed, 51 insertions(+), 28 deletions(-)

diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
index 84ce6b9..1af2b0e 100644
--- a/drivers/mfd/vexpress-config.c
+++ b/drivers/mfd/vexpress-config.c
@@ -86,29 +86,13 @@ void vexpress_config_bridge_unregister(struct vexpress_config_bridge *bridge)
 }
 EXPORT_SYMBOL(vexpress_config_bridge_unregister);
 
-
-struct vexpress_config_func {
-	struct vexpress_config_bridge *bridge;
-	void *func;
-};
-
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node)
+static struct vexpress_config_bridge *
+		vexpress_config_bridge_find(struct device_node *node)
 {
-	struct device_node *bridge_node;
-	struct vexpress_config_func *func;
 	int i;
+	struct vexpress_config_bridge *res = NULL;
+	struct device_node *bridge_node = of_node_get(node);
 
-	if (WARN_ON(dev && node && dev->of_node != node))
-		return NULL;
-	if (dev && !node)
-		node = dev->of_node;
-
-	func = kzalloc(sizeof(*func), GFP_KERNEL);
-	if (!func)
-		return NULL;
-
-	bridge_node = of_node_get(node);
 	while (bridge_node) {
 		const __be32 *prop = of_get_property(bridge_node,
 				"arm,vexpress,config-bridge", NULL);
@@ -129,13 +113,46 @@ struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
 
 		if (test_bit(i, vexpress_config_bridges_map) &&
 				bridge->node == bridge_node) {
-			func->bridge = bridge;
-			func->func = bridge->info->func_get(dev, node);
+			res = bridge;
 			break;
 		}
 	}
 	mutex_unlock(&vexpress_config_bridges_mutex);
 
+	return res;
+}
+
+
+struct vexpress_config_func {
+	struct vexpress_config_bridge *bridge;
+	void *func;
+};
+
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id)
+{
+	struct vexpress_config_func *func;
+
+	if (WARN_ON(dev && node && dev->of_node != node))
+		return NULL;
+	if (dev && !node)
+		node = dev->of_node;
+
+	if (!bridge)
+		bridge = vexpress_config_bridge_find(node);
+	if (!bridge)
+		return NULL;
+
+	func = kzalloc(sizeof(*func), GFP_KERNEL);
+	if (!func)
+		return NULL;
+
+	func->bridge = bridge;
+	func->func = bridge->info->func_get(dev, node, id);
+
 	if (!func->func) {
 		of_node_put(node);
 		kfree(func);
diff --git a/drivers/mfd/vexpress-sysreg.c b/drivers/mfd/vexpress-sysreg.c
index 96a020b..d2599aa 100644
--- a/drivers/mfd/vexpress-sysreg.c
+++ b/drivers/mfd/vexpress-sysreg.c
@@ -165,7 +165,7 @@ static u32 *vexpress_sysreg_config_data;
 static int vexpress_sysreg_config_tries;
 
 static void *vexpress_sysreg_config_func_get(struct device *dev,
-		struct device_node *node)
+		struct device_node *node, const char *id)
 {
 	struct vexpress_sysreg_config_func *config_func;
 	u32 site;
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index 6e7980d..50368e0 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -68,7 +68,8 @@
  */
 struct vexpress_config_bridge_info {
 	const char *name;
-	void *(*func_get)(struct device *dev, struct device_node *node);
+	void *(*func_get)(struct device *dev, struct device_node *node,
+			  const char *id);
 	void (*func_put)(void *func);
 	int (*func_exec)(void *func, int offset, bool write, u32 *data);
 };
@@ -87,12 +88,17 @@ void vexpress_config_complete(struct vexpress_config_bridge *bridge,
 
 struct vexpress_config_func;
 
-struct vexpress_config_func *__vexpress_config_func_get(struct device *dev,
-		struct device_node *node);
+struct vexpress_config_func *__vexpress_config_func_get(
+		struct vexpress_config_bridge *bridge,
+		struct device *dev,
+		struct device_node *node,
+		const char *id);
+#define vexpress_config_func_get(bridge, id) \
+		__vexpress_config_func_get(bridge, NULL, NULL, id)
 #define vexpress_config_func_get_by_dev(dev) \
-		__vexpress_config_func_get(dev, NULL)
+		__vexpress_config_func_get(NULL, dev, NULL, NULL)
 #define vexpress_config_func_get_by_node(node) \
-		__vexpress_config_func_get(NULL, node)
+		__vexpress_config_func_get(NULL, NULL, node, NULL)
 void vexpress_config_func_put(struct vexpress_config_func *func);
 
 /* Both may sleep! */
-- 
1.8.2.2

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

In case some transactions to the Serial Power Controller (SPC) are lost owing
to multiple operations handled at once by the M3 controller the OS needs to
rely on a configuration API that can time out so that failures do not result
in an unusable system.

This patch adds a timeout API to the vexpress config programming interface,
and refactors the existing read/write functions so that they can be reused
seamlessly on top of the newly defined API.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
---
 drivers/mfd/vexpress-config.c | 26 +++++++---
 include/linux/vexpress.h      | 23 ++++++--
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
index 1af2b0e..6f4aa5a 100644
--- a/drivers/mfd/vexpress-config.c
+++ b/drivers/mfd/vexpress-config.c
@@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
 }
 EXPORT_SYMBOL(vexpress_config_wait);
 
-int vexpress_config_read(struct vexpress_config_func *func, int offset,
-		u32 *data)
+int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
+			long jiffies)
+{
+	int ret;
+	ret = wait_for_completion_timeout(&trans->completion, jiffies);
+
+	return ret ? trans->status : -ETIMEDOUT;
+}
+EXPORT_SYMBOL(vexpress_config_wait_timeout);
+
+int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
+		u32 *data, long jiffies)
 {
 	struct vexpress_config_trans trans = {
 		.func = func,
@@ -279,14 +289,14 @@ int vexpress_config_read(struct vexpress_config_func *func, int offset,
 	int status = vexpress_config_schedule(&trans);
 
 	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
-		status = vexpress_config_wait(&trans);
+		status = vexpress_config_wait_timeout(&trans, jiffies);
 
 	return status;
 }
-EXPORT_SYMBOL(vexpress_config_read);
+EXPORT_SYMBOL(vexpress_config_read_timeout);
 
-int vexpress_config_write(struct vexpress_config_func *func, int offset,
-		u32 data)
+int vexpress_config_write_timeout(struct vexpress_config_func *func,
+				  int offset, u32 data, long jiffies)
 {
 	struct vexpress_config_trans trans = {
 		.func = func,
@@ -298,8 +308,8 @@ int vexpress_config_write(struct vexpress_config_func *func, int offset,
 	int status = vexpress_config_schedule(&trans);
 
 	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
-		status = vexpress_config_wait(&trans);
+		status = vexpress_config_wait_timeout(&trans, jiffies);
 
 	return status;
 }
-EXPORT_SYMBOL(vexpress_config_write);
+EXPORT_SYMBOL(vexpress_config_write_timeout);
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index 50368e0..e5015d8 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -15,6 +15,7 @@
 #define _LINUX_VEXPRESS_H
 
 #include <linux/device.h>
+#include <linux/sched.h>
 
 #define VEXPRESS_SITE_MB		0
 #define VEXPRESS_SITE_DB1		1
@@ -102,10 +103,24 @@ struct vexpress_config_func *__vexpress_config_func_get(
 void vexpress_config_func_put(struct vexpress_config_func *func);
 
 /* Both may sleep! */
-int vexpress_config_read(struct vexpress_config_func *func, int offset,
-		u32 *data);
-int vexpress_config_write(struct vexpress_config_func *func, int offset,
-		u32 data);
+int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
+		u32 *data, long jiffies);
+int vexpress_config_write_timeout(struct vexpress_config_func *func,
+		int offset, u32 data, long jiffies);
+
+static inline int vexpress_config_read(struct vexpress_config_func *func,
+				 int offset, u32 *data)
+{
+	return vexpress_config_read_timeout(func, offset, data,
+					     MAX_SCHEDULE_TIMEOUT);
+}
+
+static inline int vexpress_config_write(struct vexpress_config_func *func,
+				 int offset, u32 data)
+{
+	return vexpress_config_write_timeout(func, offset, data,
+					     MAX_SCHEDULE_TIMEOUT);
+}
 
 /* Platform control */
 
-- 
1.8.2.2

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

In case some transactions to the Serial Power Controller (SPC) are lost owing
to multiple operations handled at once by the M3 controller the OS needs to
rely on a configuration API that can time out so that failures do not result
in an unusable system.

This patch adds a timeout API to the vexpress config programming interface,
and refactors the existing read/write functions so that they can be reused
seamlessly on top of the newly defined API.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
---
 drivers/mfd/vexpress-config.c | 26 +++++++---
 include/linux/vexpress.h      | 23 ++++++--
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
index 1af2b0e..6f4aa5a 100644
--- a/drivers/mfd/vexpress-config.c
+++ b/drivers/mfd/vexpress-config.c
@@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
 }
 EXPORT_SYMBOL(vexpress_config_wait);
 
-int vexpress_config_read(struct vexpress_config_func *func, int offset,
-		u32 *data)
+int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
+			long jiffies)
+{
+	int ret;
+	ret = wait_for_completion_timeout(&trans->completion, jiffies);
+
+	return ret ? trans->status : -ETIMEDOUT;
+}
+EXPORT_SYMBOL(vexpress_config_wait_timeout);
+
+int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
+		u32 *data, long jiffies)
 {
 	struct vexpress_config_trans trans = {
 		.func = func,
@@ -279,14 +289,14 @@ int vexpress_config_read(struct vexpress_config_func *func, int offset,
 	int status = vexpress_config_schedule(&trans);
 
 	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
-		status = vexpress_config_wait(&trans);
+		status = vexpress_config_wait_timeout(&trans, jiffies);
 
 	return status;
 }
-EXPORT_SYMBOL(vexpress_config_read);
+EXPORT_SYMBOL(vexpress_config_read_timeout);
 
-int vexpress_config_write(struct vexpress_config_func *func, int offset,
-		u32 data)
+int vexpress_config_write_timeout(struct vexpress_config_func *func,
+				  int offset, u32 data, long jiffies)
 {
 	struct vexpress_config_trans trans = {
 		.func = func,
@@ -298,8 +308,8 @@ int vexpress_config_write(struct vexpress_config_func *func, int offset,
 	int status = vexpress_config_schedule(&trans);
 
 	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
-		status = vexpress_config_wait(&trans);
+		status = vexpress_config_wait_timeout(&trans, jiffies);
 
 	return status;
 }
-EXPORT_SYMBOL(vexpress_config_write);
+EXPORT_SYMBOL(vexpress_config_write_timeout);
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index 50368e0..e5015d8 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -15,6 +15,7 @@
 #define _LINUX_VEXPRESS_H
 
 #include <linux/device.h>
+#include <linux/sched.h>
 
 #define VEXPRESS_SITE_MB		0
 #define VEXPRESS_SITE_DB1		1
@@ -102,10 +103,24 @@ struct vexpress_config_func *__vexpress_config_func_get(
 void vexpress_config_func_put(struct vexpress_config_func *func);
 
 /* Both may sleep! */
-int vexpress_config_read(struct vexpress_config_func *func, int offset,
-		u32 *data);
-int vexpress_config_write(struct vexpress_config_func *func, int offset,
-		u32 data);
+int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
+		u32 *data, long jiffies);
+int vexpress_config_write_timeout(struct vexpress_config_func *func,
+		int offset, u32 data, long jiffies);
+
+static inline int vexpress_config_read(struct vexpress_config_func *func,
+				 int offset, u32 *data)
+{
+	return vexpress_config_read_timeout(func, offset, data,
+					     MAX_SCHEDULE_TIMEOUT);
+}
+
+static inline int vexpress_config_write(struct vexpress_config_func *func,
+				 int offset, u32 data)
+{
+	return vexpress_config_write_timeout(func, offset, data,
+					     MAX_SCHEDULE_TIMEOUT);
+}
 
 /* Platform control */
 
-- 
1.8.2.2

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> In case some transactions to the Serial Power Controller (SPC) are lost owing
> to multiple operations handled at once by the M3 controller the OS needs to
> rely on a configuration API that can time out so that failures do not result
> in an unusable system.
> 
> This patch adds a timeout API to the vexpress config programming interface,
> and refactors the existing read/write functions so that they can be reused
> seamlessly on top of the newly defined API.

