[PATCH v4 0/6] Make deferring probe forever optional

[PATCH v4 0/6] Make deferring probe forever optional

[Rob Herring]

This series came out of a discussion on the ARM boot-architecture
list[1] about DT forwards and backwards compatibility issues. There are
issues with newer DTs breaking on older, stable kernels. Some of these
are difficult to solve, but cases of optional devices not having
kernel support should be solvable.

I tested this on a RPi3 B with the pinctrl driver forced off. With this
change, the MMC/SD and UART drivers can function without the pinctrl
driver. I left the dts change out this time.

v2 and v3 of this series can be found here[2][3].

Rob

[1] https://lists.linaro.org/pipermail/boot-architecture/2018-April/000466.html
[2] https://lore.kernel.org/patchwork/project/lkml/list/?series=347413
[3] https://lore.kernel.org/patchwork/project/lkml/list/?series=357344

Rob Herring (6):
  driver core: allow stopping deferred probe after init
  dt-bindings: pinctrl: add a 'pinctrl-use-default' property
  pinctrl: Support stopping deferred probe after initcalls
  iommu: Stop deferring probe at end of initcalls
  iommu: Remove IOMMU_OF_DECLARE
  PM / Domains: Stop deferring probe at the end of initcall

 .../admin-guide/kernel-parameters.txt         |  9 +++
 .../bindings/pinctrl/pinctrl-bindings.txt     |  6 ++
 drivers/base/dd.c                             | 59 +++++++++++++++++++
 drivers/base/power/domain.c                   |  2 +-
 drivers/iommu/arm-smmu-v3.c                   |  2 -
 drivers/iommu/arm-smmu.c                      |  7 ---
 drivers/iommu/exynos-iommu.c                  |  2 -
 drivers/iommu/ipmmu-vmsa.c                    |  3 -
 drivers/iommu/msm_iommu.c                     |  2 -
 drivers/iommu/of_iommu.c                      | 21 +------
 drivers/iommu/qcom_iommu.c                    |  2 -
 drivers/iommu/rockchip-iommu.c                |  2 -
 drivers/pinctrl/devicetree.c                  | 15 +++--
 include/asm-generic/vmlinux.lds.h             |  2 -
 include/linux/device.h                        |  2 +
 include/linux/of_iommu.h                      |  4 --
 16 files changed, 90 insertions(+), 50 deletions(-)

--
2.17.1

[PATCH v4 0/6] Make deferring probe forever optional

[Rob Herring]

This series came out of a discussion on the ARM boot-architecture
list[1] about DT forwards and backwards compatibility issues. There are
issues with newer DTs breaking on older, stable kernels. Some of these
are difficult to solve, but cases of optional devices not having
kernel support should be solvable.

I tested this on a RPi3 B with the pinctrl driver forced off. With this
change, the MMC/SD and UART drivers can function without the pinctrl
driver. I left the dts change out this time.

v2 and v3 of this series can be found here[2][3].

Rob

[1] https://lists.linaro.org/pipermail/boot-architecture/2018-April/000466.html
[2] https://lore.kernel.org/patchwork/project/lkml/list/?series=347413
[3] https://lore.kernel.org/patchwork/project/lkml/list/?series=357344

Rob Herring (6):
  driver core: allow stopping deferred probe after init
  dt-bindings: pinctrl: add a 'pinctrl-use-default' property
  pinctrl: Support stopping deferred probe after initcalls
  iommu: Stop deferring probe at end of initcalls
  iommu: Remove IOMMU_OF_DECLARE
  PM / Domains: Stop deferring probe at the end of initcall

 .../admin-guide/kernel-parameters.txt         |  9 +++
 .../bindings/pinctrl/pinctrl-bindings.txt     |  6 ++
 drivers/base/dd.c                             | 59 +++++++++++++++++++
 drivers/base/power/domain.c                   |  2 +-
 drivers/iommu/arm-smmu-v3.c                   |  2 -
 drivers/iommu/arm-smmu.c                      |  7 ---
 drivers/iommu/exynos-iommu.c                  |  2 -
 drivers/iommu/ipmmu-vmsa.c                    |  3 -
 drivers/iommu/msm_iommu.c                     |  2 -
 drivers/iommu/of_iommu.c                      | 21 +------
 drivers/iommu/qcom_iommu.c                    |  2 -
 drivers/iommu/rockchip-iommu.c                |  2 -
 drivers/pinctrl/devicetree.c                  | 15 +++--
 include/asm-generic/vmlinux.lds.h             |  2 -
 include/linux/device.h                        |  2 +
 include/linux/of_iommu.h                      |  4 --
 16 files changed, 90 insertions(+), 50 deletions(-)

--
2.17.1

[PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Rob Herring]

Deferred probe will currently wait forever on dependent devices to probe,
but sometimes a driver will never exist. It's also not always critical for
a driver to exist. Platforms can rely on default configuration from the
bootloader or reset defaults for things such as pinctrl and power domains.
This is often the case with initial platform support until various drivers
get enabled. There's at least 2 scenarios where deferred probe can render
a platform broken. Both involve using a DT which has more devices and
dependencies than the kernel supports. The 1st case is a driver may be
disabled in the kernel config. The 2nd case is the kernel version may
simply not have the dependent driver. This can happen if using a newer DT
(provided by firmware perhaps) with a stable kernel version. Deferred
probe issues can be difficult to debug especially if the console has
dependencies or userspace fails to boot to a shell.

There are also cases like IOMMUs where only built-in drivers are
supported, so deferring probe after initcalls is not needed. The IOMMU
subsystem implemented its own mechanism to handle this using OF_DECLARE
linker sections.

This commit adds makes ending deferred probe conditional on initcalls
being completed or a debug timeout. Subsystems or drivers may opt-in by
calling driver_deferred_probe_check_init_done() instead of
unconditionally returning -EPROBE_DEFER. They may use additional
information from DT or kernel's config to decide whether to continue to
defer probe or not.

The timeout mechanism is intended for debug purposes and WARNs loudly.
The remaining deferred probe pending list will also be dumped after the
timeout. Not that this timeout won't work for the console which needs
to be enabled before userspace starts. However, if the console's
dependencies are resolved, then the kernel log will be printed (as
opposed to no output).

Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
- Rebase on driver-core-next
- Only allow base 10 for timeout

v3:
- Merged with timeout patch.
- Clarify that deferred_probe_timeout is a debug option.
- Drop the 'optional' param. The only user was pinctrl, so it has to handle
  that functionality.
- Rename function to driver_deferred_probe_check_state
- Added kerneldoc for driver_deferred_probe_check_state
- Print a 1 line warning if stopping deferred probe after initcalls and a
  WARN on timeout.

 .../admin-guide/kernel-parameters.txt         |  9 +++
 drivers/base/dd.c                             | 59 +++++++++++++++++++
 include/linux/device.h                        |  2 +
 3 files changed, 70 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index efc7aa7a0670..e83ef4648ea4 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -804,6 +804,15 @@
 			Defaults to the default architecture's huge page size
 			if not specified.

+	deferred_probe_timeout=
+			[KNL] Debugging option to set a timeout in seconds for
+			deferred probe to give up waiting on dependencies to
+			probe. Only specific dependencies (subsystems or
+			drivers) that have opted in will be ignored. A timeout of 0
+			will timeout at the end of initcalls. This option will also
+			dump out devices still on the deferred probe list after
+			retrying.
+
 	dhash_entries=	[KNL]
 			Set number of hash buckets for dentry cache.

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index e85705e84407..fb62f1be40d3 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -55,6 +55,7 @@ static LIST_HEAD(deferred_probe_pending_list);
 static LIST_HEAD(deferred_probe_active_list);
 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
 static struct dentry *deferred_devices;
+static bool initcalls_done;

 /*
  * In some cases, like suspend to RAM or hibernation, It might be reasonable
@@ -219,6 +220,51 @@ static int deferred_devs_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(deferred_devs);

+static int deferred_probe_timeout = -1;
+static int __init deferred_probe_timeout_setup(char *str)
+{
+	deferred_probe_timeout = simple_strtol(str, NULL, 10);
+	return 1;
+}
+__setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
+
+/**
+ * driver_deferred_probe_check_state() - Check deferred probe state
+ * @dev: device to check
+ *
+ * Returns -ENODEV if init is done and all built-in drivers have had a chance
+ * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
+ * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
+ *
+ * Drivers or subsystems can opt-in to calling this function instead of directly
+ * returning -EPROBE_DEFER.
+ */
+int driver_deferred_probe_check_state(struct device *dev)
+{
+	if (initcalls_done) {
+		if (!deferred_probe_timeout) {
+			dev_WARN(dev, "deferred probe timeout, ignoring dependency");
+			return -ETIMEDOUT;
+		}
+		dev_warn(dev, "ignoring dependency for device, assuming no driver");
+		return -ENODEV;
+	}
+	return -EPROBE_DEFER;
+}
+
+static void deferred_probe_timeout_work_func(struct work_struct *work)
+{
+	struct device_private *private, *p;
+
+	deferred_probe_timeout = 0;
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
+		dev_info(private->device, "deferred probe pending");
+}
+static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
@@ -235,6 +281,19 @@ static int deferred_probe_initcall(void)
 	driver_deferred_probe_trigger();
 	/* Sort as many dependencies as possible before exiting initcalls */
 	flush_work(&deferred_probe_work);
+	initcalls_done = true;
+
+	/*
+	 * Trigger deferred probe again, this time we won't defer anything
+	 * that is optional
+	 */
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	if (deferred_probe_timeout > 0) {
+		schedule_delayed_work(&deferred_probe_timeout_work,
+			deferred_probe_timeout * HZ);
+	}
 	return 0;
 }
 late_initcall(deferred_probe_initcall);
diff --git a/include/linux/device.h b/include/linux/device.h
index 575c5a35ece5..d2acc78d279b 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -339,6 +339,8 @@ struct device *driver_find_device(struct device_driver *drv,
 				  struct device *start, void *data,
 				  int (*match)(struct device *dev, void *data));

+int driver_deferred_probe_check_state(struct device *dev);
+
 /**
  * struct subsys_interface - interfaces to device functions
  * @name:       name of the device function
--
2.17.1

[PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Rob Herring]

Deferred probe will currently wait forever on dependent devices to probe,
but sometimes a driver will never exist. It's also not always critical for
a driver to exist. Platforms can rely on default configuration from the
bootloader or reset defaults for things such as pinctrl and power domains.
This is often the case with initial platform support until various drivers
get enabled. There's at least 2 scenarios where deferred probe can render
a platform broken. Both involve using a DT which has more devices and
dependencies than the kernel supports. The 1st case is a driver may be
disabled in the kernel config. The 2nd case is the kernel version may
simply not have the dependent driver. This can happen if using a newer DT
(provided by firmware perhaps) with a stable kernel version. Deferred
probe issues can be difficult to debug especially if the console has
dependencies or userspace fails to boot to a shell.

