linux-kernel - [PATCH 1/1] regmap: add fast_io_disable_irq property for regmap

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Date:	Tue, 7 Jul 2015 03:32:55 +0000
From:	周学文 <zhouxuewen@...econe.net>
To:	Mark Brown <broonie@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	肖翔 <xiaoxiang@...econe.net>
Subject: [PATCH 1/1] regmap: add fast_io_disable_irq property for
 regmap_config


(please ignore the last email which contain HTML format and was rejected, sorry for the inconvenience caused)

This patch aims to fix an issue when using the regmap function in different drivers.

I describe the issue here:

We want to use the the same regmap handler to access the same hardware module using syscon interface in different drivers.

Some driver will read the register in interrupt handler to get  the hardware information while other drivers will access some other registers by regmap at the same time, so there will be a synchronization issue because the spin_lock/spin_unlock is used in regmap_read/regmap_write. a dead lock maybe happen on the current CPU.

This patch adds a property named fast_io_disable_irq and when this property is set to true the spin_lock_irqsave/spin_lockirqrestore lock function will be used in regmap_read/regmap_write to disable the local IRQ when accessing the register to  avoid the lock issue.

Change-Id: I07424191f3ab65d3f89bfee81fe2b4422cf84e74
Signed-off-by: Xuewen Zhou <zhouxuewen@...omi.com>
---
 drivers/base/regmap/internal.h |  1 +
 drivers/base/regmap/regmap.c   | 18 +++++++++++++++++-
 include/linux/regmap.h         |  1 +
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 5a22bd3..6a66e6b 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -54,6 +54,7 @@ struct regmap {
  regmap_lock lock;
  regmap_unlock unlock;
  void *lock_arg; /* This is passed to lock/unlock functions */
+ unsigned long flags;
 
  struct device *dev; /* Device we do I/O on */
  void *work_buf;     /* Scratch buffer used to format I/O */
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 58cfb32..b9b188e 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -297,6 +297,18 @@ static void regmap_unlock_spinlock(void *__map)
  spin_unlock(&map->spinlock);
 }
 
+static void regmap_lock_spinlock_irqsave(void *__map)
+{
+ struct regmap *map = __map;
+ spin_lock_irqsave(&map->spinlock, map->flags);
+}
+
+static void regmap_unlock_spinlock_irqrestore(void *__map)
+{
+ struct regmap *map = __map;
+ spin_unlock_irqrestore(&map->spinlock, map->flags);
+}
+
 static void dev_get_regmap_release(struct device *dev, void *res)
 {
  /*
@@ -403,7 +415,11 @@ struct regmap *regmap_init(struct device *dev,
  map->unlock = config->unlock;
  map->lock_arg = config->lock_arg;
  } else {
- if ((bus && bus->fast_io) ||
+ if (config->fast_io_disable_irq) {
+ spin_lock_init(&map->spinlock);
+ map->lock = regmap_lock_spinlock_irqsave;
+ map->unlock = regmap_unlock_spinlock_irqrestore;
+ } else if ((bus && bus->fast_io) ||
     config->fast_io) {
  spin_lock_init(&map->spinlock);
  map->lock = regmap_lock_spinlock;
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index bf77dfd..ca3c637 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -193,6 +193,7 @@ struct regmap_config {
  int (*reg_write)(void *context, unsigned int reg, unsigned int val);
 
  bool fast_io;
+ bool fast_io_disable_irq;
 
  unsigned int max_register;
  const struct regmap_access_table *wr_table;
-- 


Best regards,
Xuewen Zhou      
View attachment "0001-regmap-add-fast_io_disable_irq-property-for-regmap_c.patch" of type "text/x-patch" (3041 bytes)