ARM: SAMSUNG: Add spinlock locking to GPIO banks

Add locking to each GPIO bank to allow for SMP capable code
to use the gpiolib functions. See the gpio-core.h header file
for more information.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/arm/plat-samsung/include/plat/gpio-core.h b/arch/arm/plat-samsung/include/plat/gpio-core.h
index f0584f26d493..f3a68d1a07b9 100644
--- a/arch/arm/plat-samsung/include/plat/gpio-core.h
+++ b/arch/arm/plat-samsung/include/plat/gpio-core.h
@@ -44,16 +44,26 @@ struct s3c_gpio_cfg;
  * @chip: The chip structure to be exported via gpiolib.
  * @base: The base pointer to the gpio configuration registers.
  * @config: special function and pull-resistor control information.
+ * @lock: Lock for exclusive access to this gpio bank.
  * @pm_save: Save information for suspend/resume support.
  *
  * This wrapper provides the necessary information for the Samsung
  * specific gpios being registered with gpiolib.
+ *
+ * The lock protects each gpio bank from multiple access of the shared
+ * configuration registers, or from reading of data whilst another thread
+ * is writing to the register set.
+ *
+ * Each chip has its own lock to avoid any  contention between different
+ * CPU cores trying to get one lock for different GPIO banks, where each
+ * bank of GPIO has its own register space and configuration registers.
  */
 struct s3c_gpio_chip {
         struct gpio_chip        chip;
         struct s3c_gpio_cfg     *config;
         struct s3c_gpio_pm      *pm;
         void __iomem            *base;
+        spinlock_t               lock;
 #ifdef CONFIG_PM
         u32                     pm_save[4];
 #endif
@@ -138,3 +148,7 @@ extern struct s3c_gpio_pm s3c_gpio_pm_4bit;
 #define __gpio_pm(x) NULL
 
 #endif /* CONFIG_PM */
+
+/* locking wrappers to deal with multiple access to the same gpio bank */
+#define s3c_gpio_lock(_oc, _fl) spin_lock_irqsave(&(_oc)->lock, _fl)
+#define s3c_gpio_unlock(_oc, _fl) spin_unlock_irqrestore(&(_oc)->lock, _fl)