There are also cases like IOMMUs where only built-in drivers are
supported, so deferring probe after initcalls is not needed. The IOMMU
subsystem implemented its own mechanism to handle this using OF_DECLARE
linker sections.

This commit adds makes ending deferred probe conditional on initcalls
being completed or a debug timeout. Subsystems or drivers may opt-in by
calling driver_deferred_probe_check_init_done() instead of
unconditionally returning -EPROBE_DEFER. They may use additional
information from DT or kernel's config to decide whether to continue to
defer probe or not.

The timeout mechanism is intended for debug purposes and WARNs loudly.
The remaining deferred probe pending list will also be dumped after the
timeout. Not that this timeout won't work for the console which needs
to be enabled before userspace starts. However, if the console's
dependencies are resolved, then the kernel log will be printed (as
opposed to no output).

Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
- Rebase on driver-core-next
- Only allow base 10 for timeout

v3:
- Merged with timeout patch.
- Clarify that deferred_probe_timeout is a debug option.
- Drop the 'optional' param. The only user was pinctrl, so it has to handle
  that functionality.
- Rename function to driver_deferred_probe_check_state
- Added kerneldoc for driver_deferred_probe_check_state
- Print a 1 line warning if stopping deferred probe after initcalls and a
  WARN on timeout.

 .../admin-guide/kernel-parameters.txt         |  9 +++
 drivers/base/dd.c                             | 59 +++++++++++++++++++
 include/linux/device.h                        |  2 +
 3 files changed, 70 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index efc7aa7a0670..e83ef4648ea4 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -804,6 +804,15 @@
 			Defaults to the default architecture's huge page size
 			if not specified.

+	deferred_probe_timeout=
+			[KNL] Debugging option to set a timeout in seconds for
+			deferred probe to give up waiting on dependencies to
+			probe. Only specific dependencies (subsystems or
+			drivers) that have opted in will be ignored. A timeout of 0
+			will timeout at the end of initcalls. This option will also
+			dump out devices still on the deferred probe list after
+			retrying.
+
 	dhash_entries=	[KNL]
 			Set number of hash buckets for dentry cache.

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index e85705e84407..fb62f1be40d3 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -55,6 +55,7 @@ static LIST_HEAD(deferred_probe_pending_list);
 static LIST_HEAD(deferred_probe_active_list);
 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
 static struct dentry *deferred_devices;
+static bool initcalls_done;

 /*
  * In some cases, like suspend to RAM or hibernation, It might be reasonable
@@ -219,6 +220,51 @@ static int deferred_devs_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(deferred_devs);

+static int deferred_probe_timeout = -1;
+static int __init deferred_probe_timeout_setup(char *str)
+{
+	deferred_probe_timeout = simple_strtol(str, NULL, 10);
+	return 1;
+}
+__setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
+
+/**
+ * driver_deferred_probe_check_state() - Check deferred probe state
+ * @dev: device to check
+ *
+ * Returns -ENODEV if init is done and all built-in drivers have had a chance
+ * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
+ * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
+ *
+ * Drivers or subsystems can opt-in to calling this function instead of directly
+ * returning -EPROBE_DEFER.
+ */
+int driver_deferred_probe_check_state(struct device *dev)
+{
+	if (initcalls_done) {
+		if (!deferred_probe_timeout) {
+			dev_WARN(dev, "deferred probe timeout, ignoring dependency");
+			return -ETIMEDOUT;
+		}
+		dev_warn(dev, "ignoring dependency for device, assuming no driver");
+		return -ENODEV;
+	}
+	return -EPROBE_DEFER;
+}
+
+static void deferred_probe_timeout_work_func(struct work_struct *work)
+{
+	struct device_private *private, *p;
+
+	deferred_probe_timeout = 0;
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
+		dev_info(private->device, "deferred probe pending");
+}
+static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
@@ -235,6 +281,19 @@ static int deferred_probe_initcall(void)
 	driver_deferred_probe_trigger();
 	/* Sort as many dependencies as possible before exiting initcalls */
 	flush_work(&deferred_probe_work);
+	initcalls_done = true;
+
+	/*
+	 * Trigger deferred probe again, this time we won't defer anything
+	 * that is optional
+	 */
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	if (deferred_probe_timeout > 0) {
+		schedule_delayed_work(&deferred_probe_timeout_work,
+			deferred_probe_timeout * HZ);
+	}
 	return 0;
 }
 late_initcall(deferred_probe_initcall);
diff --git a/include/linux/device.h b/include/linux/device.h
index 575c5a35ece5..d2acc78d279b 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -339,6 +339,8 @@ struct device *driver_find_device(struct device_driver *drv,
 				  struct device *start, void *data,
 				  int (*match)(struct device *dev, void *data));

+int driver_deferred_probe_check_state(struct device *dev);
+
 /**
  * struct subsys_interface - interfaces to device functions
  * @name:       name of the device function
--
2.17.1

[PATCH v4 2/6] dt-bindings: pinctrl: add a 'pinctrl-use-default' property

[Rob Herring]

Pin setup may be optional in some cases such as the reset default works
or the pin setup is done by the bootloader. In these cases, it is optional
for the OS to support managing the pin controller and pin setup. In order
to support this scenario, add a property 'pinctrl-use-default' to indicate
that the pin configuration is optional.

Signed-off-by: Rob Herring <robh@kernel.org>
---
 .../devicetree/bindings/pinctrl/pinctrl-bindings.txt        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
index ad9bbbba36e9..cef2b5855d60 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
@@ -103,6 +103,12 @@ Optional properties:
 #pinctrl-cells:	Number of pin control cells in addition to the index within the
 		pin controller device instance
 
+pinctrl-use-default: Boolean. Indicates that the OS can use the boot default
+		pin configuration. This allows using an OS that does not have a
+		driver for the pin controller. This property can be set either
+		globally for the pin controller or in child nodes for individual
+		pin group control.
+
 Pin controller devices should contain the pin configuration nodes that client
 devices reference.
 
-- 
2.17.1

[PATCH v4 2/6] dt-bindings: pinctrl: add a 'pinctrl-use-default' property

[Rob Herring]

Pin setup may be optional in some cases such as the reset default works
or the pin setup is done by the bootloader. In these cases, it is optional
for the OS to support managing the pin controller and pin setup. In order
to support this scenario, add a property 'pinctrl-use-default' to indicate
that the pin configuration is optional.

Signed-off-by: Rob Herring <robh@kernel.org>
---
 .../devicetree/bindings/pinctrl/pinctrl-bindings.txt        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
index ad9bbbba36e9..cef2b5855d60 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
@@ -103,6 +103,12 @@ Optional properties:
 #pinctrl-cells:	Number of pin control cells in addition to the index within the
 		pin controller device instance
 
+pinctrl-use-default: Boolean. Indicates that the OS can use the boot default
+		pin configuration. This allows using an OS that does not have a
+		driver for the pin controller. This property can be set either
+		globally for the pin controller or in child nodes for individual
+		pin group control.
+
 Pin controller devices should contain the pin configuration nodes that client
 devices reference.
 
-- 
2.17.1

_______________________________________________
boot-architecture mailing list
boot-architecture@lists.linaro.org
https://lists.linaro.org/mailman/listinfo/boot-architecture

[PATCH v4 2/6] dt-bindings: pinctrl: add a 'pinctrl-use-default' property

[Rob Herring]

Pin setup may be optional in some cases such as the reset default works
or the pin setup is done by the bootloader. In these cases, it is optional
for the OS to support managing the pin controller and pin setup. In order
to support this scenario, add a property 'pinctrl-use-default' to indicate
that the pin configuration is optional.

Signed-off-by: Rob Herring <robh@kernel.org>
---
 .../devicetree/bindings/pinctrl/pinctrl-bindings.txt        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
index ad9bbbba36e9..cef2b5855d60 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
@@ -103,6 +103,12 @@ Optional properties:
 #pinctrl-cells:	Number of pin control cells in addition to the index within the
 		pin controller device instance
 
+pinctrl-use-default: Boolean. Indicates that the OS can use the boot default
+		pin configuration. This allows using an OS that does not have a
+		driver for the pin controller. This property can be set either
+		globally for the pin controller or in child nodes for individual
+		pin group control.
+
 Pin controller devices should contain the pin configuration nodes that client
 devices reference.
 