Isn't one of the main purposes of the config interface to serialise
transactions to the config bus, so why would the SPC be handling
multiple transactions at once? And if we can in fact loose transactions
doesn't this mean we get random failures in the system? E.g. if this
happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

Also, I think the code implementing timeouts is broken, see below.

> Cc: Samuel Ortiz <sameo@linux.intel.com>
> Cc: Achin Gupta <achin.gupta@arm.com>
> Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> Cc: Amit Kucheria <amit.kucheria@linaro.org>
> Cc: Jon Medhurst <tixy@linaro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> ---
>  drivers/mfd/vexpress-config.c | 26 +++++++---
>  include/linux/vexpress.h      | 23 ++++++--
>  2 files changed, 37 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> index 1af2b0e..6f4aa5a 100644
> --- a/drivers/mfd/vexpress-config.c
> +++ b/drivers/mfd/vexpress-config.c
> @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
>  }
>  EXPORT_SYMBOL(vexpress_config_wait);
>  
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data)
> +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> +			long jiffies)
> +{
> +	int ret;
> +	ret = wait_for_completion_timeout(&trans->completion, jiffies);

If the request times out, don't we need to call vexpress_config_complete
to dequeue the timed out request and trigger the next one? Though we
will still have a problem where the timeout happens but the request
then does in fact complete normally, in that case we would signal
completion of the second request before it has in fact completed.

So, if transactions really can get silently dropped by thing on the end
of the config bus, then we must have a mechanism for associating a
particular transaction with a completion signal, otherwise we won't know
what transaction actually got completed OK and which ones were dropped
and should receive -ETIMEDOUT.

Finally, I don't think these issues are purely theoretical, I'm pretty
certain that the kernel panics and spinlock bad magic errors I see with
his patch series are due to requests completing after they have been
timed out and then the stack based transaction object is being accessed
after it has gone out of scope.

> +	return ret ? trans->status : -ETIMEDOUT;
> +}
> +EXPORT_SYMBOL(vexpress_config_wait_timeout);
> +
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -279,14 +289,14 @@ int vexpress_config_read(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_read);
> +EXPORT_SYMBOL(vexpress_config_read_timeout);
>  
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data)
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +				  int offset, u32 data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -298,8 +308,8 @@ int vexpress_config_write(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_write);
> +EXPORT_SYMBOL(vexpress_config_write_timeout);
> diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
> index 50368e0..e5015d8 100644
> --- a/include/linux/vexpress.h
> +++ b/include/linux/vexpress.h
> @@ -15,6 +15,7 @@
>  #define _LINUX_VEXPRESS_H
>  
>  #include <linux/device.h>
> +#include <linux/sched.h>
>  
>  #define VEXPRESS_SITE_MB		0
>  #define VEXPRESS_SITE_DB1		1
> @@ -102,10 +103,24 @@ struct vexpress_config_func *__vexpress_config_func_get(
>  void vexpress_config_func_put(struct vexpress_config_func *func);
>  
>  /* Both may sleep! */
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data);
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data);
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies);
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +		int offset, u32 data, long jiffies);
> +
> +static inline int vexpress_config_read(struct vexpress_config_func *func,
> +				 int offset, u32 *data)
> +{
> +	return vexpress_config_read_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
> +
> +static inline int vexpress_config_write(struct vexpress_config_func *func,
> +				 int offset, u32 data)
> +{
> +	return vexpress_config_write_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
>  
>  /* Platform control */
>  

-- 
Tixy

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> In case some transactions to the Serial Power Controller (SPC) are lost owing
> to multiple operations handled at once by the M3 controller the OS needs to
> rely on a configuration API that can time out so that failures do not result
> in an unusable system.
> 
> This patch adds a timeout API to the vexpress config programming interface,
> and refactors the existing read/write functions so that they can be reused
> seamlessly on top of the newly defined API.

Isn't one of the main purposes of the config interface to serialise
transactions to the config bus, so why would the SPC be handling
multiple transactions at once? And if we can in fact loose transactions
doesn't this mean we get random failures in the system? E.g. if this
happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

Also, I think the code implementing timeouts is broken, see below.

> Cc: Samuel Ortiz <sameo@linux.intel.com>
> Cc: Achin Gupta <achin.gupta@arm.com>
> Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> Cc: Amit Kucheria <amit.kucheria@linaro.org>
> Cc: Jon Medhurst <tixy@linaro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> ---
>  drivers/mfd/vexpress-config.c | 26 +++++++---
>  include/linux/vexpress.h      | 23 ++++++--
>  2 files changed, 37 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> index 1af2b0e..6f4aa5a 100644
> --- a/drivers/mfd/vexpress-config.c
> +++ b/drivers/mfd/vexpress-config.c
> @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
>  }
>  EXPORT_SYMBOL(vexpress_config_wait);
>  
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data)
> +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> +			long jiffies)
> +{
> +	int ret;
> +	ret = wait_for_completion_timeout(&trans->completion, jiffies);

If the request times out, don't we need to call vexpress_config_complete
to dequeue the timed out request and trigger the next one? Though we
will still have a problem where the timeout happens but the request
then does in fact complete normally, in that case we would signal
completion of the second request before it has in fact completed.

So, if transactions really can get silently dropped by thing on the end
of the config bus, then we must have a mechanism for associating a
particular transaction with a completion signal, otherwise we won't know
what transaction actually got completed OK and which ones were dropped
and should receive -ETIMEDOUT.

Finally, I don't think these issues are purely theoretical, I'm pretty
certain that the kernel panics and spinlock bad magic errors I see with
his patch series are due to requests completing after they have been
timed out and then the stack based transaction object is being accessed
after it has gone out of scope.

> +	return ret ? trans->status : -ETIMEDOUT;
> +}
> +EXPORT_SYMBOL(vexpress_config_wait_timeout);
> +
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -279,14 +289,14 @@ int vexpress_config_read(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_read);
> +EXPORT_SYMBOL(vexpress_config_read_timeout);
>  
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data)
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +				  int offset, u32 data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -298,8 +308,8 @@ int vexpress_config_write(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_write);
> +EXPORT_SYMBOL(vexpress_config_write_timeout);
> diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
> index 50368e0..e5015d8 100644
> --- a/include/linux/vexpress.h
> +++ b/include/linux/vexpress.h
> @@ -15,6 +15,7 @@
>  #define _LINUX_VEXPRESS_H
>  
>  #include <linux/device.h>
> +#include <linux/sched.h>
>  
>  #define VEXPRESS_SITE_MB		0
>  #define VEXPRESS_SITE_DB1		1
> @@ -102,10 +103,24 @@ struct vexpress_config_func *__vexpress_config_func_get(
>  void vexpress_config_func_put(struct vexpress_config_func *func);
>  
>  /* Both may sleep! */
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data);
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data);
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies);
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +		int offset, u32 data, long jiffies);
> +
> +static inline int vexpress_config_read(struct vexpress_config_func *func,
> +				 int offset, u32 *data)
> +{
> +	return vexpress_config_read_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
> +
> +static inline int vexpress_config_write(struct vexpress_config_func *func,
> +				 int offset, u32 data)
> +{
> +	return vexpress_config_write_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
>  
>  /* Platform control */
>  

-- 
Tixy

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> In case some transactions to the Serial Power Controller (SPC) are lost owing
> to multiple operations handled at once by the M3 controller the OS needs to
> rely on a configuration API that can time out so that failures do not result
> in an unusable system.
> 
> This patch adds a timeout API to the vexpress config programming interface,
> and refactors the existing read/write functions so that they can be reused
> seamlessly on top of the newly defined API.

Isn't one of the main purposes of the config interface to serialise
transactions to the config bus, so why would the SPC be handling
multiple transactions at once? And if we can in fact loose transactions
doesn't this mean we get random failures in the system? E.g. if this
happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

Also, I think the code implementing timeouts is broken, see below.

> Cc: Samuel Ortiz <sameo@linux.intel.com>
> Cc: Achin Gupta <achin.gupta@arm.com>
> Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> Cc: Amit Kucheria <amit.kucheria@linaro.org>
> Cc: Jon Medhurst <tixy@linaro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> ---
>  drivers/mfd/vexpress-config.c | 26 +++++++---
>  include/linux/vexpress.h      | 23 ++++++--
>  2 files changed, 37 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> index 1af2b0e..6f4aa5a 100644
> --- a/drivers/mfd/vexpress-config.c
> +++ b/drivers/mfd/vexpress-config.c
> @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
>  }
>  EXPORT_SYMBOL(vexpress_config_wait);
>  
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data)
> +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> +			long jiffies)
> +{
> +	int ret;
> +	ret = wait_for_completion_timeout(&trans->completion, jiffies);

If the request times out, don't we need to call vexpress_config_complete
to dequeue the timed out request and trigger the next one? Though we
will still have a problem where the timeout happens but the request
then does in fact complete normally, in that case we would signal
completion of the second request before it has in fact completed.

So, if transactions really can get silently dropped by thing on the end
of the config bus, then we must have a mechanism for associating a
particular transaction with a completion signal, otherwise we won't know
what transaction actually got completed OK and which ones were dropped
and should receive -ETIMEDOUT.

Finally, I don't think these issues are purely theoretical, I'm pretty
certain that the kernel panics and spinlock bad magic errors I see with
his patch series are due to requests completing after they have been
timed out and then the stack based transaction object is being accessed
after it has gone out of scope.

