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

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

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

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

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

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