-- 
2.17.1

[PATCH v4 3/6] pinctrl: Support stopping deferred probe after initcalls

[Rob Herring]

Pinctrl drivers are a common dependency which can prevent a system
booting even if the default or bootloader configured settings can work.
If a pinctrl node in DT indicates that the default pin setup can be used
with the 'pinctrl-use-default' property, then only defer probe until
initcalls are done. If the deferred probe timeout is enabled or loadable
modules are disabled, then we'll stop deferring probe regardless of the
DT property. This gives platforms the option to work without their
pinctrl driver being enabled.

Dropped the pinctrl specific deferring probe message as the driver core
can print deferred probe related messages if needed.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
- Add Linus' R-by.

v3:
- Drop pinctrl deferred probe msg in favor of driver core messages
- Move the handling of "pinctrl-use-default" option out of driver core
- Stop deferring probe if modules are not enabled.

 drivers/pinctrl/devicetree.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
index c4aa411f5935..2969ff3162c3 100644
--- a/drivers/pinctrl/devicetree.c
+++ b/drivers/pinctrl/devicetree.c
@@ -111,17 +111,24 @@ static int dt_to_map_one_config(struct pinctrl *p,
 	int ret;
 	struct pinctrl_map *map;
 	unsigned num_maps;
+	bool allow_default = false;

 	/* Find the pin controller containing np_config */
 	np_pctldev = of_node_get(np_config);
 	for (;;) {
+		if (!allow_default)
+			allow_default = of_property_read_bool(np_pctldev,
+							      "pinctrl-use-default");
+
 		np_pctldev = of_get_next_parent(np_pctldev);
 		if (!np_pctldev || of_node_is_root(np_pctldev)) {
-			dev_info(p->dev, "could not find pctldev for node %pOF, deferring probe\n",
-				np_config);
 			of_node_put(np_pctldev);
-			/* OK let's just assume this will appear later then */
-			return -EPROBE_DEFER;
+			ret = driver_deferred_probe_check_state(p->dev);
+			/* keep deferring if modules are enabled unless we've timed out */
+			if (IS_ENABLED(CONFIG_MODULES) && !allow_default && ret == -ENODEV)
+				ret = -EPROBE_DEFER;
+
+			return ret;
 		}
 		/* If we're creating a hog we can use the passed pctldev */
 		if (hog_pctldev && (np_pctldev == p->dev->of_node)) {
--
2.17.1

[PATCH v4 3/6] pinctrl: Support stopping deferred probe after initcalls

[Rob Herring]

Pinctrl drivers are a common dependency which can prevent a system
booting even if the default or bootloader configured settings can work.
If a pinctrl node in DT indicates that the default pin setup can be used
with the 'pinctrl-use-default' property, then only defer probe until
initcalls are done. If the deferred probe timeout is enabled or loadable
modules are disabled, then we'll stop deferring probe regardless of the
DT property. This gives platforms the option to work without their
pinctrl driver being enabled.

Dropped the pinctrl specific deferring probe message as the driver core
can print deferred probe related messages if needed.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
- Add Linus' R-by.

v3:
- Drop pinctrl deferred probe msg in favor of driver core messages
- Move the handling of "pinctrl-use-default" option out of driver core
- Stop deferring probe if modules are not enabled.

 drivers/pinctrl/devicetree.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
index c4aa411f5935..2969ff3162c3 100644
--- a/drivers/pinctrl/devicetree.c
+++ b/drivers/pinctrl/devicetree.c
@@ -111,17 +111,24 @@ static int dt_to_map_one_config(struct pinctrl *p,
 	int ret;
 	struct pinctrl_map *map;
 	unsigned num_maps;
+	bool allow_default = false;

 	/* Find the pin controller containing np_config */
 	np_pctldev = of_node_get(np_config);
 	for (;;) {
+		if (!allow_default)
+			allow_default = of_property_read_bool(np_pctldev,
+							      "pinctrl-use-default");
+
 		np_pctldev = of_get_next_parent(np_pctldev);
 		if (!np_pctldev || of_node_is_root(np_pctldev)) {
-			dev_info(p->dev, "could not find pctldev for node %pOF, deferring probe\n",
-				np_config);
 			of_node_put(np_pctldev);
-			/* OK let's just assume this will appear later then */
-			return -EPROBE_DEFER;
+			ret = driver_deferred_probe_check_state(p->dev);
+			/* keep deferring if modules are enabled unless we've timed out */
+			if (IS_ENABLED(CONFIG_MODULES) && !allow_default && ret == -ENODEV)
+				ret = -EPROBE_DEFER;
+
+			return ret;
 		}
 		/* If we're creating a hog we can use the passed pctldev */
 		if (hog_pctldev && (np_pctldev == p->dev->of_node)) {
--
2.17.1

[PATCH v4 4/6] iommu: Stop deferring probe at end of initcalls

[Rob Herring]

The IOMMU subsystem has its own mechanism to not defer probe if driver
support is missing. Now that the driver core supports stopping deferring
probe if drivers aren't built-in (and probed), use the driver core
support so the IOMMU specific support can be removed.

Acked-by: Joerg Roedel <jroedel@suse.de>
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Rob Herring <robh@kernel.org>
---
 drivers/iommu/of_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5c36a8b7656a..78ddf47dd67a 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -133,7 +133,7 @@ static int of_iommu_xlate(struct device *dev,
 	 * a proper probe-ordering dependency mechanism in future.
 	 */
 	if (!ops)
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 
 	return ops->of_xlate(dev, iommu_spec);
 }
-- 
2.17.1

[PATCH v4 4/6] iommu: Stop deferring probe at end of initcalls

[Rob Herring]

The IOMMU subsystem has its own mechanism to not defer probe if driver
support is missing. Now that the driver core supports stopping deferring
probe if drivers aren't built-in (and probed), use the driver core
support so the IOMMU specific support can be removed.

Acked-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Signed-off-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 drivers/iommu/of_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5c36a8b7656a..78ddf47dd67a 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -133,7 +133,7 @@ static int of_iommu_xlate(struct device *dev,
 	 * a proper probe-ordering dependency mechanism in future.
 	 */
 	if (!ops)
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 
 	return ops->of_xlate(dev, iommu_spec);
 }
-- 
2.17.1

[PATCH v4 4/6] iommu: Stop deferring probe at end of initcalls

[Rob Herring]

The IOMMU subsystem has its own mechanism to not defer probe if driver
support is missing. Now that the driver core supports stopping deferring
probe if drivers aren't built-in (and probed), use the driver core
support so the IOMMU specific support can be removed.

Acked-by: Joerg Roedel <jroedel@suse.de>
Cc: iommu at lists.linux-foundation.org
Signed-off-by: Rob Herring <robh@kernel.org>
---
 drivers/iommu/of_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5c36a8b7656a..78ddf47dd67a 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -133,7 +133,7 @@ static int of_iommu_xlate(struct device *dev,
 	 * a proper probe-ordering dependency mechanism in future.
 	 */
 	if (!ops)
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 
 	return ops->of_xlate(dev, iommu_spec);
 }
-- 
2.17.1

[PATCH v4 5/6] iommu: Remove IOMMU_OF_DECLARE

[Rob Herring]

Now that we use the driver core to stop deferred probe for missing
drivers, IOMMU_OF_DECLARE can be removed.

This is slightly less optimal than having a list of built-in drivers in
that we'll now defer probe twice before giving up. This shouldn't have a
significant impact on boot times as past discussions about deferred
probe have given no evidence of deferred probe having a substantial
impact.

Cc: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Cc: Kukjin Kim <kgene-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Krzysztof Kozlowski <krzk-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Rob Clark <robdclark-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
Cc: Frank Rowand <frowand.list-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Cc: linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Acked-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Acked-by: Marek Szyprowski <m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Acked-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Signed-off-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 drivers/iommu/arm-smmu-v3.c       |  2 --
 drivers/iommu/arm-smmu.c          |  7 -------
 drivers/iommu/exynos-iommu.c      |  2 --
 drivers/iommu/ipmmu-vmsa.c        |  3 ---
 drivers/iommu/msm_iommu.c         |  2 --
 drivers/iommu/of_iommu.c          | 19 +------------------
 drivers/iommu/qcom_iommu.c        |  2 --
 drivers/iommu/rockchip-iommu.c    |  2 --
 include/asm-generic/vmlinux.lds.h |  2 --
 include/linux/of_iommu.h          |  4 ----
 10 files changed, 1 insertion(+), 44 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 1d647104bccc..22bdabd3d8e0 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2915,8 +2915,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv3, "arm,smmu-v3");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index f7a96bcf94a6..c73cfce1ccc0 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2211,13 +2211,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv1, "arm,smmu-v1");
-IOMMU_OF_DECLARE(arm_smmuv2, "arm,smmu-v2");
-IOMMU_OF_DECLARE(arm_mmu400, "arm,mmu-400");
-IOMMU_OF_DECLARE(arm_mmu401, "arm,mmu-401");
-IOMMU_OF_DECLARE(arm_mmu500, "arm,mmu-500");
-IOMMU_OF_DECLARE(cavium_smmuv2, "cavium,smmu-v2");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 85879cfec52f..b128cb4372d3 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -1390,5 +1390,3 @@ static int __init exynos_iommu_init(void)
 	return ret;
 }
 core_initcall(exynos_iommu_init);
-
-IOMMU_OF_DECLARE(exynos_iommu_of, "samsung,exynos-sysmmu");
diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index 40ae6e87cb88..f026aa16d5f1 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -1108,9 +1108,6 @@ static void __exit ipmmu_exit(void)
 subsys_initcall(ipmmu_init);
 module_exit(ipmmu_exit);
 