> +	return ret ? trans->status : -ETIMEDOUT;
> +}
> +EXPORT_SYMBOL(vexpress_config_wait_timeout);
> +
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -279,14 +289,14 @@ int vexpress_config_read(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_read);
> +EXPORT_SYMBOL(vexpress_config_read_timeout);
>  
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data)
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +				  int offset, u32 data, long jiffies)
>  {
>  	struct vexpress_config_trans trans = {
>  		.func = func,
> @@ -298,8 +308,8 @@ int vexpress_config_write(struct vexpress_config_func *func, int offset,
>  	int status = vexpress_config_schedule(&trans);
>  
>  	if (status == VEXPRESS_CONFIG_STATUS_WAIT)
> -		status = vexpress_config_wait(&trans);
> +		status = vexpress_config_wait_timeout(&trans, jiffies);
>  
>  	return status;
>  }
> -EXPORT_SYMBOL(vexpress_config_write);
> +EXPORT_SYMBOL(vexpress_config_write_timeout);
> diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
> index 50368e0..e5015d8 100644
> --- a/include/linux/vexpress.h
> +++ b/include/linux/vexpress.h
> @@ -15,6 +15,7 @@
>  #define _LINUX_VEXPRESS_H
>  
>  #include <linux/device.h>
> +#include <linux/sched.h>
>  
>  #define VEXPRESS_SITE_MB		0
>  #define VEXPRESS_SITE_DB1		1
> @@ -102,10 +103,24 @@ struct vexpress_config_func *__vexpress_config_func_get(
>  void vexpress_config_func_put(struct vexpress_config_func *func);
>  
>  /* Both may sleep! */
> -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> -		u32 *data);
> -int vexpress_config_write(struct vexpress_config_func *func, int offset,
> -		u32 data);
> +int vexpress_config_read_timeout(struct vexpress_config_func *func, int offset,
> +		u32 *data, long jiffies);
> +int vexpress_config_write_timeout(struct vexpress_config_func *func,
> +		int offset, u32 data, long jiffies);
> +
> +static inline int vexpress_config_read(struct vexpress_config_func *func,
> +				 int offset, u32 *data)
> +{
> +	return vexpress_config_read_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
> +
> +static inline int vexpress_config_write(struct vexpress_config_func *func,
> +				 int offset, u32 data)
> +{
> +	return vexpress_config_write_timeout(func, offset, data,
> +					     MAX_SCHEDULE_TIMEOUT);
> +}
>  
>  /* Platform control */
>  

-- 
Tixy

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > to multiple operations handled at once by the M3 controller the OS needs to
> > rely on a configuration API that can time out so that failures do not result
> > in an unusable system.
> > 
> > This patch adds a timeout API to the vexpress config programming interface,
> > and refactors the existing read/write functions so that they can be reused
> > seamlessly on top of the newly defined API.
> 
> Isn't one of the main purposes of the config interface to serialise
> transactions to the config bus, so why would the SPC be handling
> multiple transactions at once? And if we can in fact loose transactions
> doesn't this mean we get random failures in the system? E.g. if this
> happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

It has more to do with firmware carrying out background operations like
powering up a cluster when a DVFS is requested. You are absolutely right
though:

a) the timeout interface is broken, as you mentioned (I noticed after
   posting it)
b) we should not add a timeout interface to paper over FW issues

I can prepare a v2 with timeout interface dropped and extensively test that
one, I do not think we should add the required complexity that you describe
below for something that should never happen.

> Also, I think the code implementing timeouts is broken, see below.

I will have a look asap and repost a v2 accordingly.

> > Cc: Samuel Ortiz <sameo@linux.intel.com>
> > Cc: Achin Gupta <achin.gupta@arm.com>
> > Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
> > Cc: Pawel Moll <pawel.moll@arm.com>
> > Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> > Cc: Amit Kucheria <amit.kucheria@linaro.org>
> > Cc: Jon Medhurst <tixy@linaro.org>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > ---
> >  drivers/mfd/vexpress-config.c | 26 +++++++---
> >  include/linux/vexpress.h      | 23 ++++++--
> >  2 files changed, 37 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> > index 1af2b0e..6f4aa5a 100644
> > --- a/drivers/mfd/vexpress-config.c
> > +++ b/drivers/mfd/vexpress-config.c
> > @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
> >  }
> >  EXPORT_SYMBOL(vexpress_config_wait);
> >  
> > -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> > -		u32 *data)
> > +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> > +			long jiffies)
> > +{
> > +	int ret;
> > +	ret = wait_for_completion_timeout(&trans->completion, jiffies);
> 
> If the request times out, don't we need to call vexpress_config_complete
> to dequeue the timed out request and trigger the next one? Though we
> will still have a problem where the timeout happens but the request
> then does in fact complete normally, in that case we would signal
> completion of the second request before it has in fact completed.
> 
> So, if transactions really can get silently dropped by thing on the end
> of the config bus, then we must have a mechanism for associating a
> particular transaction with a completion signal, otherwise we won't know
> what transaction actually got completed OK and which ones were dropped
> and should receive -ETIMEDOUT.
> 
> Finally, I don't think these issues are purely theoretical, I'm pretty
> certain that the kernel panics and spinlock bad magic errors I see with
> his patch series are due to requests completing after they have been
> timed out and then the stack based transaction object is being accessed
> after it has gone out of scope.

You are absolutely right, apologies for wasting your time in testing it.

Thanks a lot for the review,
Lorenzo

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > to multiple operations handled at once by the M3 controller the OS needs to
> > rely on a configuration API that can time out so that failures do not result
> > in an unusable system.
> > 
> > This patch adds a timeout API to the vexpress config programming interface,
> > and refactors the existing read/write functions so that they can be reused
> > seamlessly on top of the newly defined API.
> 
> Isn't one of the main purposes of the config interface to serialise
> transactions to the config bus, so why would the SPC be handling
> multiple transactions at once? And if we can in fact loose transactions
> doesn't this mean we get random failures in the system? E.g. if this
> happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

It has more to do with firmware carrying out background operations like
powering up a cluster when a DVFS is requested. You are absolutely right
though:

a) the timeout interface is broken, as you mentioned (I noticed after
   posting it)
b) we should not add a timeout interface to paper over FW issues

I can prepare a v2 with timeout interface dropped and extensively test that
one, I do not think we should add the required complexity that you describe
below for something that should never happen.

> Also, I think the code implementing timeouts is broken, see below.

I will have a look asap and repost a v2 accordingly.

> > Cc: Samuel Ortiz <sameo@linux.intel.com>
> > Cc: Achin Gupta <achin.gupta@arm.com>
> > Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
> > Cc: Pawel Moll <pawel.moll@arm.com>
> > Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> > Cc: Amit Kucheria <amit.kucheria@linaro.org>
> > Cc: Jon Medhurst <tixy@linaro.org>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > ---
> >  drivers/mfd/vexpress-config.c | 26 +++++++---
> >  include/linux/vexpress.h      | 23 ++++++--
> >  2 files changed, 37 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> > index 1af2b0e..6f4aa5a 100644
> > --- a/drivers/mfd/vexpress-config.c
> > +++ b/drivers/mfd/vexpress-config.c
> > @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
> >  }
> >  EXPORT_SYMBOL(vexpress_config_wait);
> >  
> > -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> > -		u32 *data)
> > +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> > +			long jiffies)
> > +{
> > +	int ret;
> > +	ret = wait_for_completion_timeout(&trans->completion, jiffies);
> 
> If the request times out, don't we need to call vexpress_config_complete
> to dequeue the timed out request and trigger the next one? Though we
> will still have a problem where the timeout happens but the request
> then does in fact complete normally, in that case we would signal
> completion of the second request before it has in fact completed.
> 
> So, if transactions really can get silently dropped by thing on the end
> of the config bus, then we must have a mechanism for associating a
> particular transaction with a completion signal, otherwise we won't know
> what transaction actually got completed OK and which ones were dropped
> and should receive -ETIMEDOUT.
> 
> Finally, I don't think these issues are purely theoretical, I'm pretty
> certain that the kernel panics and spinlock bad magic errors I see with
> his patch series are due to requests completing after they have been
> timed out and then the stack based transaction object is being accessed
> after it has gone out of scope.

You are absolutely right, apologies for wasting your time in testing it.

Thanks a lot for the review,
Lorenzo

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > to multiple operations handled at once by the M3 controller the OS needs to
> > rely on a configuration API that can time out so that failures do not result
> > in an unusable system.
> > 
> > This patch adds a timeout API to the vexpress config programming interface,
> > and refactors the existing read/write functions so that they can be reused
> > seamlessly on top of the newly defined API.
> 
> Isn't one of the main purposes of the config interface to serialise
> transactions to the config bus, so why would the SPC be handling
> multiple transactions at once? And if we can in fact loose transactions
> doesn't this mean we get random failures in the system? E.g. if this
> happened at boot in vexpress_spc_populate_opps then cpufreq will fail.

It has more to do with firmware carrying out background operations like
powering up a cluster when a DVFS is requested. You are absolutely right
though:

a) the timeout interface is broken, as you mentioned (I noticed after
   posting it)
b) we should not add a timeout interface to paper over FW issues

I can prepare a v2 with timeout interface dropped and extensively test that
one, I do not think we should add the required complexity that you describe
below for something that should never happen.

> Also, I think the code implementing timeouts is broken, see below.

I will have a look asap and repost a v2 accordingly.

> > Cc: Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > Cc: Achin Gupta <achin.gupta-5wv7dgnIgG8@public.gmane.org>
> > Cc: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha-5wv7dgnIgG8@public.gmane.org>
> > Cc: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> > Cc: Nicolas Pitre <nicolas.pitre-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > Cc: Amit Kucheria <amit.kucheria-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > Cc: Jon Medhurst <tixy-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi-5wv7dgnIgG8@public.gmane.org>
> > ---
> >  drivers/mfd/vexpress-config.c | 26 +++++++---
> >  include/linux/vexpress.h      | 23 ++++++--
> >  2 files changed, 37 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/mfd/vexpress-config.c b/drivers/mfd/vexpress-config.c
> > index 1af2b0e..6f4aa5a 100644
> > --- a/drivers/mfd/vexpress-config.c
> > +++ b/drivers/mfd/vexpress-config.c
> > @@ -266,8 +266,18 @@ int vexpress_config_wait(struct vexpress_config_trans *trans)
> >  }
> >  EXPORT_SYMBOL(vexpress_config_wait);
> >  
> > -int vexpress_config_read(struct vexpress_config_func *func, int offset,
> > -		u32 *data)
> > +int vexpress_config_wait_timeout(struct vexpress_config_trans *trans,
> > +			long jiffies)
> > +{
> > +	int ret;
> > +	ret = wait_for_completion_timeout(&trans->completion, jiffies);
> 
> If the request times out, don't we need to call vexpress_config_complete
> to dequeue the timed out request and trigger the next one? Though we
> will still have a problem where the timeout happens but the request
> then does in fact complete normally, in that case we would signal
> completion of the second request before it has in fact completed.
> 
> So, if transactions really can get silently dropped by thing on the end
> of the config bus, then we must have a mechanism for associating a
> particular transaction with a completion signal, otherwise we won't know
> what transaction actually got completed OK and which ones were dropped
> and should receive -ETIMEDOUT.
> 
> Finally, I don't think these issues are purely theoretical, I'm pretty
> certain that the kernel panics and spinlock bad magic errors I see with
> his patch series are due to requests completing after they have been
> timed out and then the stack based transaction object is being accessed
> after it has gone out of scope.

You are absolutely right, apologies for wasting your time in testing it.

Thanks a lot for the review,
Lorenzo

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > to multiple operations handled at once by the M3 controller the OS needs to
> > > rely on a configuration API that can time out so that failures do not result
> > > in an unusable system.
> > > 
> > > This patch adds a timeout API to the vexpress config programming interface,
> > > and refactors the existing read/write functions so that they can be reused
> > > seamlessly on top of the newly defined API.
> > 
> > Isn't one of the main purposes of the config interface to serialise
> > transactions to the config bus, so why would the SPC be handling
> > multiple transactions at once? And if we can in fact loose transactions
> > doesn't this mean we get random failures in the system? E.g. if this
> > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> 
> It has more to do with firmware carrying out background operations like
> powering up a cluster when a DVFS is requested.

Would that make it drop transactions or just take a longer time to get
around to servicing them?