-IOMMU_OF_DECLARE(ipmmu_vmsa_iommu_of, "renesas,ipmmu-vmsa");
-IOMMU_OF_DECLARE(ipmmu_r8a7795_iommu_of, "renesas,ipmmu-r8a7795");
-
 MODULE_DESCRIPTION("IOMMU API for Renesas VMSA-compatible IPMMU");
 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 0d3350463a3f..27377742600d 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -877,7 +877,5 @@ static void __exit msm_iommu_driver_exit(void)
 subsys_initcall(msm_iommu_driver_init);
 module_exit(msm_iommu_driver_exit);
 
-IOMMU_OF_DECLARE(msm_iommu_of, "qcom,apq8064-iommu");
-
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Stepan Moskovchenko <stepanm-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>");
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 78ddf47dd67a..f7787e757244 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -27,9 +27,6 @@
 
 #define NO_IOMMU	1
 
-static const struct of_device_id __iommu_of_table_sentinel
-	__used __section(__iommu_of_table_end);
-
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
  *
@@ -98,19 +95,6 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
-static bool of_iommu_driver_present(struct device_node *np)
-{
-	/*
-	 * If the IOMMU still isn't ready by the time we reach init, assume
-	 * it never will be. We don't want to defer indefinitely, nor attempt
-	 * to dereference __iommu_of_table after it's been freed.
-	 */
-	if (system_state >= SYSTEM_RUNNING)
-		return false;
-
-	return of_match_node(&__iommu_of_table, np);
-}
-
 static int of_iommu_xlate(struct device *dev,
 			  struct of_phandle_args *iommu_spec)
 {
@@ -120,8 +104,7 @@ static int of_iommu_xlate(struct device *dev,
 
 	ops = iommu_ops_from_fwnode(fwnode);
 	if ((ops && !ops->of_xlate) ||
-	    !of_device_is_available(iommu_spec->np) ||
-	    (!ops && !of_iommu_driver_present(iommu_spec->np)))
+	    !of_device_is_available(iommu_spec->np))
 		return NO_IOMMU;
 
 	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index fe88a4880d3a..b48aee82d14b 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -945,7 +945,5 @@ static void __exit qcom_iommu_exit(void)
 module_init(qcom_iommu_init);
 module_exit(qcom_iommu_exit);
 
-IOMMU_OF_DECLARE(qcom_iommu_dev, "qcom,msm-iommu-v1");
-
 MODULE_DESCRIPTION("IOMMU API for QCOM IOMMU v1 implementations");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 054cd2c8e9c8..de8d3bf91b23 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1284,8 +1284,6 @@ static int __init rk_iommu_init(void)
 }
 subsys_initcall(rk_iommu_init);
 
-IOMMU_OF_DECLARE(rk_iommu_of, "rockchip,iommu");
-
 MODULE_DESCRIPTION("IOMMU API for Rockchip");
 MODULE_AUTHOR("Simon Xue <xxm-TNX95d0MmH7DzftRWevZcw@public.gmane.org> and Daniel Kurtz <djkurtz-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>");
 MODULE_ALIAS("platform:rockchip-iommu");
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e373e2e10f6a..f173b5f30dbe 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -218,7 +218,6 @@
 #define TIMER_OF_TABLES()	OF_TABLE(CONFIG_TIMER_OF, timer)
 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
 #define CLK_OF_TABLES()		OF_TABLE(CONFIG_COMMON_CLK, clk)
-#define IOMMU_OF_TABLES()	OF_TABLE(CONFIG_OF_IOMMU, iommu)
 #define RESERVEDMEM_OF_TABLES()	OF_TABLE(CONFIG_OF_RESERVED_MEM, reservedmem)
 #define CPU_METHOD_OF_TABLES()	OF_TABLE(CONFIG_SMP, cpu_method)
 #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
@@ -601,7 +600,6 @@
 	CLK_OF_TABLES()							\
 	RESERVEDMEM_OF_TABLES()						\
 	TIMER_OF_TABLES()						\
-	IOMMU_OF_TABLES()						\
 	CPU_METHOD_OF_TABLES()						\
 	CPUIDLE_METHOD_OF_TABLES()					\
 	KERNEL_DTB()							\
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 4fa654e4b5a9..f3d40dd7bb66 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -32,8 +32,4 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
 
 #endif	/* CONFIG_OF_IOMMU */
 
-extern struct of_device_id __iommu_of_table;
-
-#define IOMMU_OF_DECLARE(name, compat)	OF_DECLARE_1(iommu, name, compat, NULL)
-
 #endif /* __OF_IOMMU_H */
-- 
2.17.1

[PATCH v4 5/6] iommu: Remove IOMMU_OF_DECLARE

[Rob Herring]

Now that we use the driver core to stop deferred probe for missing
drivers, IOMMU_OF_DECLARE can be removed.

This is slightly less optimal than having a list of built-in drivers in
that we'll now defer probe twice before giving up. This shouldn't have a
significant impact on boot times as past discussions about deferred
probe have given no evidence of deferred probe having a substantial
impact.

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-rockchip@lists.infradead.org
Cc: devicetree@vger.kernel.org
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
---
 drivers/iommu/arm-smmu-v3.c       |  2 --
 drivers/iommu/arm-smmu.c          |  7 -------
 drivers/iommu/exynos-iommu.c      |  2 --
 drivers/iommu/ipmmu-vmsa.c        |  3 ---
 drivers/iommu/msm_iommu.c         |  2 --
 drivers/iommu/of_iommu.c          | 19 +------------------
 drivers/iommu/qcom_iommu.c        |  2 --
 drivers/iommu/rockchip-iommu.c    |  2 --
 include/asm-generic/vmlinux.lds.h |  2 --
 include/linux/of_iommu.h          |  4 ----
 10 files changed, 1 insertion(+), 44 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 1d647104bccc..22bdabd3d8e0 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2915,8 +2915,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv3, "arm,smmu-v3");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index f7a96bcf94a6..c73cfce1ccc0 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2211,13 +2211,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv1, "arm,smmu-v1");
-IOMMU_OF_DECLARE(arm_smmuv2, "arm,smmu-v2");
-IOMMU_OF_DECLARE(arm_mmu400, "arm,mmu-400");
-IOMMU_OF_DECLARE(arm_mmu401, "arm,mmu-401");
-IOMMU_OF_DECLARE(arm_mmu500, "arm,mmu-500");
-IOMMU_OF_DECLARE(cavium_smmuv2, "cavium,smmu-v2");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 85879cfec52f..b128cb4372d3 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -1390,5 +1390,3 @@ static int __init exynos_iommu_init(void)
 	return ret;
 }
 core_initcall(exynos_iommu_init);
-
-IOMMU_OF_DECLARE(exynos_iommu_of, "samsung,exynos-sysmmu");
diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index 40ae6e87cb88..f026aa16d5f1 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -1108,9 +1108,6 @@ static void __exit ipmmu_exit(void)
 subsys_initcall(ipmmu_init);
 module_exit(ipmmu_exit);
 
-IOMMU_OF_DECLARE(ipmmu_vmsa_iommu_of, "renesas,ipmmu-vmsa");
-IOMMU_OF_DECLARE(ipmmu_r8a7795_iommu_of, "renesas,ipmmu-r8a7795");
-
 MODULE_DESCRIPTION("IOMMU API for Renesas VMSA-compatible IPMMU");
 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 0d3350463a3f..27377742600d 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -877,7 +877,5 @@ static void __exit msm_iommu_driver_exit(void)
 subsys_initcall(msm_iommu_driver_init);
 module_exit(msm_iommu_driver_exit);
 
-IOMMU_OF_DECLARE(msm_iommu_of, "qcom,apq8064-iommu");
-
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Stepan Moskovchenko <stepanm@codeaurora.org>");
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 78ddf47dd67a..f7787e757244 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -27,9 +27,6 @@
 
 #define NO_IOMMU	1
 
-static const struct of_device_id __iommu_of_table_sentinel
-	__used __section(__iommu_of_table_end);
-
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
  *
@@ -98,19 +95,6 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
-static bool of_iommu_driver_present(struct device_node *np)
-{
-	/*
-	 * If the IOMMU still isn't ready by the time we reach init, assume
-	 * it never will be. We don't want to defer indefinitely, nor attempt
-	 * to dereference __iommu_of_table after it's been freed.
-	 */
-	if (system_state >= SYSTEM_RUNNING)
-		return false;
-
-	return of_match_node(&__iommu_of_table, np);
-}
-
 static int of_iommu_xlate(struct device *dev,
 			  struct of_phandle_args *iommu_spec)
 {
@@ -120,8 +104,7 @@ static int of_iommu_xlate(struct device *dev,
 
 	ops = iommu_ops_from_fwnode(fwnode);
 	if ((ops && !ops->of_xlate) ||
-	    !of_device_is_available(iommu_spec->np) ||
-	    (!ops && !of_iommu_driver_present(iommu_spec->np)))
+	    !of_device_is_available(iommu_spec->np))
 		return NO_IOMMU;
 
 	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index fe88a4880d3a..b48aee82d14b 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -945,7 +945,5 @@ static void __exit qcom_iommu_exit(void)
 module_init(qcom_iommu_init);
 module_exit(qcom_iommu_exit);
 