> I can prepare a v2 with timeout interface dropped and extensively test that
> one, I do not think we should add the required complexity that you describe
> below for something that should never happen.
> 
> > Also, I think the code implementing timeouts is broken, see below.
> 
> I will have a look asap and repost a v2 accordingly.

Thanks, I'll hold off any further review the current patches then.

-- 
Tixy

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > to multiple operations handled at once by the M3 controller the OS needs to
> > > rely on a configuration API that can time out so that failures do not result
> > > in an unusable system.
> > > 
> > > This patch adds a timeout API to the vexpress config programming interface,
> > > and refactors the existing read/write functions so that they can be reused
> > > seamlessly on top of the newly defined API.
> > 
> > Isn't one of the main purposes of the config interface to serialise
> > transactions to the config bus, so why would the SPC be handling
> > multiple transactions at once? And if we can in fact loose transactions
> > doesn't this mean we get random failures in the system? E.g. if this
> > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> 
> It has more to do with firmware carrying out background operations like
> powering up a cluster when a DVFS is requested.

Would that make it drop transactions or just take a longer time to get
around to servicing them?


> I can prepare a v2 with timeout interface dropped and extensively test that
> one, I do not think we should add the required complexity that you describe
> below for something that should never happen.
> 
> > Also, I think the code implementing timeouts is broken, see below.
> 
> I will have a look asap and repost a v2 accordingly.

Thanks, I'll hold off any further review the current patches then.

-- 
Tixy

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Jon Medhurst (Tixy)]

On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > to multiple operations handled at once by the M3 controller the OS needs to
> > > rely on a configuration API that can time out so that failures do not result
> > > in an unusable system.
> > > 
> > > This patch adds a timeout API to the vexpress config programming interface,
> > > and refactors the existing read/write functions so that they can be reused
> > > seamlessly on top of the newly defined API.
> > 
> > Isn't one of the main purposes of the config interface to serialise
> > transactions to the config bus, so why would the SPC be handling
> > multiple transactions at once? And if we can in fact loose transactions
> > doesn't this mean we get random failures in the system? E.g. if this
> > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> 
> It has more to do with firmware carrying out background operations like
> powering up a cluster when a DVFS is requested.

Would that make it drop transactions or just take a longer time to get
around to servicing them?


> I can prepare a v2 with timeout interface dropped and extensively test that
> one, I do not think we should add the required complexity that you describe
> below for something that should never happen.
> 
> > Also, I think the code implementing timeouts is broken, see below.
> 
> I will have a look asap and repost a v2 accordingly.

Thanks, I'll hold off any further review the current patches then.

-- 
Tixy

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 01:03:50PM +0100, Jon Medhurst (Tixy) wrote:
> On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> > On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > > to multiple operations handled at once by the M3 controller the OS needs to
> > > > rely on a configuration API that can time out so that failures do not result
> > > > in an unusable system.
> > > > 
> > > > This patch adds a timeout API to the vexpress config programming interface,
> > > > and refactors the existing read/write functions so that they can be reused
> > > > seamlessly on top of the newly defined API.
> > > 
> > > Isn't one of the main purposes of the config interface to serialise
> > > transactions to the config bus, so why would the SPC be handling
> > > multiple transactions at once? And if we can in fact loose transactions
> > > doesn't this mean we get random failures in the system? E.g. if this
> > > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> > 
> > It has more to do with firmware carrying out background operations like
> > powering up a cluster when a DVFS is requested.
> 
> Would that make it drop transactions or just take a longer time to get
> around to servicing them?

It should just take longer to service them, that's what the behaviour
should be.

Lorenzo

[RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 01:03:50PM +0100, Jon Medhurst (Tixy) wrote:
> On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> > On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > > to multiple operations handled at once by the M3 controller the OS needs to
> > > > rely on a configuration API that can time out so that failures do not result
> > > > in an unusable system.
> > > > 
> > > > This patch adds a timeout API to the vexpress config programming interface,
> > > > and refactors the existing read/write functions so that they can be reused
> > > > seamlessly on top of the newly defined API.
> > > 
> > > Isn't one of the main purposes of the config interface to serialise
> > > transactions to the config bus, so why would the SPC be handling
> > > multiple transactions at once? And if we can in fact loose transactions
> > > doesn't this mean we get random failures in the system? E.g. if this
> > > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> > 
> > It has more to do with firmware carrying out background operations like
> > powering up a cluster when a DVFS is requested.
> 
> Would that make it drop transactions or just take a longer time to get
> around to servicing them?

It should just take longer to service them, that's what the behaviour
should be.

Lorenzo

Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

[Lorenzo Pieralisi]

On Mon, Jun 03, 2013 at 01:03:50PM +0100, Jon Medhurst (Tixy) wrote:
> On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> > On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > > to multiple operations handled at once by the M3 controller the OS needs to
> > > > rely on a configuration API that can time out so that failures do not result
> > > > in an unusable system.
> > > > 
> > > > This patch adds a timeout API to the vexpress config programming interface,
> > > > and refactors the existing read/write functions so that they can be reused
> > > > seamlessly on top of the newly defined API.
> > > 
> > > Isn't one of the main purposes of the config interface to serialise
> > > transactions to the config bus, so why would the SPC be handling
> > > multiple transactions at once? And if we can in fact loose transactions
> > > doesn't this mean we get random failures in the system? E.g. if this
> > > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> > 
> > It has more to do with firmware carrying out background operations like
> > powering up a cluster when a DVFS is requested.
> 
> Would that make it drop transactions or just take a longer time to get
> around to servicing them?

It should just take longer to service them, that's what the behaviour
should be.

Lorenzo

[RFC PATCH 3/3] drivers: mfd: vexpress: add Serial Power Controller (SPC) support

[Lorenzo Pieralisi]

The TC2 versatile express core tile integrates a logic block that provides the
interface between the dual cluster test-chip and the M3 microcontroller that
carries out power management. The logic block, called Serial Power Controller
(SPC), contains several memory mapped registers to control among other things
low-power states, operating points and reset control.

This patch provides a driver that enables run-time control of features
implemented by the SPC control logic.

The driver also provides a bridge interface through the vexpress config
infrastructure. Operations allowing to read/write operating points are
made to go via the same interface as configuration transactions so that
all requests to M3 are serialized.