-IOMMU_OF_DECLARE(qcom_iommu_dev, "qcom,msm-iommu-v1");
-
 MODULE_DESCRIPTION("IOMMU API for QCOM IOMMU v1 implementations");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 054cd2c8e9c8..de8d3bf91b23 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1284,8 +1284,6 @@ static int __init rk_iommu_init(void)
 }
 subsys_initcall(rk_iommu_init);
 
-IOMMU_OF_DECLARE(rk_iommu_of, "rockchip,iommu");
-
 MODULE_DESCRIPTION("IOMMU API for Rockchip");
 MODULE_AUTHOR("Simon Xue <xxm@rock-chips.com> and Daniel Kurtz <djkurtz@chromium.org>");
 MODULE_ALIAS("platform:rockchip-iommu");
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e373e2e10f6a..f173b5f30dbe 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -218,7 +218,6 @@
 #define TIMER_OF_TABLES()	OF_TABLE(CONFIG_TIMER_OF, timer)
 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
 #define CLK_OF_TABLES()		OF_TABLE(CONFIG_COMMON_CLK, clk)
-#define IOMMU_OF_TABLES()	OF_TABLE(CONFIG_OF_IOMMU, iommu)
 #define RESERVEDMEM_OF_TABLES()	OF_TABLE(CONFIG_OF_RESERVED_MEM, reservedmem)
 #define CPU_METHOD_OF_TABLES()	OF_TABLE(CONFIG_SMP, cpu_method)
 #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
@@ -601,7 +600,6 @@
 	CLK_OF_TABLES()							\
 	RESERVEDMEM_OF_TABLES()						\
 	TIMER_OF_TABLES()						\
-	IOMMU_OF_TABLES()						\
 	CPU_METHOD_OF_TABLES()						\
 	CPUIDLE_METHOD_OF_TABLES()					\
 	KERNEL_DTB()							\
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 4fa654e4b5a9..f3d40dd7bb66 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -32,8 +32,4 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
 
 #endif	/* CONFIG_OF_IOMMU */
 
-extern struct of_device_id __iommu_of_table;
-
-#define IOMMU_OF_DECLARE(name, compat)	OF_DECLARE_1(iommu, name, compat, NULL)
-
 #endif /* __OF_IOMMU_H */
-- 
2.17.1

[PATCH v4 5/6] iommu: Remove IOMMU_OF_DECLARE

[Rob Herring]

Now that we use the driver core to stop deferred probe for missing
drivers, IOMMU_OF_DECLARE can be removed.

This is slightly less optimal than having a list of built-in drivers in
that we'll now defer probe twice before giving up. This shouldn't have a
significant impact on boot times as past discussions about deferred
probe have given no evidence of deferred probe having a substantial
impact.

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: iommu at lists.linux-foundation.org
Cc: linux-samsung-soc at vger.kernel.org
Cc: linux-arm-msm at vger.kernel.org
Cc: linux-rockchip at lists.infradead.org
Cc: devicetree at vger.kernel.org
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
---
 drivers/iommu/arm-smmu-v3.c       |  2 --
 drivers/iommu/arm-smmu.c          |  7 -------
 drivers/iommu/exynos-iommu.c      |  2 --
 drivers/iommu/ipmmu-vmsa.c        |  3 ---
 drivers/iommu/msm_iommu.c         |  2 --
 drivers/iommu/of_iommu.c          | 19 +------------------
 drivers/iommu/qcom_iommu.c        |  2 --
 drivers/iommu/rockchip-iommu.c    |  2 --
 include/asm-generic/vmlinux.lds.h |  2 --
 include/linux/of_iommu.h          |  4 ----
 10 files changed, 1 insertion(+), 44 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 1d647104bccc..22bdabd3d8e0 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2915,8 +2915,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv3, "arm,smmu-v3");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index f7a96bcf94a6..c73cfce1ccc0 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2211,13 +2211,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv1, "arm,smmu-v1");
-IOMMU_OF_DECLARE(arm_smmuv2, "arm,smmu-v2");
-IOMMU_OF_DECLARE(arm_mmu400, "arm,mmu-400");
-IOMMU_OF_DECLARE(arm_mmu401, "arm,mmu-401");
-IOMMU_OF_DECLARE(arm_mmu500, "arm,mmu-500");
-IOMMU_OF_DECLARE(cavium_smmuv2, "cavium,smmu-v2");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 85879cfec52f..b128cb4372d3 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -1390,5 +1390,3 @@ static int __init exynos_iommu_init(void)
 	return ret;
 }
 core_initcall(exynos_iommu_init);
-
-IOMMU_OF_DECLARE(exynos_iommu_of, "samsung,exynos-sysmmu");
diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index 40ae6e87cb88..f026aa16d5f1 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -1108,9 +1108,6 @@ static void __exit ipmmu_exit(void)
 subsys_initcall(ipmmu_init);
 module_exit(ipmmu_exit);
 
-IOMMU_OF_DECLARE(ipmmu_vmsa_iommu_of, "renesas,ipmmu-vmsa");
-IOMMU_OF_DECLARE(ipmmu_r8a7795_iommu_of, "renesas,ipmmu-r8a7795");
-
 MODULE_DESCRIPTION("IOMMU API for Renesas VMSA-compatible IPMMU");
 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 0d3350463a3f..27377742600d 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -877,7 +877,5 @@ static void __exit msm_iommu_driver_exit(void)
 subsys_initcall(msm_iommu_driver_init);
 module_exit(msm_iommu_driver_exit);
 
-IOMMU_OF_DECLARE(msm_iommu_of, "qcom,apq8064-iommu");
-
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Stepan Moskovchenko <stepanm@codeaurora.org>");
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 78ddf47dd67a..f7787e757244 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -27,9 +27,6 @@
 
 #define NO_IOMMU	1
 
-static const struct of_device_id __iommu_of_table_sentinel
-	__used __section(__iommu_of_table_end);
-
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
  *
@@ -98,19 +95,6 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
-static bool of_iommu_driver_present(struct device_node *np)
-{
-	/*
-	 * If the IOMMU still isn't ready by the time we reach init, assume
-	 * it never will be. We don't want to defer indefinitely, nor attempt
-	 * to dereference __iommu_of_table after it's been freed.
-	 */
-	if (system_state >= SYSTEM_RUNNING)
-		return false;
-
-	return of_match_node(&__iommu_of_table, np);
-}
-
 static int of_iommu_xlate(struct device *dev,
 			  struct of_phandle_args *iommu_spec)
 {
@@ -120,8 +104,7 @@ static int of_iommu_xlate(struct device *dev,
 
 	ops = iommu_ops_from_fwnode(fwnode);
 	if ((ops && !ops->of_xlate) ||
-	    !of_device_is_available(iommu_spec->np) ||
-	    (!ops && !of_iommu_driver_present(iommu_spec->np)))
+	    !of_device_is_available(iommu_spec->np))
 		return NO_IOMMU;
 
 	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index fe88a4880d3a..b48aee82d14b 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -945,7 +945,5 @@ static void __exit qcom_iommu_exit(void)
 module_init(qcom_iommu_init);
 module_exit(qcom_iommu_exit);
 
-IOMMU_OF_DECLARE(qcom_iommu_dev, "qcom,msm-iommu-v1");
-
 MODULE_DESCRIPTION("IOMMU API for QCOM IOMMU v1 implementations");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 054cd2c8e9c8..de8d3bf91b23 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1284,8 +1284,6 @@ static int __init rk_iommu_init(void)
 }
 subsys_initcall(rk_iommu_init);
 
-IOMMU_OF_DECLARE(rk_iommu_of, "rockchip,iommu");
-
 MODULE_DESCRIPTION("IOMMU API for Rockchip");
 MODULE_AUTHOR("Simon Xue <xxm@rock-chips.com> and Daniel Kurtz <djkurtz@chromium.org>");
 MODULE_ALIAS("platform:rockchip-iommu");
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e373e2e10f6a..f173b5f30dbe 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -218,7 +218,6 @@
 #define TIMER_OF_TABLES()	OF_TABLE(CONFIG_TIMER_OF, timer)
 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
 #define CLK_OF_TABLES()		OF_TABLE(CONFIG_COMMON_CLK, clk)
-#define IOMMU_OF_TABLES()	OF_TABLE(CONFIG_OF_IOMMU, iommu)
 #define RESERVEDMEM_OF_TABLES()	OF_TABLE(CONFIG_OF_RESERVED_MEM, reservedmem)
 #define CPU_METHOD_OF_TABLES()	OF_TABLE(CONFIG_SMP, cpu_method)
 #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
@@ -601,7 +600,6 @@
 	CLK_OF_TABLES()							\
 	RESERVEDMEM_OF_TABLES()						\
 	TIMER_OF_TABLES()						\
-	IOMMU_OF_TABLES()						\
 	CPU_METHOD_OF_TABLES()						\
 	CPUIDLE_METHOD_OF_TABLES()					\
 	KERNEL_DTB()							\
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 4fa654e4b5a9..f3d40dd7bb66 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -32,8 +32,4 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
 
 #endif	/* CONFIG_OF_IOMMU */
 
-extern struct of_device_id __iommu_of_table;
-
-#define IOMMU_OF_DECLARE(name, compat)	OF_DECLARE_1(iommu, name, compat, NULL)
-
 #endif /* __OF_IOMMU_H */
-- 
2.17.1

[PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Rob Herring]

All PM domain drivers must be built-in (at least those using DT), so
there is no point deferring probe after initcalls are done. Continuing
to defer probe may prevent booting successfully even if managing PM
domains is not required. This can happen if the user failed to enable
the driver or if power-domains are added to a platform's DT, but there
is not yet a driver (e.g. a new DTB with an old kernel).