Device tree bindings documentation for the SPC component are provided with
the patchset.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
---
 Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  35 +
 drivers/mfd/Kconfig                                    |   7 +
 drivers/mfd/Makefile                                   |   1 +
 drivers/mfd/vexpress-spc.c                             | 626 ++++++++++
 include/linux/vexpress.h                               |  43 +
 5 files changed, 712 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/vexpress-spc.txt b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
new file mode 100644
index 0000000..1d71dc2
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
@@ -0,0 +1,35 @@
+* ARM Versatile Express Serial Power Controller device tree bindings
+
+Latest ARM development boards implement a power management interface (serial
+power controller - SPC) that is capable of managing power/voltage and
+operating point transitions, through memory mapped registers interface.
+
+On testchips like TC2 it also provides a configuration interface that can
+be used to read/write values which cannot be read/written through simple
+memory mapped reads/writes.
+
+- spc node
+
+	- compatible:
+		Usage: required
+		Value type: <stringlist>
+		Definition: must be
+			    "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc"
+	- reg:
+		Usage: required
+		Value type: <prop-encode-array>
+		Definition: A standard property that specifies the base address
+			    and the size of the SPC address space
+	- interrupts:
+		Usage: required
+		Value type: <prop-encoded-array>
+		Definition:  SPC interrupt configuration. A standard property
+			     that follows ePAPR interrupts specifications
+
+Example:
+
+spc: spc@7fff0000 {
+	compatible = "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc";
+	reg = <0 0x7FFF0000 0 0x1000>;
+	interrupts = <0 95 4>;
+};
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index d9aed15..b5259af 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1147,3 +1147,10 @@ config VEXPRESS_CONFIG
 	help
 	  Platform configuration infrastructure for the ARM Ltd.
 	  Versatile Express.
+
+config VEXPRESS_SPC
+	bool "Versatile Express SPC driver support"
+	depends on ARM
+	depends on VEXPRESS_CONFIG
+	help
+	  Serial Power Controller driver for ARM Ltd. test chips.
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 718e94a..3a01203 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -153,5 +153,6 @@ obj-$(CONFIG_MFD_SEC_CORE)	+= sec-core.o sec-irq.o
 obj-$(CONFIG_MFD_SYSCON)	+= syscon.o
 obj-$(CONFIG_MFD_LM3533)	+= lm3533-core.o lm3533-ctrlbank.o
 obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o vexpress-sysreg.o
+obj-$(CONFIG_VEXPRESS_SPC)	+= vexpress-spc.o
 obj-$(CONFIG_MFD_RETU)		+= retu-mfd.o
 obj-$(CONFIG_MFD_AS3711)	+= as3711.o
diff --git a/drivers/mfd/vexpress-spc.c b/drivers/mfd/vexpress-spc.c
new file mode 100644
index 0000000..f78257a
--- /dev/null
+++ b/drivers/mfd/vexpress-spc.c
@@ -0,0 +1,626 @@
+/*
+ * Versatile Express Serial Power Controller (SPC) support
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ *
+ * Author(s): Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+ *            Achin Gupta           <achin.gupta@arm.com>
+ *            Lorenzo Pieralisi     <lorenzo.pieralisi@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+#include <linux/vexpress.h>
+
+#include <asm/cacheflush.h>
+
+#define SCC_CFGREG19		0x120
+#define SCC_CFGREG20		0x124
+#define A15_CONF		0x400
+#define A7_CONF			0x500
+#define SYS_INFO		0x700
+#define PERF_LVL_A15		0xB00
+#define PERF_REQ_A15		0xB04
+#define PERF_LVL_A7		0xB08
+#define PERF_REQ_A7		0xB0c
+#define SYS_CFGCTRL		0xB10
+#define SYS_CFGCTRL_REQ		0xB14
+#define PWC_STATUS		0xB18
+#define PWC_FLAG		0xB1c
+#define WAKE_INT_MASK		0xB24
+#define WAKE_INT_RAW		0xB28
+#define WAKE_INT_STAT		0xB2c
+#define A15_PWRDN_EN		0xB30
+#define A7_PWRDN_EN		0xB34
+#define A7_PWRDNACK		0xB54
+#define A15_BX_ADDR0		0xB68
+#define SYS_CFG_WDATA		0xB70
+#define SYS_CFG_RDATA		0xB74
+#define A7_BX_ADDR0		0xB78
+
+#define GBL_WAKEUP_INT_MSK	(0x3 << 10)
+
+#define CLKF_SHIFT		16
+#define CLKF_MASK		0x1FFF
+#define CLKR_SHIFT		0
+#define CLKR_MASK		0x3F
+#define CLKOD_SHIFT		8
+#define CLKOD_MASK		0xF
+
+#define OPP_FUNCTION		6
+#define OPP_BASE_DEVICE		0x300
+#define OPP_A15_OFFSET		0x4
+#define OPP_A7_OFFSET		0xc
+
+#define SYS_CFGCTRL_START	(1 << 31)
+#define SYS_CFGCTRL_WRITE	(1 << 30)
+#define SYS_CFGCTRL_FUNC(n)	(((n) & 0x3f) << 20)
+#define SYS_CFGCTRL_DEVICE(n)	(((n) & 0xfff) << 0)
+/*
+ * Even though the SPC takes max 3-5 ms to complete any OPP/SYS_CFGCTRL
+ * operation, the operation could start just before jiffie is about
+ * to be incremented. So setting timeout value of 20ms = 2jiffies@100Hz
+ */
+#define TIME_OUT_US	20000
+
+#define MAX_OPPS	8
+#define MAX_CLUSTERS	2
+
+enum {
+	A15_OPP_STATUS		= 0,
+	A7_OPP_STATUS		= 1,
+	SYS_CFGCTRL_STATUS	= 2
+};
+
+#define STAT_COMPLETE(type)	((1 << 0) << (type << 2))
+#define STAT_ERR(type)		((1 << 1) << (type << 2))
+#define RESPONSE_MASK(type)	(STAT_COMPLETE(type) | STAT_ERR(type))
+
+struct vexpress_spc_drvdata {
+	void __iomem *baseaddr;
+	u32 a15_clusid;
+	int irq;
+	u32 cur_req_type;
+	u32 freqs[MAX_CLUSTERS][MAX_OPPS];
+	int freqs_cnt[MAX_CLUSTERS];
+};
+
+enum spc_func_type {
+	CONFIG_FUNC = 0,
+	PERF_FUNC   = 1,
+};
+
+struct vexpress_spc_func {
+	enum spc_func_type type;
+	u32 function;
+	u32 device;
+};
+
+static struct vexpress_spc_drvdata *info;
+static u32 *vexpress_spc_config_data;
+static struct vexpress_config_bridge *vexpress_spc_config_bridge;
+static struct vexpress_config_func *opp_func, *perf_func;
+
+static int vexpress_spc_load_result = -EAGAIN;
+static DEFINE_MUTEX(vexpress_spc_loading);
+
+static inline bool vexpress_spc_initialized(void)
+{
+	return vexpress_spc_load_result == 0;
+}
+
+/**
+ * vexpress_spc_write_resume_reg() - set the jump address used for warm boot
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @cpu: mpidr[7:0] bitfield describing cpu affinity level
+ * @addr: physical resume address
+ */
+void vexpress_spc_write_resume_reg(u32 cluster, u32 cpu, u32 addr)
+{
+	void __iomem *baseaddr;
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return;
+
+	if (cluster != info->a15_clusid)
+		baseaddr = info->baseaddr + A7_BX_ADDR0 + (cpu << 2);
+	else
+		baseaddr = info->baseaddr + A15_BX_ADDR0 + (cpu << 2);
+
+	writel_relaxed(addr, baseaddr);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_write_resume_reg);
+
+/**
+ * vexpress_spc_get_nb_cpus() - get number of cpus in a cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ *
+ * Return: number of cpus in the cluster
+ *         -EINVAL if cluster number invalid
+ */
+int vexpress_spc_get_nb_cpus(u32 cluster)
+{
+	u32 val;
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	val = readl_relaxed(info->baseaddr + SYS_INFO);
+	val = (cluster != info->a15_clusid) ? (val >> 20) : (val >> 16);
+	return val & 0xf;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_nb_cpus);
+
+/**
+ * vexpress_spc_get_performance - get current performance level of cluster
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: pointer to the performance level to be assigned
+ *
+ * Return: 0 on success
+ *         < 0 on read error
+ */
+int vexpress_spc_get_performance(u32 cluster, u32 *freq)
+{
+	u32 perf_cfg_reg;
+	int perf, ret;
+
+	if (!vexpress_spc_initialized() || (cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	perf_cfg_reg = cluster != info->a15_clusid ? PERF_LVL_A7 : PERF_LVL_A15;
+	ret = vexpress_config_read_timeout(perf_func, perf_cfg_reg,
+				&perf, usecs_to_jiffies(TIME_OUT_US));
+
+	if (!ret)
+		*freq = info->freqs[cluster][perf];
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_performance);
+
+/**
+ * vexpress_spc_get_perf_index - get performance level corresponding to
+ *				 a frequency
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: frequency to be looked-up
+ *
+ * Return: perf level index on success
+ *         -EINVAL on error
+ */
+static int vexpress_spc_find_perf_index(u32 cluster, u32 freq)
+{
+	int idx;
+
+	for (idx = 0; idx < info->freqs_cnt[cluster]; idx++)
+		if (info->freqs[cluster][idx] == freq)
+			break;
+	return (idx == info->freqs_cnt[cluster]) ? -EINVAL : idx;
+}
+
+/**
+ * vexpress_spc_set_performance - set current performance level of cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: performance level to be programmed
+ *
+ * Returns: 0 on success
+ *          < 0 on write error
+ */
+int vexpress_spc_set_performance(u32 cluster, u32 freq)
+{
+	int ret, perf, offset;
+
+	if (!vexpress_spc_initialized() || (cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	offset = (cluster != info->a15_clusid) ? PERF_LVL_A7 : PERF_LVL_A15;
+
+	perf = vexpress_spc_find_perf_index(cluster, freq);
+
+	if (perf < 0 || perf >= MAX_OPPS)
+		return -EINVAL;
+
+	ret = vexpress_config_write_timeout(perf_func, offset,
+			perf, usecs_to_jiffies(TIME_OUT_US));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_performance);
+
+static void vexpress_spc_set_wake_intr(u32 mask)
+{
+	writel_relaxed(mask & VEXPRESS_SPC_WAKE_INTR_MASK,
+	       info->baseaddr + WAKE_INT_MASK);
+}
+
+static inline void reg_bitmask(u32 *reg, u32 mask, bool set)
+{
+	if (set)
+		*reg |= mask;
+	else
+		*reg &= ~mask;
+}
+
+/**
+ * vexpress_spc_set_global_wakeup_intr()
+ *
+ * Function to set/clear global wakeup IRQs. Not protected by locking since
+ * it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @set: if true, global wake-up IRQs are set, if false they are cleared
+ *
+ */
+void vexpress_spc_set_global_wakeup_intr(bool set)
+{
+	u32 wake_int_mask_reg = 0;
+
+	wake_int_mask_reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
+	reg_bitmask(&wake_int_mask_reg, GBL_WAKEUP_INT_MSK, set);
+	vexpress_spc_set_wake_intr(wake_int_mask_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_global_wakeup_intr);
+
+/**
+ * vexpress_spc_set_cpu_wakeup_irq()
+ *
+ * Function to set/clear per-CPU wake-up IRQs. Not protected by locking since
+ * it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @cpu: mpidr[7:0] bitfield describing cpu affinity level
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @set: if true, wake-up IRQs are set, if false they are cleared
+ *
+ */
+void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster, bool set)
+{
+	u32 mask = 0;
+	u32 wake_int_mask_reg = 0;
+
+	mask = 1 << cpu;
+	if (info->a15_clusid != cluster)
+		mask <<= 4;
+
+	wake_int_mask_reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
+	reg_bitmask(&wake_int_mask_reg, mask, set);
+	vexpress_spc_set_wake_intr(wake_int_mask_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_cpu_wakeup_irq);
+
+/**
+ * vexpress_spc_powerdown_enable()
+ *
+ * Function to enable/disable cluster powerdown. Not protected by locking
+ * since it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @enable: if true enables powerdown, if false disables it
+ *
+ */
+void vexpress_spc_powerdown_enable(u32 cluster, bool enable)
+{
+	u32 pwdrn_reg = 0;
+
+	if (cluster >= MAX_CLUSTERS)
+		return;
+	pwdrn_reg = cluster != info->a15_clusid ? A7_PWRDN_EN : A15_PWRDN_EN;
+	writel_relaxed(enable, info->baseaddr + pwdrn_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_powerdown_enable);
+
+irqreturn_t vexpress_spc_irq_handler(int irq, void *data)
+{
+	int ret;
+	u32 status = readl_relaxed(info->baseaddr + PWC_STATUS);
+
+	if (!(status & RESPONSE_MASK(info->cur_req_type)))
+		return IRQ_NONE;
+
+	if ((status == STAT_COMPLETE(SYS_CFGCTRL_STATUS))
+			&& vexpress_spc_config_data) {
+		*vexpress_spc_config_data =
+				readl_relaxed(info->baseaddr + SYS_CFG_RDATA);
+		vexpress_spc_config_data = NULL;
+	}
+
+	ret = STAT_COMPLETE(info->cur_req_type) ? 0 : -EIO;
+	info->cur_req_type = 0;
+	vexpress_config_complete(vexpress_spc_config_bridge, ret);
+	return IRQ_HANDLED;
+}
+
+/**
+ * Based on the firmware documentation, this is always fixed to 20
+ * All the 4 OSC: A15 PLL0/1, A7 PLL0/1 must be programmed same
+ * values for both control and value registers.
+ * This function uses A15 PLL 0 registers to compute multiple factor
+ * F out = F in * (CLKF + 1) / ((CLKOD + 1) * (CLKR + 1))
+ */
+static inline int __get_mult_factor(void)
+{
+	int i_div, o_div, f_div;
+	u32 tmp;
+
+	tmp = readl(info->baseaddr + SCC_CFGREG19);
+	f_div = (tmp >> CLKF_SHIFT) & CLKF_MASK;
+
+	tmp = readl(info->baseaddr + SCC_CFGREG20);
+	o_div = (tmp >> CLKOD_SHIFT) & CLKOD_MASK;
+	i_div = (tmp >> CLKR_SHIFT) & CLKR_MASK;
+
+	return (f_div + 1) / ((o_div + 1) * (i_div + 1));
+}
+
+/**
+ * vexpress_spc_populate_opps() - initialize opp tables from microcontroller
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ *
+ * Return: 0 on success
+ *         < 0 on error
+ */
+static int vexpress_spc_populate_opps(u32 cluster)
+{
+	u32 data = 0, ret, i, offset;
+	int mult_fact = __get_mult_factor();
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	offset = cluster != info->a15_clusid ? OPP_A7_OFFSET : OPP_A15_OFFSET;
+	for (i = 0; i < MAX_OPPS; i++) {
+		ret = vexpress_config_read_timeout(opp_func, i + offset,
+				&data, usecs_to_jiffies(TIME_OUT_US));
+		if (!ret)
+			info->freqs[cluster][i] = (data & 0xFFFFF) * mult_fact;
+		else
+			break;
+	}
+
+	info->freqs_cnt[cluster] = i;
+	return ret;
+}
+
+/**
+ * vexpress_spc_get_freq_table() - Retrieve a pointer to the frequency
+ *				   table for a given cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @fptr: pointer to be initialized
+ * Return: operating points count on success
+ *         -EINVAL on pointer error
+ */
+int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr)
+{
+	if (WARN_ON_ONCE(!fptr || cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+	*fptr = info->freqs[cluster];
+	return info->freqs_cnt[cluster];
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_freq_table);
+
+static void *vexpress_spc_func_get(struct device *dev,
+		struct device_node *node, const char *id)
+{
+	struct vexpress_spc_func *spc_func;
+	u32 func_device[2];
+	int err = 0;
+
+	spc_func = kzalloc(sizeof(*spc_func), GFP_KERNEL);
+	if (!spc_func)
+		return NULL;
+
+	if (strcmp(id, "opp") == 0) {
+		spc_func->type = CONFIG_FUNC;
+		spc_func->function = OPP_FUNCTION;
+		spc_func->device = OPP_BASE_DEVICE;
+	} else if (strcmp(id, "perf") == 0) {
+		spc_func->type = PERF_FUNC;
+	} else if (node) {
+		of_node_get(node);
+		err = of_property_read_u32_array(node,
+				"arm,vexpress-sysreg,func", func_device,
+				ARRAY_SIZE(func_device));
+		of_node_put(node);
+		spc_func->type = CONFIG_FUNC;
+		spc_func->function = func_device[0];
+		spc_func->device = func_device[1];
+	}
+
+	if (WARN_ON(err)) {
+		kfree(spc_func);
+		return NULL;
+	}
+
+	pr_debug("func 0x%p = 0x%x, %d %d\n", spc_func,
+					     spc_func->function,
+					     spc_func->device,
+					     spc_func->type);
+
+	return spc_func;
+}
+
+static void vexpress_spc_func_put(void *func)
+{
+	kfree(func);
+}
+
+static int vexpress_spc_func_exec(void *func, int offset, bool write,
+				  u32 *data)
+{
+	struct vexpress_spc_func *spc_func = func;
+	u32 command;
+
+	/*
+	 * Setting and retrieval of operating points is not part of
+	 * DCC config interface. It was made to go through the same
+	 * code path so that requests to the M3 can be serialized
+	 * properly with config reads/writes through the common
+	 * vexpress config interface
+	 */
+	switch (spc_func->type) {
+	case PERF_FUNC:
+		if (write) {
+			info->cur_req_type = (offset == PERF_LVL_A15) ?
+					A15_OPP_STATUS : A7_OPP_STATUS;
+			writel_relaxed(*data, info->baseaddr + offset);
+			return VEXPRESS_CONFIG_STATUS_WAIT;
+		} else {
+			*data = readl_relaxed(info->baseaddr + offset);
+			return VEXPRESS_CONFIG_STATUS_DONE;
+		}
+	case CONFIG_FUNC:
+		info->cur_req_type = SYS_CFGCTRL_STATUS;
+
+		command = SYS_CFGCTRL_START;
+		command |= write ? SYS_CFGCTRL_WRITE : 0;
+		command |= SYS_CFGCTRL_FUNC(spc_func->function);
+		command |= SYS_CFGCTRL_DEVICE(spc_func->device + offset);
+
+		pr_debug("command %x\n", command);
+
+		if (!write)
+			vexpress_spc_config_data = data;
+		else
+			writel_relaxed(command, info->baseaddr + SYS_CFG_WDATA);
+		writel_relaxed(command, info->baseaddr + SYS_CFGCTRL);
+
+		return VEXPRESS_CONFIG_STATUS_WAIT;
+	default:
+		return -EINVAL;
+	}
+}
+
+struct vexpress_config_bridge_info vexpress_spc_config_bridge_info = {
+	.name = "vexpress-spc",
+	.func_get = vexpress_spc_func_get,
+	.func_put = vexpress_spc_func_put,
+	.func_exec = vexpress_spc_func_exec,
+};
+
+static const struct of_device_id vexpress_spc_ids[] __initconst = {
+	{ .compatible = "arm,vexpress-spc,v2p-ca15_a7" },
+	{ .compatible = "arm,vexpress-spc" },
+	{},
+};
+
+static int vexpress_spc_init(void)
+{
+	int ret;
+	struct device_node *node = of_find_matching_node(NULL,
+							 vexpress_spc_ids);
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		pr_err("%s: unable to allocate mem\n", __func__);
+		return -ENOMEM;
+	}
+
+	info->baseaddr = of_iomap(node, 0);
+	if (WARN_ON(!info->baseaddr)) {
+		ret = -ENXIO;
+		goto mem_free;
+	}
+
+	info->irq = irq_of_parse_and_map(node, 0);
+
+	if (WARN_ON(!info->irq)) {
+		ret = -ENXIO;
+		goto unmap;
+	}
+
+	readl_relaxed(info->baseaddr + PWC_STATUS);
+
+	ret = request_irq(info->irq, vexpress_spc_irq_handler,
+		IRQF_DISABLED | IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+		"arm-spc", info);
+
+	if (ret) {
+		pr_err("IRQ %d request failed\n", info->irq);
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	info->a15_clusid = readl_relaxed(info->baseaddr + A15_CONF) & 0xf;
+
+	vexpress_spc_config_bridge = vexpress_config_bridge_register(
+			node, &vexpress_spc_config_bridge_info);
+
+	if (WARN_ON(!vexpress_spc_config_bridge)) {
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	opp_func = vexpress_config_func_get(vexpress_spc_config_bridge, "opp");
+	perf_func =
+		vexpress_config_func_get(vexpress_spc_config_bridge, "perf");
+
+	if (!opp_func || !perf_func) {
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	if (vexpress_spc_populate_opps(0) || vexpress_spc_populate_opps(1)) {
+		if (info->irq)
+			free_irq(info->irq, info);
+		pr_err("failed to build OPP table\n");
+		ret = -ENODEV;
+		goto unmap;
+	}
+	/*
+	 * Multi-cluster systems may need this data when non-coherent, during
+	 * cluster power-up/power-down. Make sure it reaches main memory:
+	 */
+	sync_cache_w(info);
+	sync_cache_w(&info);
+	pr_info("vexpress-spc loaded at %p\n", info->baseaddr);
+	return 0;
+
+unmap:
+	iounmap(info->baseaddr);
+
+mem_free:
+	kfree(info);
+	return ret;
+}
+
+bool vexpress_spc_check_loaded(void)
+{
+	if (vexpress_spc_load_result != -EAGAIN)
+		return vexpress_spc_initialized();
+
+	mutex_lock(&vexpress_spc_loading);
+	if (vexpress_spc_load_result == -EAGAIN)
+		vexpress_spc_load_result = vexpress_spc_init();
+	mutex_unlock(&vexpress_spc_loading);
+	return vexpress_spc_initialized();
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_check_loaded);
+
+static int __init vexpress_spc_early_init(void)
+{
+	vexpress_spc_check_loaded();
+	return vexpress_spc_load_result;
+}
+early_initcall(vexpress_spc_early_init);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Serial Power Controller (SPC) support");
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index e5015d8..15cc123 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -147,4 +147,47 @@ void vexpress_clk_of_register_spc(void);
 void vexpress_clk_init(void __iomem *sp810_base);
 void vexpress_clk_of_init(void);
 
+/* SPC */
+
+#define	VEXPRESS_SPC_WAKE_INTR_IRQ(cluster, cpu) \
+			(1 << (4 * (cluster) + (cpu)))
+#define	VEXPRESS_SPC_WAKE_INTR_FIQ(cluster, cpu) \
+			(1 << (7 * (cluster) + (cpu)))
+#define	VEXPRESS_SPC_WAKE_INTR_SWDOG		(1 << 10)
+#define	VEXPRESS_SPC_WAKE_INTR_GTIMER		(1 << 11)
+#define	VEXPRESS_SPC_WAKE_INTR_MASK		0xFFF
+
+#ifdef CONFIG_VEXPRESS_SPC
+extern bool vexpress_spc_check_loaded(void);
+extern void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster, bool set);
+extern void vexpress_spc_set_global_wakeup_intr(bool set);
+extern int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr);
+extern int vexpress_spc_get_performance(u32 cluster, u32 *freq);
+extern int vexpress_spc_set_performance(u32 cluster, u32 freq);
+extern void vexpress_spc_write_resume_reg(u32 cluster, u32 cpu, u32 addr);
+extern int vexpress_spc_get_nb_cpus(u32 cluster);
+extern void vexpress_spc_powerdown_enable(u32 cluster, bool enable);
+#else
+static inline bool vexpress_spc_check_loaded(void) { return false; }
+static inline void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster,
+						   bool set) { }
+static inline void vexpress_spc_set_global_wakeup_intr(bool set) { }
+static inline int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr)
+{
+	return -ENODEV;
+}
+static inline int vexpress_spc_get_performance(u32 cluster, u32 *freq)
+{
+	return -ENODEV;
+}
+static inline int vexpress_spc_set_performance(u32 cluster, u32 freq)
+{
+	return -ENODEV;
+}
+static inline void vexpress_spc_write_resume_reg(u32 cluster,
+						 u32 cpu, u32 addr) { }
+static inline int vexpress_spc_get_nb_cpus(u32 cluster) { return -ENODEV; }
+static inline void vexpress_spc_powerdown_enable(u32 cluster, bool enable) { }
+#endif
+
 #endif
-- 
1.8.2.2

[RFC PATCH 3/3] drivers: mfd: vexpress: add Serial Power Controller (SPC) support

[Lorenzo Pieralisi]

The TC2 versatile express core tile integrates a logic block that provides the
interface between the dual cluster test-chip and the M3 microcontroller that
carries out power management. The logic block, called Serial Power Controller
(SPC), contains several memory mapped registers to control among other things
low-power states, operating points and reset control.

This patch provides a driver that enables run-time control of features
implemented by the SPC control logic.

The driver also provides a bridge interface through the vexpress config
infrastructure. Operations allowing to read/write operating points are
made to go via the same interface as configuration transactions so that
all requests to M3 are serialized.