Call the driver core function driver_deferred_probe_check_init_done()
instead of just returning -EPROBE_DEFER to stop deferring probe when
initcalls are done.

Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
 - Add Rafael's ack

v3:
  - Update to new function name

 drivers/base/power/domain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4925af5c4cf0..8c12213875c6 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
 		mutex_unlock(&gpd_list_lock);
 		dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
 			__func__, PTR_ERR(pd));
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 	}

 	dev_dbg(dev, "adding to PM domain %s\n", pd->name);
--
2.17.1

[PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Rob Herring]

All PM domain drivers must be built-in (at least those using DT), so
there is no point deferring probe after initcalls are done. Continuing
to defer probe may prevent booting successfully even if managing PM
domains is not required. This can happen if the user failed to enable
the driver or if power-domains are added to a platform's DT, but there
is not yet a driver (e.g. a new DTB with an old kernel).

Call the driver core function driver_deferred_probe_check_init_done()
instead of just returning -EPROBE_DEFER to stop deferring probe when
initcalls are done.

Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-pm at vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
---
v4:
 - Add Rafael's ack

v3:
  - Update to new function name

 drivers/base/power/domain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4925af5c4cf0..8c12213875c6 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
 		mutex_unlock(&gpd_list_lock);
 		dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
 			__func__, PTR_ERR(pd));
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 	}

 	dev_dbg(dev, "adding to PM domain %s\n", pd->name);
--
2.17.1

Re: [PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Russell King - ARM Linux]

On Mon, Jul 09, 2018 at 09:41:48AM -0600, Rob Herring wrote:
> Deferred probe will currently wait forever on dependent devices to probe,
> but sometimes a driver will never exist. It's also not always critical for
> a driver to exist. Platforms can rely on default configuration from the
> bootloader or reset defaults for things such as pinctrl and power domains.
> This is often the case with initial platform support until various drivers
> get enabled. There's at least 2 scenarios where deferred probe can render
> a platform broken. Both involve using a DT which has more devices and
> dependencies than the kernel supports. The 1st case is a driver may be
> disabled in the kernel config. The 2nd case is the kernel version may
> simply not have the dependent driver. This can happen if using a newer DT
> (provided by firmware perhaps) with a stable kernel version. Deferred
> probe issues can be difficult to debug especially if the console has
> dependencies or userspace fails to boot to a shell.
> 
> There are also cases like IOMMUs where only built-in drivers are
> supported, so deferring probe after initcalls is not needed. The IOMMU
> subsystem implemented its own mechanism to handle this using OF_DECLARE
> linker sections.
> 
> This commit adds makes ending deferred probe conditional on initcalls
> being completed or a debug timeout. Subsystems or drivers may opt-in by
> calling driver_deferred_probe_check_init_done() instead of
> unconditionally returning -EPROBE_DEFER. They may use additional
> information from DT or kernel's config to decide whether to continue to
> defer probe or not.
> 
> The timeout mechanism is intended for debug purposes and WARNs loudly.
> The remaining deferred probe pending list will also be dumped after the
> timeout. Not that this timeout won't work for the console which needs
> to be enabled before userspace starts. However, if the console's
> dependencies are resolved, then the kernel log will be printed (as
> opposed to no output).

So what happens if we have a set of modules which use deferred probing
in order to work?

For example, with sound stuff built as modules, and auto-loaded in
parallel by udev, the modules get added in a random order.  The
modules have non-udev obvious dependencies between them (resource
dependencies) which result in deferred probing being necessary to
bring the device up.

Eg,

snd_soc_kirkwood_spdif module declares the ASoC card.
snd_soc_spdif_tx is a codec as a loadable module.
snd_soc_kirkwood is the CPU digital audio interface module.

What I commonly see is this module load order:

snd_soc_kirkwood_spdif, then snd_soc_kirkwood and then snd_soc_spdif_tx.

This results at boot in:

kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CODEC DAI dit-hifi not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CODEC DAI dit-hifi not registered
kirkwood-spdif-audio audio-subsystem: snd-soc-dummy-dai <-> kirkwood-fe mapping ok
kirkwood-spdif-audio audio-subsystem: multicodec <-> kirkwood-spdif mapping ok

at boot, where most of these are deferred probe attempts.

So, disabling deferred probing after all the kernel-internal initcalls
are run is wrong.  You can have deferred probing required due to
external modules, and this can kick in at any time (think about
hot-pluggable hardware with a driver that's somehow componentised,
like an audio device...)

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

[PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Russell King - ARM Linux]

On Mon, Jul 09, 2018 at 09:41:48AM -0600, Rob Herring wrote:
> Deferred probe will currently wait forever on dependent devices to probe,
> but sometimes a driver will never exist. It's also not always critical for
> a driver to exist. Platforms can rely on default configuration from the
> bootloader or reset defaults for things such as pinctrl and power domains.
> This is often the case with initial platform support until various drivers
> get enabled. There's at least 2 scenarios where deferred probe can render
> a platform broken. Both involve using a DT which has more devices and
> dependencies than the kernel supports. The 1st case is a driver may be
> disabled in the kernel config. The 2nd case is the kernel version may
> simply not have the dependent driver. This can happen if using a newer DT
> (provided by firmware perhaps) with a stable kernel version. Deferred
> probe issues can be difficult to debug especially if the console has
> dependencies or userspace fails to boot to a shell.
> 
> There are also cases like IOMMUs where only built-in drivers are
> supported, so deferring probe after initcalls is not needed. The IOMMU
> subsystem implemented its own mechanism to handle this using OF_DECLARE
> linker sections.
> 
> This commit adds makes ending deferred probe conditional on initcalls
> being completed or a debug timeout. Subsystems or drivers may opt-in by
> calling driver_deferred_probe_check_init_done() instead of
> unconditionally returning -EPROBE_DEFER. They may use additional
> information from DT or kernel's config to decide whether to continue to
> defer probe or not.
> 
> The timeout mechanism is intended for debug purposes and WARNs loudly.
> The remaining deferred probe pending list will also be dumped after the
> timeout. Not that this timeout won't work for the console which needs
> to be enabled before userspace starts. However, if the console's
> dependencies are resolved, then the kernel log will be printed (as
> opposed to no output).

So what happens if we have a set of modules which use deferred probing
in order to work?

For example, with sound stuff built as modules, and auto-loaded in
parallel by udev, the modules get added in a random order.  The
modules have non-udev obvious dependencies between them (resource
dependencies) which result in deferred probing being necessary to
bring the device up.

Eg,

snd_soc_kirkwood_spdif module declares the ASoC card.
snd_soc_spdif_tx is a codec as a loadable module.
snd_soc_kirkwood is the CPU digital audio interface module.

What I commonly see is this module load order:

snd_soc_kirkwood_spdif, then snd_soc_kirkwood and then snd_soc_spdif_tx.

This results at boot in:

kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CPU DAI kirkwood-fe not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CODEC DAI dit-hifi not registered
kirkwood-spdif-audio audio-subsystem: ASoC: CODEC DAI dit-hifi not registered
kirkwood-spdif-audio audio-subsystem: snd-soc-dummy-dai <-> kirkwood-fe mapping ok
kirkwood-spdif-audio audio-subsystem: multicodec <-> kirkwood-spdif mapping ok

at boot, where most of these are deferred probe attempts.

So, disabling deferred probing after all the kernel-internal initcalls
are run is wrong.  You can have deferred probing required due to
external modules, and this can kick in at any time (think about
hot-pluggable hardware with a driver that's somehow componentised,
like an audio device...)

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

Re: [PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Rob Herring]

On Mon, Jul 9, 2018 at 9:52 AM Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
>
> On Mon, Jul 09, 2018 at 09:41:48AM -0600, Rob Herring wrote:
> > Deferred probe will currently wait forever on dependent devices to probe,
> > but sometimes a driver will never exist. It's also not always critical for
> > a driver to exist. Platforms can rely on default configuration from the
> > bootloader or reset defaults for things such as pinctrl and power domains.
> > This is often the case with initial platform support until various drivers
> > get enabled. There's at least 2 scenarios where deferred probe can render
> > a platform broken. Both involve using a DT which has more devices and
> > dependencies than the kernel supports. The 1st case is a driver may be
> > disabled in the kernel config. The 2nd case is the kernel version may
> > simply not have the dependent driver. This can happen if using a newer DT
> > (provided by firmware perhaps) with a stable kernel version. Deferred
> > probe issues can be difficult to debug especially if the console has
> > dependencies or userspace fails to boot to a shell.
> >
> > There are also cases like IOMMUs where only built-in drivers are
> > supported, so deferring probe after initcalls is not needed. The IOMMU
> > subsystem implemented its own mechanism to handle this using OF_DECLARE
> > linker sections.
> >
> > This commit adds makes ending deferred probe conditional on initcalls
> > being completed or a debug timeout. Subsystems or drivers may opt-in by
> > calling driver_deferred_probe_check_init_done() instead of
> > unconditionally returning -EPROBE_DEFER. They may use additional
> > information from DT or kernel's config to decide whether to continue to
> > defer probe or not.
> >
> > The timeout mechanism is intended for debug purposes and WARNs loudly.
> > The remaining deferred probe pending list will also be dumped after the
> > timeout. Not that this timeout won't work for the console which needs
> > to be enabled before userspace starts. However, if the console's
> > dependencies are resolved, then the kernel log will be printed (as
> > opposed to no output).
>
> So what happens if we have a set of modules which use deferred probing
> in order to work?