Device tree bindings documentation for the SPC component are provided with
the patchset.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
---
 Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  35 +
 drivers/mfd/Kconfig                                    |   7 +
 drivers/mfd/Makefile                                   |   1 +
 drivers/mfd/vexpress-spc.c                             | 626 ++++++++++
 include/linux/vexpress.h                               |  43 +
 5 files changed, 712 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/vexpress-spc.txt b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
new file mode 100644
index 0000000..1d71dc2
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
@@ -0,0 +1,35 @@
+* ARM Versatile Express Serial Power Controller device tree bindings
+
+Latest ARM development boards implement a power management interface (serial
+power controller - SPC) that is capable of managing power/voltage and
+operating point transitions, through memory mapped registers interface.
+
+On testchips like TC2 it also provides a configuration interface that can
+be used to read/write values which cannot be read/written through simple
+memory mapped reads/writes.
+
+- spc node
+
+	- compatible:
+		Usage: required
+		Value type: <stringlist>
+		Definition: must be
+			    "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc"
+	- reg:
+		Usage: required
+		Value type: <prop-encode-array>
+		Definition: A standard property that specifies the base address
+			    and the size of the SPC address space
+	- interrupts:
+		Usage: required
+		Value type: <prop-encoded-array>
+		Definition:  SPC interrupt configuration. A standard property
+			     that follows ePAPR interrupts specifications
+
+Example:
+
+spc: spc at 7fff0000 {
+	compatible = "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc";
+	reg = <0 0x7FFF0000 0 0x1000>;
+	interrupts = <0 95 4>;
+};
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index d9aed15..b5259af 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1147,3 +1147,10 @@ config VEXPRESS_CONFIG
 	help
 	  Platform configuration infrastructure for the ARM Ltd.
 	  Versatile Express.
+
+config VEXPRESS_SPC
+	bool "Versatile Express SPC driver support"
+	depends on ARM
+	depends on VEXPRESS_CONFIG
+	help
+	  Serial Power Controller driver for ARM Ltd. test chips.
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 718e94a..3a01203 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -153,5 +153,6 @@ obj-$(CONFIG_MFD_SEC_CORE)	+= sec-core.o sec-irq.o
 obj-$(CONFIG_MFD_SYSCON)	+= syscon.o
 obj-$(CONFIG_MFD_LM3533)	+= lm3533-core.o lm3533-ctrlbank.o
 obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o vexpress-sysreg.o
+obj-$(CONFIG_VEXPRESS_SPC)	+= vexpress-spc.o
 obj-$(CONFIG_MFD_RETU)		+= retu-mfd.o
 obj-$(CONFIG_MFD_AS3711)	+= as3711.o
diff --git a/drivers/mfd/vexpress-spc.c b/drivers/mfd/vexpress-spc.c
new file mode 100644
index 0000000..f78257a
--- /dev/null
+++ b/drivers/mfd/vexpress-spc.c
@@ -0,0 +1,626 @@
+/*
+ * Versatile Express Serial Power Controller (SPC) support
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ *
+ * Author(s): Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+ *            Achin Gupta           <achin.gupta@arm.com>
+ *            Lorenzo Pieralisi     <lorenzo.pieralisi@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+#include <linux/vexpress.h>
+
+#include <asm/cacheflush.h>
+
+#define SCC_CFGREG19		0x120
+#define SCC_CFGREG20		0x124
+#define A15_CONF		0x400
+#define A7_CONF			0x500
+#define SYS_INFO		0x700
+#define PERF_LVL_A15		0xB00
+#define PERF_REQ_A15		0xB04
+#define PERF_LVL_A7		0xB08
+#define PERF_REQ_A7		0xB0c
+#define SYS_CFGCTRL		0xB10
+#define SYS_CFGCTRL_REQ		0xB14
+#define PWC_STATUS		0xB18
+#define PWC_FLAG		0xB1c
+#define WAKE_INT_MASK		0xB24
+#define WAKE_INT_RAW		0xB28
+#define WAKE_INT_STAT		0xB2c
+#define A15_PWRDN_EN		0xB30
+#define A7_PWRDN_EN		0xB34
+#define A7_PWRDNACK		0xB54
+#define A15_BX_ADDR0		0xB68
+#define SYS_CFG_WDATA		0xB70
+#define SYS_CFG_RDATA		0xB74
+#define A7_BX_ADDR0		0xB78
+
+#define GBL_WAKEUP_INT_MSK	(0x3 << 10)
+
+#define CLKF_SHIFT		16
+#define CLKF_MASK		0x1FFF
+#define CLKR_SHIFT		0
+#define CLKR_MASK		0x3F
+#define CLKOD_SHIFT		8
+#define CLKOD_MASK		0xF
+
+#define OPP_FUNCTION		6
+#define OPP_BASE_DEVICE		0x300
+#define OPP_A15_OFFSET		0x4
+#define OPP_A7_OFFSET		0xc
+
+#define SYS_CFGCTRL_START	(1 << 31)
+#define SYS_CFGCTRL_WRITE	(1 << 30)
+#define SYS_CFGCTRL_FUNC(n)	(((n) & 0x3f) << 20)
+#define SYS_CFGCTRL_DEVICE(n)	(((n) & 0xfff) << 0)
+/*
+ * Even though the SPC takes max 3-5 ms to complete any OPP/SYS_CFGCTRL
+ * operation, the operation could start just before jiffie is about
+ * to be incremented. So setting timeout value of 20ms = 2jiffies@100Hz
+ */
+#define TIME_OUT_US	20000
+
+#define MAX_OPPS	8
+#define MAX_CLUSTERS	2
+
+enum {
+	A15_OPP_STATUS		= 0,
+	A7_OPP_STATUS		= 1,
+	SYS_CFGCTRL_STATUS	= 2
+};
+
+#define STAT_COMPLETE(type)	((1 << 0) << (type << 2))
+#define STAT_ERR(type)		((1 << 1) << (type << 2))
+#define RESPONSE_MASK(type)	(STAT_COMPLETE(type) | STAT_ERR(type))
+
+struct vexpress_spc_drvdata {
+	void __iomem *baseaddr;
+	u32 a15_clusid;
+	int irq;
+	u32 cur_req_type;
+	u32 freqs[MAX_CLUSTERS][MAX_OPPS];
+	int freqs_cnt[MAX_CLUSTERS];
+};
+
+enum spc_func_type {
+	CONFIG_FUNC = 0,
+	PERF_FUNC   = 1,
+};
+
+struct vexpress_spc_func {
+	enum spc_func_type type;
+	u32 function;
+	u32 device;
+};
+
+static struct vexpress_spc_drvdata *info;
+static u32 *vexpress_spc_config_data;
+static struct vexpress_config_bridge *vexpress_spc_config_bridge;
+static struct vexpress_config_func *opp_func, *perf_func;
+
+static int vexpress_spc_load_result = -EAGAIN;
+static DEFINE_MUTEX(vexpress_spc_loading);
+
+static inline bool vexpress_spc_initialized(void)
+{
+	return vexpress_spc_load_result == 0;
+}
+
+/**
+ * vexpress_spc_write_resume_reg() - set the jump address used for warm boot
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @cpu: mpidr[7:0] bitfield describing cpu affinity level
+ * @addr: physical resume address
+ */
+void vexpress_spc_write_resume_reg(u32 cluster, u32 cpu, u32 addr)
+{
+	void __iomem *baseaddr;
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return;
+
+	if (cluster != info->a15_clusid)
+		baseaddr = info->baseaddr + A7_BX_ADDR0 + (cpu << 2);
+	else
+		baseaddr = info->baseaddr + A15_BX_ADDR0 + (cpu << 2);
+
+	writel_relaxed(addr, baseaddr);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_write_resume_reg);
+
+/**
+ * vexpress_spc_get_nb_cpus() - get number of cpus in a cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ *
+ * Return: number of cpus in the cluster
+ *         -EINVAL if cluster number invalid
+ */
+int vexpress_spc_get_nb_cpus(u32 cluster)
+{
+	u32 val;
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	val = readl_relaxed(info->baseaddr + SYS_INFO);
+	val = (cluster != info->a15_clusid) ? (val >> 20) : (val >> 16);
+	return val & 0xf;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_nb_cpus);
+
+/**
+ * vexpress_spc_get_performance - get current performance level of cluster
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: pointer to the performance level to be assigned
+ *
+ * Return: 0 on success
+ *         < 0 on read error
+ */
+int vexpress_spc_get_performance(u32 cluster, u32 *freq)
+{
+	u32 perf_cfg_reg;
+	int perf, ret;
+
+	if (!vexpress_spc_initialized() || (cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	perf_cfg_reg = cluster != info->a15_clusid ? PERF_LVL_A7 : PERF_LVL_A15;
+	ret = vexpress_config_read_timeout(perf_func, perf_cfg_reg,
+				&perf, usecs_to_jiffies(TIME_OUT_US));
+
+	if (!ret)
+		*freq = info->freqs[cluster][perf];
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_performance);
+
+/**
+ * vexpress_spc_get_perf_index - get performance level corresponding to
+ *				 a frequency
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: frequency to be looked-up
+ *
+ * Return: perf level index on success
+ *         -EINVAL on error
+ */
+static int vexpress_spc_find_perf_index(u32 cluster, u32 freq)
+{
+	int idx;
+
+	for (idx = 0; idx < info->freqs_cnt[cluster]; idx++)
+		if (info->freqs[cluster][idx] == freq)
+			break;
+	return (idx == info->freqs_cnt[cluster]) ? -EINVAL : idx;
+}
+
+/**
+ * vexpress_spc_set_performance - set current performance level of cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @freq: performance level to be programmed
+ *
+ * Returns: 0 on success
+ *          < 0 on write error
+ */
+int vexpress_spc_set_performance(u32 cluster, u32 freq)
+{
+	int ret, perf, offset;
+
+	if (!vexpress_spc_initialized() || (cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	offset = (cluster != info->a15_clusid) ? PERF_LVL_A7 : PERF_LVL_A15;
+
+	perf = vexpress_spc_find_perf_index(cluster, freq);
+
+	if (perf < 0 || perf >= MAX_OPPS)
+		return -EINVAL;
+
+	ret = vexpress_config_write_timeout(perf_func, offset,
+			perf, usecs_to_jiffies(TIME_OUT_US));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_performance);
+
+static void vexpress_spc_set_wake_intr(u32 mask)
+{
+	writel_relaxed(mask & VEXPRESS_SPC_WAKE_INTR_MASK,
+	       info->baseaddr + WAKE_INT_MASK);
+}
+
+static inline void reg_bitmask(u32 *reg, u32 mask, bool set)
+{
+	if (set)
+		*reg |= mask;
+	else
+		*reg &= ~mask;
+}
+
+/**
+ * vexpress_spc_set_global_wakeup_intr()
+ *
+ * Function to set/clear global wakeup IRQs. Not protected by locking since
+ * it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @set: if true, global wake-up IRQs are set, if false they are cleared
+ *
+ */
+void vexpress_spc_set_global_wakeup_intr(bool set)
+{
+	u32 wake_int_mask_reg = 0;
+
+	wake_int_mask_reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
+	reg_bitmask(&wake_int_mask_reg, GBL_WAKEUP_INT_MSK, set);
+	vexpress_spc_set_wake_intr(wake_int_mask_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_global_wakeup_intr);
+
+/**
+ * vexpress_spc_set_cpu_wakeup_irq()
+ *
+ * Function to set/clear per-CPU wake-up IRQs. Not protected by locking since
+ * it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @cpu: mpidr[7:0] bitfield describing cpu affinity level
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @set: if true, wake-up IRQs are set, if false they are cleared
+ *
+ */
+void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster, bool set)
+{
+	u32 mask = 0;
+	u32 wake_int_mask_reg = 0;
+
+	mask = 1 << cpu;
+	if (info->a15_clusid != cluster)
+		mask <<= 4;
+
+	wake_int_mask_reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
+	reg_bitmask(&wake_int_mask_reg, mask, set);
+	vexpress_spc_set_wake_intr(wake_int_mask_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_set_cpu_wakeup_irq);
+
+/**
+ * vexpress_spc_powerdown_enable()
+ *
+ * Function to enable/disable cluster powerdown. Not protected by locking
+ * since it might be used in code paths where normal cacheable locks are not
+ * working. Locking must be provided by the caller to ensure atomicity.
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @enable: if true enables powerdown, if false disables it
+ *
+ */
+void vexpress_spc_powerdown_enable(u32 cluster, bool enable)
+{
+	u32 pwdrn_reg = 0;
+
+	if (cluster >= MAX_CLUSTERS)
+		return;
+	pwdrn_reg = cluster != info->a15_clusid ? A7_PWRDN_EN : A15_PWRDN_EN;
+	writel_relaxed(enable, info->baseaddr + pwdrn_reg);
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_powerdown_enable);
+
+irqreturn_t vexpress_spc_irq_handler(int irq, void *data)
+{
+	int ret;
+	u32 status = readl_relaxed(info->baseaddr + PWC_STATUS);
+
+	if (!(status & RESPONSE_MASK(info->cur_req_type)))
+		return IRQ_NONE;
+
+	if ((status == STAT_COMPLETE(SYS_CFGCTRL_STATUS))
+			&& vexpress_spc_config_data) {
+		*vexpress_spc_config_data =
+				readl_relaxed(info->baseaddr + SYS_CFG_RDATA);
+		vexpress_spc_config_data = NULL;
+	}
+
+	ret = STAT_COMPLETE(info->cur_req_type) ? 0 : -EIO;
+	info->cur_req_type = 0;
+	vexpress_config_complete(vexpress_spc_config_bridge, ret);
+	return IRQ_HANDLED;
+}
+
+/**
+ * Based on the firmware documentation, this is always fixed to 20
+ * All the 4 OSC: A15 PLL0/1, A7 PLL0/1 must be programmed same
+ * values for both control and value registers.
+ * This function uses A15 PLL 0 registers to compute multiple factor
+ * F out = F in * (CLKF + 1) / ((CLKOD + 1) * (CLKR + 1))
+ */
+static inline int __get_mult_factor(void)
+{
+	int i_div, o_div, f_div;
+	u32 tmp;
+
+	tmp = readl(info->baseaddr + SCC_CFGREG19);
+	f_div = (tmp >> CLKF_SHIFT) & CLKF_MASK;
+
+	tmp = readl(info->baseaddr + SCC_CFGREG20);
+	o_div = (tmp >> CLKOD_SHIFT) & CLKOD_MASK;
+	i_div = (tmp >> CLKR_SHIFT) & CLKR_MASK;
+
+	return (f_div + 1) / ((o_div + 1) * (i_div + 1));
+}
+
+/**
+ * vexpress_spc_populate_opps() - initialize opp tables from microcontroller
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ *
+ * Return: 0 on success
+ *         < 0 on error
+ */
+static int vexpress_spc_populate_opps(u32 cluster)
+{
+	u32 data = 0, ret, i, offset;
+	int mult_fact = __get_mult_factor();
+
+	if (WARN_ON_ONCE(cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+
+	offset = cluster != info->a15_clusid ? OPP_A7_OFFSET : OPP_A15_OFFSET;
+	for (i = 0; i < MAX_OPPS; i++) {
+		ret = vexpress_config_read_timeout(opp_func, i + offset,
+				&data, usecs_to_jiffies(TIME_OUT_US));
+		if (!ret)
+			info->freqs[cluster][i] = (data & 0xFFFFF) * mult_fact;
+		else
+			break;
+	}
+
+	info->freqs_cnt[cluster] = i;
+	return ret;
+}
+
+/**
+ * vexpress_spc_get_freq_table() - Retrieve a pointer to the frequency
+ *				   table for a given cluster
+ *
+ * @cluster: mpidr[15:8] bitfield describing cluster affinity level
+ * @fptr: pointer to be initialized
+ * Return: operating points count on success
+ *         -EINVAL on pointer error
+ */
+int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr)
+{
+	if (WARN_ON_ONCE(!fptr || cluster >= MAX_CLUSTERS))
+		return -EINVAL;
+	*fptr = info->freqs[cluster];
+	return info->freqs_cnt[cluster];
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_get_freq_table);
+
+static void *vexpress_spc_func_get(struct device *dev,
+		struct device_node *node, const char *id)
+{
+	struct vexpress_spc_func *spc_func;
+	u32 func_device[2];
+	int err = 0;
+
+	spc_func = kzalloc(sizeof(*spc_func), GFP_KERNEL);
+	if (!spc_func)
+		return NULL;
+
+	if (strcmp(id, "opp") == 0) {
+		spc_func->type = CONFIG_FUNC;
+		spc_func->function = OPP_FUNCTION;
+		spc_func->device = OPP_BASE_DEVICE;
+	} else if (strcmp(id, "perf") == 0) {
+		spc_func->type = PERF_FUNC;
+	} else if (node) {
+		of_node_get(node);
+		err = of_property_read_u32_array(node,
+				"arm,vexpress-sysreg,func", func_device,
+				ARRAY_SIZE(func_device));
+		of_node_put(node);
+		spc_func->type = CONFIG_FUNC;
+		spc_func->function = func_device[0];
+		spc_func->device = func_device[1];
+	}
+
+	if (WARN_ON(err)) {
+		kfree(spc_func);
+		return NULL;
+	}
+
+	pr_debug("func 0x%p = 0x%x, %d %d\n", spc_func,
+					     spc_func->function,
+					     spc_func->device,
+					     spc_func->type);
+
+	return spc_func;
+}
+
+static void vexpress_spc_func_put(void *func)
+{
+	kfree(func);
+}
+
+static int vexpress_spc_func_exec(void *func, int offset, bool write,
+				  u32 *data)
+{
+	struct vexpress_spc_func *spc_func = func;
+	u32 command;
+
+	/*
+	 * Setting and retrieval of operating points is not part of
+	 * DCC config interface. It was made to go through the same
+	 * code path so that requests to the M3 can be serialized
+	 * properly with config reads/writes through the common
+	 * vexpress config interface
+	 */
+	switch (spc_func->type) {
+	case PERF_FUNC:
+		if (write) {
+			info->cur_req_type = (offset == PERF_LVL_A15) ?
+					A15_OPP_STATUS : A7_OPP_STATUS;
+			writel_relaxed(*data, info->baseaddr + offset);
+			return VEXPRESS_CONFIG_STATUS_WAIT;
+		} else {
+			*data = readl_relaxed(info->baseaddr + offset);
+			return VEXPRESS_CONFIG_STATUS_DONE;
+		}
+	case CONFIG_FUNC:
+		info->cur_req_type = SYS_CFGCTRL_STATUS;
+
+		command = SYS_CFGCTRL_START;
+		command |= write ? SYS_CFGCTRL_WRITE : 0;
+		command |= SYS_CFGCTRL_FUNC(spc_func->function);
+		command |= SYS_CFGCTRL_DEVICE(spc_func->device + offset);
+
+		pr_debug("command %x\n", command);
+
+		if (!write)
+			vexpress_spc_config_data = data;
+		else
+			writel_relaxed(command, info->baseaddr + SYS_CFG_WDATA);
+		writel_relaxed(command, info->baseaddr + SYS_CFGCTRL);
+
+		return VEXPRESS_CONFIG_STATUS_WAIT;
+	default:
+		return -EINVAL;
+	}
+}
+
+struct vexpress_config_bridge_info vexpress_spc_config_bridge_info = {
+	.name = "vexpress-spc",
+	.func_get = vexpress_spc_func_get,
+	.func_put = vexpress_spc_func_put,
+	.func_exec = vexpress_spc_func_exec,
+};
+
+static const struct of_device_id vexpress_spc_ids[] __initconst = {
+	{ .compatible = "arm,vexpress-spc,v2p-ca15_a7" },
+	{ .compatible = "arm,vexpress-spc" },
+	{},
+};
+
+static int vexpress_spc_init(void)
+{
+	int ret;
+	struct device_node *node = of_find_matching_node(NULL,
+							 vexpress_spc_ids);
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		pr_err("%s: unable to allocate mem\n", __func__);
+		return -ENOMEM;
+	}
+
+	info->baseaddr = of_iomap(node, 0);
+	if (WARN_ON(!info->baseaddr)) {
+		ret = -ENXIO;
+		goto mem_free;
+	}
+
+	info->irq = irq_of_parse_and_map(node, 0);
+
+	if (WARN_ON(!info->irq)) {
+		ret = -ENXIO;
+		goto unmap;
+	}
+
+	readl_relaxed(info->baseaddr + PWC_STATUS);
+
+	ret = request_irq(info->irq, vexpress_spc_irq_handler,
+		IRQF_DISABLED | IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+		"arm-spc", info);
+
+	if (ret) {
+		pr_err("IRQ %d request failed\n", info->irq);
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	info->a15_clusid = readl_relaxed(info->baseaddr + A15_CONF) & 0xf;
+
+	vexpress_spc_config_bridge = vexpress_config_bridge_register(
+			node, &vexpress_spc_config_bridge_info);
+
+	if (WARN_ON(!vexpress_spc_config_bridge)) {
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	opp_func = vexpress_config_func_get(vexpress_spc_config_bridge, "opp");
+	perf_func =
+		vexpress_config_func_get(vexpress_spc_config_bridge, "perf");
+
+	if (!opp_func || !perf_func) {
+		ret = -ENODEV;
+		goto unmap;
+	}
+
+	if (vexpress_spc_populate_opps(0) || vexpress_spc_populate_opps(1)) {
+		if (info->irq)
+			free_irq(info->irq, info);
+		pr_err("failed to build OPP table\n");
+		ret = -ENODEV;
+		goto unmap;
+	}
+	/*
+	 * Multi-cluster systems may need this data when non-coherent, during
+	 * cluster power-up/power-down. Make sure it reaches main memory:
+	 */
+	sync_cache_w(info);
+	sync_cache_w(&info);
+	pr_info("vexpress-spc loaded at %p\n", info->baseaddr);
+	return 0;
+
+unmap:
+	iounmap(info->baseaddr);
+
+mem_free:
+	kfree(info);
+	return ret;
+}
+
+bool vexpress_spc_check_loaded(void)
+{
+	if (vexpress_spc_load_result != -EAGAIN)
+		return vexpress_spc_initialized();
+
+	mutex_lock(&vexpress_spc_loading);
+	if (vexpress_spc_load_result == -EAGAIN)
+		vexpress_spc_load_result = vexpress_spc_init();
+	mutex_unlock(&vexpress_spc_loading);
+	return vexpress_spc_initialized();
+}
+EXPORT_SYMBOL_GPL(vexpress_spc_check_loaded);
+
+static int __init vexpress_spc_early_init(void)
+{
+	vexpress_spc_check_loaded();
+	return vexpress_spc_load_result;
+}
+early_initcall(vexpress_spc_early_init);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Serial Power Controller (SPC) support");
diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
index e5015d8..15cc123 100644
--- a/include/linux/vexpress.h
+++ b/include/linux/vexpress.h
@@ -147,4 +147,47 @@ void vexpress_clk_of_register_spc(void);
 void vexpress_clk_init(void __iomem *sp810_base);
 void vexpress_clk_of_init(void);
 
+/* SPC */
+
+#define	VEXPRESS_SPC_WAKE_INTR_IRQ(cluster, cpu) \
+			(1 << (4 * (cluster) + (cpu)))
+#define	VEXPRESS_SPC_WAKE_INTR_FIQ(cluster, cpu) \
+			(1 << (7 * (cluster) + (cpu)))
+#define	VEXPRESS_SPC_WAKE_INTR_SWDOG		(1 << 10)
+#define	VEXPRESS_SPC_WAKE_INTR_GTIMER		(1 << 11)
+#define	VEXPRESS_SPC_WAKE_INTR_MASK		0xFFF
+
+#ifdef CONFIG_VEXPRESS_SPC
+extern bool vexpress_spc_check_loaded(void);
+extern void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster, bool set);
+extern void vexpress_spc_set_global_wakeup_intr(bool set);
+extern int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr);
+extern int vexpress_spc_get_performance(u32 cluster, u32 *freq);
+extern int vexpress_spc_set_performance(u32 cluster, u32 freq);
+extern void vexpress_spc_write_resume_reg(u32 cluster, u32 cpu, u32 addr);
+extern int vexpress_spc_get_nb_cpus(u32 cluster);
+extern void vexpress_spc_powerdown_enable(u32 cluster, bool enable);
+#else
+static inline bool vexpress_spc_check_loaded(void) { return false; }
+static inline void vexpress_spc_set_cpu_wakeup_irq(u32 cpu, u32 cluster,
+						   bool set) { }
+static inline void vexpress_spc_set_global_wakeup_intr(bool set) { }
+static inline int vexpress_spc_get_freq_table(u32 cluster, u32 **fptr)
+{
+	return -ENODEV;
+}
+static inline int vexpress_spc_get_performance(u32 cluster, u32 *freq)
+{
+	return -ENODEV;
+}
+static inline int vexpress_spc_set_performance(u32 cluster, u32 freq)
+{
+	return -ENODEV;
+}
+static inline void vexpress_spc_write_resume_reg(u32 cluster,
+						 u32 cpu, u32 addr) { }
+static inline int vexpress_spc_get_nb_cpus(u32 cluster) { return -ENODEV; }
+static inline void vexpress_spc_powerdown_enable(u32 cluster, bool enable) { }
+#endif
+
 #endif
-- 
1.8.2.2