It is opt-in by subsystem or drivers and mainly intended for
subsystems which can be optional or only support built-in drivers.
However, I don't really envision many other users other than the ones
I converted (pinctrl, iommu, pm-domains). If you look at patch 3,
you'll see it is dependent on !CONFIG_MODULES.

For the timeout, well, that's for debugging only. If you get to the
point of loading sound modules, you probably don't need the timeout.
It's for debugging not booting.

> For example, with sound stuff built as modules, and auto-loaded in
> parallel by udev, the modules get added in a random order.  The
> modules have non-udev obvious dependencies between them (resource
> dependencies) which result in deferred probing being necessary to
> bring the device up.

Re: [PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Rob Herring]

On Mon, Jul 9, 2018 at 9:52 AM Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
>
> On Mon, Jul 09, 2018 at 09:41:48AM -0600, Rob Herring wrote:
> > Deferred probe will currently wait forever on dependent devices to probe,
> > but sometimes a driver will never exist. It's also not always critical for
> > a driver to exist. Platforms can rely on default configuration from the
> > bootloader or reset defaults for things such as pinctrl and power domains.
> > This is often the case with initial platform support until various drivers
> > get enabled. There's at least 2 scenarios where deferred probe can render
> > a platform broken. Both involve using a DT which has more devices and
> > dependencies than the kernel supports. The 1st case is a driver may be
> > disabled in the kernel config. The 2nd case is the kernel version may
> > simply not have the dependent driver. This can happen if using a newer DT
> > (provided by firmware perhaps) with a stable kernel version. Deferred
> > probe issues can be difficult to debug especially if the console has
> > dependencies or userspace fails to boot to a shell.
> >
> > There are also cases like IOMMUs where only built-in drivers are
> > supported, so deferring probe after initcalls is not needed. The IOMMU
> > subsystem implemented its own mechanism to handle this using OF_DECLARE
> > linker sections.
> >
> > This commit adds makes ending deferred probe conditional on initcalls
> > being completed or a debug timeout. Subsystems or drivers may opt-in by
> > calling driver_deferred_probe_check_init_done() instead of
> > unconditionally returning -EPROBE_DEFER. They may use additional
> > information from DT or kernel's config to decide whether to continue to
> > defer probe or not.
> >
> > The timeout mechanism is intended for debug purposes and WARNs loudly.
> > The remaining deferred probe pending list will also be dumped after the
> > timeout. Not that this timeout won't work for the console which needs
> > to be enabled before userspace starts. However, if the console's
> > dependencies are resolved, then the kernel log will be printed (as
> > opposed to no output).
>
> So what happens if we have a set of modules which use deferred probing
> in order to work?

It is opt-in by subsystem or drivers and mainly intended for
subsystems which can be optional or only support built-in drivers.
However, I don't really envision many other users other than the ones
I converted (pinctrl, iommu, pm-domains). If you look at patch 3,
you'll see it is dependent on !CONFIG_MODULES.

For the timeout, well, that's for debugging only. If you get to the
point of loading sound modules, you probably don't need the timeout.
It's for debugging not booting.

> For example, with sound stuff built as modules, and auto-loaded in
> parallel by udev, the modules get added in a random order.  The
> modules have non-udev obvious dependencies between them (resource
> dependencies) which result in deferred probing being necessary to
> bring the device up.

[PATCH v4 1/6] driver core: allow stopping deferred probe after init

[Rob Herring]

On Mon, Jul 9, 2018 at 9:52 AM Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
>
> On Mon, Jul 09, 2018 at 09:41:48AM -0600, Rob Herring wrote:
> > Deferred probe will currently wait forever on dependent devices to probe,
> > but sometimes a driver will never exist. It's also not always critical for
> > a driver to exist. Platforms can rely on default configuration from the
> > bootloader or reset defaults for things such as pinctrl and power domains.
> > This is often the case with initial platform support until various drivers
> > get enabled. There's at least 2 scenarios where deferred probe can render
> > a platform broken. Both involve using a DT which has more devices and
> > dependencies than the kernel supports. The 1st case is a driver may be
> > disabled in the kernel config. The 2nd case is the kernel version may
> > simply not have the dependent driver. This can happen if using a newer DT
> > (provided by firmware perhaps) with a stable kernel version. Deferred
> > probe issues can be difficult to debug especially if the console has
> > dependencies or userspace fails to boot to a shell.
> >
> > There are also cases like IOMMUs where only built-in drivers are
> > supported, so deferring probe after initcalls is not needed. The IOMMU
> > subsystem implemented its own mechanism to handle this using OF_DECLARE
> > linker sections.
> >
> > This commit adds makes ending deferred probe conditional on initcalls
> > being completed or a debug timeout. Subsystems or drivers may opt-in by
> > calling driver_deferred_probe_check_init_done() instead of
> > unconditionally returning -EPROBE_DEFER. They may use additional
> > information from DT or kernel's config to decide whether to continue to
> > defer probe or not.
> >
> > The timeout mechanism is intended for debug purposes and WARNs loudly.
> > The remaining deferred probe pending list will also be dumped after the
> > timeout. Not that this timeout won't work for the console which needs
> > to be enabled before userspace starts. However, if the console's
> > dependencies are resolved, then the kernel log will be printed (as
> > opposed to no output).
>
> So what happens if we have a set of modules which use deferred probing
> in order to work?

It is opt-in by subsystem or drivers and mainly intended for
subsystems which can be optional or only support built-in drivers.
However, I don't really envision many other users other than the ones
I converted (pinctrl, iommu, pm-domains). If you look at patch 3,
you'll see it is dependent on !CONFIG_MODULES.

For the timeout, well, that's for debugging only. If you get to the
point of loading sound modules, you probably don't need the timeout.
It's for debugging not booting.

> For example, with sound stuff built as modules, and auto-loaded in
> parallel by udev, the modules get added in a random order.  The
> modules have non-udev obvious dependencies between them (resource
> dependencies) which result in deferred probing being necessary to
> bring the device up.

Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
> All PM domain drivers must be built-in (at least those using DT), so
> there is no point deferring probe after initcalls are done. Continuing
> to defer probe may prevent booting successfully even if managing PM
> domains is not required. This can happen if the user failed to enable
> the driver or if power-domains are added to a platform's DT, but there
> is not yet a driver (e.g. a new DTB with an old kernel).
>
> Call the driver core function driver_deferred_probe_check_init_done()
> instead of just returning -EPROBE_DEFER to stop deferring probe when
> initcalls are done.
>
> Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Kevin Hilman <khilman@kernel.org>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-pm@vger.kernel.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> v4:
>  - Add Rafael's ack
>
> v3:
>   - Update to new function name
>
>  drivers/base/power/domain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 4925af5c4cf0..8c12213875c6 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>                 mutex_unlock(&gpd_list_lock);
>                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>                         __func__, PTR_ERR(pd));
> -               return -EPROBE_DEFER;
> +               return driver_deferred_probe_check_state(dev);
>         }

This isn't the only error path where -EPROBE_DEFER may be returned
during attach in genpd.

Have a look at the callers of __genpd_dev_pm_attach() and also have a
second look inside __genpd_dev_pm_attach() itself. And in Rafael's
tree.

>
>         dev_dbg(dev, "adding to PM domain %s\n", pd->name);
> --
> 2.17.1

Besides the above, I am fine with the approach as such.

Kind regards
Uffe

[PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
> All PM domain drivers must be built-in (at least those using DT), so
> there is no point deferring probe after initcalls are done. Continuing
> to defer probe may prevent booting successfully even if managing PM
> domains is not required. This can happen if the user failed to enable
> the driver or if power-domains are added to a platform's DT, but there
> is not yet a driver (e.g. a new DTB with an old kernel).
>
> Call the driver core function driver_deferred_probe_check_init_done()
> instead of just returning -EPROBE_DEFER to stop deferring probe when
> initcalls are done.
>
> Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Kevin Hilman <khilman@kernel.org>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-pm at vger.kernel.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> v4:
>  - Add Rafael's ack
>
> v3:
>   - Update to new function name
>
>  drivers/base/power/domain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 4925af5c4cf0..8c12213875c6 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>                 mutex_unlock(&gpd_list_lock);
>                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>                         __func__, PTR_ERR(pd));
> -               return -EPROBE_DEFER;
> +               return driver_deferred_probe_check_state(dev);
>         }

This isn't the only error path where -EPROBE_DEFER may be returned
during attach in genpd.

Have a look at the callers of __genpd_dev_pm_attach() and also have a
second look inside __genpd_dev_pm_attach() itself. And in Rafael's
tree.

>
>         dev_dbg(dev, "adding to PM domain %s\n", pd->name);
> --
> 2.17.1

Besides the above, I am fine with the approach as such.

Kind regards
Uffe

Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Rob Herring]

On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
> > All PM domain drivers must be built-in (at least those using DT), so
> > there is no point deferring probe after initcalls are done. Continuing
> > to defer probe may prevent booting successfully even if managing PM
> > domains is not required. This can happen if the user failed to enable
> > the driver or if power-domains are added to a platform's DT, but there
> > is not yet a driver (e.g. a new DTB with an old kernel).
> >
> > Call the driver core function driver_deferred_probe_check_init_done()
> > instead of just returning -EPROBE_DEFER to stop deferring probe when
> > initcalls are done.
> >
> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Kevin Hilman <khilman@kernel.org>
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Len Brown <len.brown@intel.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: linux-pm@vger.kernel.org
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > ---
> > v4:
> >  - Add Rafael's ack
> >
> > v3:
> >   - Update to new function name
> >
> >  drivers/base/power/domain.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 4925af5c4cf0..8c12213875c6 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
> >                 mutex_unlock(&gpd_list_lock);
> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> >                         __func__, PTR_ERR(pd));
> > -               return -EPROBE_DEFER;
> > +               return driver_deferred_probe_check_state(dev);
> >         }
>
> This isn't the only error path where -EPROBE_DEFER may be returned
> during attach in genpd.

Yes, but I think this is the only place you can fail to get the PD
device from DT. The case we care about is properties exist in the DT,
but no driver exists.

What would cause deferring in the latter cases?

Rob

Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Rob Herring]

On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
> > All PM domain drivers must be built-in (at least those using DT), so
> > there is no point deferring probe after initcalls are done. Continuing
> > to defer probe may prevent booting successfully even if managing PM
> > domains is not required. This can happen if the user failed to enable
> > the driver or if power-domains are added to a platform's DT, but there
> > is not yet a driver (e.g. a new DTB with an old kernel).
> >
> > Call the driver core function driver_deferred_probe_check_init_done()
> > instead of just returning -EPROBE_DEFER to stop deferring probe when
> > initcalls are done.
> >
> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Kevin Hilman <khilman@kernel.org>
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Len Brown <len.brown@intel.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: linux-pm@vger.kernel.org
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > ---
> > v4:
> >  - Add Rafael's ack
> >
> > v3:
> >   - Update to new function name
> >
> >  drivers/base/power/domain.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 4925af5c4cf0..8c12213875c6 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
> >                 mutex_unlock(&gpd_list_lock);
> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> >                         __func__, PTR_ERR(pd));
> > -               return -EPROBE_DEFER;
> > +               return driver_deferred_probe_check_state(dev);
> >         }
>
> This isn't the only error path where -EPROBE_DEFER may be returned
> during attach in genpd.

Yes, but I think this is the only place you can fail to get the PD
device from DT. The case we care about is properties exist in the DT,
but no driver exists.

What would cause deferring in the latter cases?

Rob

[PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Rob Herring]

On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
> > All PM domain drivers must be built-in (at least those using DT), so
> > there is no point deferring probe after initcalls are done. Continuing
> > to defer probe may prevent booting successfully even if managing PM
> > domains is not required. This can happen if the user failed to enable
> > the driver or if power-domains are added to a platform's DT, but there
> > is not yet a driver (e.g. a new DTB with an old kernel).
> >
> > Call the driver core function driver_deferred_probe_check_init_done()
> > instead of just returning -EPROBE_DEFER to stop deferring probe when
> > initcalls are done.
> >
> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Kevin Hilman <khilman@kernel.org>
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Len Brown <len.brown@intel.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: linux-pm at vger.kernel.org
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > ---
> > v4:
> >  - Add Rafael's ack
> >
> > v3:
> >   - Update to new function name
> >
> >  drivers/base/power/domain.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 4925af5c4cf0..8c12213875c6 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
> >                 mutex_unlock(&gpd_list_lock);
> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> >                         __func__, PTR_ERR(pd));
> > -               return -EPROBE_DEFER;
> > +               return driver_deferred_probe_check_state(dev);
> >         }
>
> This isn't the only error path where -EPROBE_DEFER may be returned
> during attach in genpd.

Yes, but I think this is the only place you can fail to get the PD
device from DT. The case we care about is properties exist in the DT,
but no driver exists.

What would cause deferring in the latter cases?

Rob

Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 10 July 2018 at 16:25, Rob Herring <robh@kernel.org> wrote:
> On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>
>> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
>> > All PM domain drivers must be built-in (at least those using DT), so
>> > there is no point deferring probe after initcalls are done. Continuing
>> > to defer probe may prevent booting successfully even if managing PM
>> > domains is not required. This can happen if the user failed to enable
>> > the driver or if power-domains are added to a platform's DT, but there
>> > is not yet a driver (e.g. a new DTB with an old kernel).
>> >
>> > Call the driver core function driver_deferred_probe_check_init_done()
>> > instead of just returning -EPROBE_DEFER to stop deferring probe when
>> > initcalls are done.
>> >
>> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> > Cc: Kevin Hilman <khilman@kernel.org>
>> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
>> > Cc: Pavel Machek <pavel@ucw.cz>
>> > Cc: Len Brown <len.brown@intel.com>
>> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> > Cc: linux-pm@vger.kernel.org
>> > Signed-off-by: Rob Herring <robh@kernel.org>
>> > ---
>> > v4:
>> >  - Add Rafael's ack
>> >
>> > v3:
>> >   - Update to new function name
>> >
>> >  drivers/base/power/domain.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> > index 4925af5c4cf0..8c12213875c6 100644
>> > --- a/drivers/base/power/domain.c
>> > +++ b/drivers/base/power/domain.c
>> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>> >                 mutex_unlock(&gpd_list_lock);
>> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>> >                         __func__, PTR_ERR(pd));
>> > -               return -EPROBE_DEFER;
>> > +               return driver_deferred_probe_check_state(dev);
>> >         }
>>
>> This isn't the only error path where -EPROBE_DEFER may be returned
>> during attach in genpd.
>
> Yes, but I think this is the only place you can fail to get the PD
> device from DT. The case we care about is properties exist in the DT,
> but no driver exists.

That's correct. Thanks for clarifying!

>
> What would cause deferring in the latter cases?

To power on the PM domain for example, which often is required to be
able to probe the device.

>
> Rob

Kind regards
Uffe

Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 10 July 2018 at 16:25, Rob Herring <robh@kernel.org> wrote:
> On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>
>> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
>> > All PM domain drivers must be built-in (at least those using DT), so
>> > there is no point deferring probe after initcalls are done. Continuing
>> > to defer probe may prevent booting successfully even if managing PM
>> > domains is not required. This can happen if the user failed to enable
>> > the driver or if power-domains are added to a platform's DT, but there
>> > is not yet a driver (e.g. a new DTB with an old kernel).
>> >
>> > Call the driver core function driver_deferred_probe_check_init_done()
>> > instead of just returning -EPROBE_DEFER to stop deferring probe when
>> > initcalls are done.
>> >
>> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> > Cc: Kevin Hilman <khilman@kernel.org>
>> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
>> > Cc: Pavel Machek <pavel@ucw.cz>
>> > Cc: Len Brown <len.brown@intel.com>
>> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> > Cc: linux-pm@vger.kernel.org
>> > Signed-off-by: Rob Herring <robh@kernel.org>
>> > ---
>> > v4:
>> >  - Add Rafael's ack
>> >
>> > v3:
>> >   - Update to new function name
>> >
>> >  drivers/base/power/domain.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> > index 4925af5c4cf0..8c12213875c6 100644
>> > --- a/drivers/base/power/domain.c
>> > +++ b/drivers/base/power/domain.c
>> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>> >                 mutex_unlock(&gpd_list_lock);
>> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>> >                         __func__, PTR_ERR(pd));
>> > -               return -EPROBE_DEFER;
>> > +               return driver_deferred_probe_check_state(dev);
>> >         }
>>
>> This isn't the only error path where -EPROBE_DEFER may be returned
>> during attach in genpd.
>
> Yes, but I think this is the only place you can fail to get the PD
> device from DT. The case we care about is properties exist in the DT,
> but no driver exists.

That's correct. Thanks for clarifying!

>
> What would cause deferring in the latter cases?

To power on the PM domain for example, which often is required to be
able to probe the device.

>
> Rob

Kind regards
Uffe

[PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 10 July 2018 at 16:25, Rob Herring <robh@kernel.org> wrote:
> On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>
>> On 9 July 2018 at 17:41, Rob Herring <robh@kernel.org> wrote:
>> > All PM domain drivers must be built-in (at least those using DT), so
>> > there is no point deferring probe after initcalls are done. Continuing
>> > to defer probe may prevent booting successfully even if managing PM
>> > domains is not required. This can happen if the user failed to enable
>> > the driver or if power-domains are added to a platform's DT, but there
>> > is not yet a driver (e.g. a new DTB with an old kernel).
>> >
>> > Call the driver core function driver_deferred_probe_check_init_done()
>> > instead of just returning -EPROBE_DEFER to stop deferring probe when
>> > initcalls are done.
>> >
>> > Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> > Cc: Kevin Hilman <khilman@kernel.org>
>> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
>> > Cc: Pavel Machek <pavel@ucw.cz>
>> > Cc: Len Brown <len.brown@intel.com>
>> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> > Cc: linux-pm at vger.kernel.org
>> > Signed-off-by: Rob Herring <robh@kernel.org>
>> > ---
>> > v4:
>> >  - Add Rafael's ack
>> >
>> > v3:
>> >   - Update to new function name
>> >
>> >  drivers/base/power/domain.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> > index 4925af5c4cf0..8c12213875c6 100644
>> > --- a/drivers/base/power/domain.c
>> > +++ b/drivers/base/power/domain.c
>> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>> >                 mutex_unlock(&gpd_list_lock);
>> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>> >                         __func__, PTR_ERR(pd));
>> > -               return -EPROBE_DEFER;
>> > +               return driver_deferred_probe_check_state(dev);
>> >         }
>>
>> This isn't the only error path where -EPROBE_DEFER may be returned
>> during attach in genpd.
>
> Yes, but I think this is the only place you can fail to get the PD
> device from DT. The case we care about is properties exist in the DT,
> but no driver exists.

That's correct. Thanks for clarifying!

>
> What would cause deferring in the latter cases?

To power on the PM domain for example, which often is required to be
able to probe the device.

>
> Rob

Kind regards
Uffe