gpiolib: irqchip: use different lockdep class for each gpio irqchip

Since IRQ chip helpers were introduced drivers lose ability to
register separate lockdep classes for each registered GPIO IRQ
chip and the gpiolib now is using shared lockdep class for
all GPIO IRQ chips (gpiochip_irq_lock_class).
As result, lockdep will produce warning when there are min two
stacked GPIO chips and all of them are interrupt controllers.

HW configuration which generates lockdep warning (TI dra7-evm):

[SOC GPIO bankA.gpioX]
  <- irq - [pcf875x.gpioY]
            <- irq - DevZ.enable_irq_wake(pcf_gpioY_irq);
The issue was reported in [1] and discussed [2].

=============================================
[ INFO: possible recursive locking detected ]
4.2.0-rc6-00013-g5d050ed-dirty #55 Not tainted
---------------------------------------------
sh/63 is trying to acquire lock:
 (class){......}, at: [<c009b91c>] __irq_get_desc_lock+0x50/0x94

but task is already holding lock:
 (class){......}, at: [<c009b91c>] __irq_get_desc_lock+0x50/0x94

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(class);
  lock(class);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

7 locks held by sh/63:
 #0:  (sb_writers#4){.+.+.+}, at: [<c016bbb8>] vfs_write+0x13c/0x164
 #1:  (&of->mutex){+.+.+.}, at: [<c01debf4>] kernfs_fop_write+0x4c/0x1a0
 #2:  (s_active#36){.+.+.+}, at: [<c01debfc>] kernfs_fop_write+0x54/0x1a0
 #3:  (pm_mutex){+.+.+.}, at: [<c009758c>] pm_suspend+0xec/0x4c4
 #4:  (&dev->mutex){......}, at: [<c03f77f8>] __device_suspend+0xd4/0x398
 #5:  (&gpio->lock){+.+.+.}, at: [<c009b940>] __irq_get_desc_lock+0x74/0x94
 #6:  (class){......}, at: [<c009b91c>] __irq_get_desc_lock+0x50/0x94

stack backtrace:
CPU: 0 PID: 63 Comm: sh Not tainted 4.2.0-rc6-00013-g5d050ed-dirty #55
Hardware name: Generic DRA74X (Flattened Device Tree)
[<c0016e24>] (unwind_backtrace) from [<c0013338>] (show_stack+0x10/0x14)
[<c0013338>] (show_stack) from [<c05f6b24>] (dump_stack+0x84/0x9c)
[<c05f6b24>] (dump_stack) from [<c00903f4>] (__lock_acquire+0x19c0/0x1e20)
[<c00903f4>] (__lock_acquire) from [<c0091098>] (lock_acquire+0xa8/0x128)
[<c0091098>] (lock_acquire) from [<c05fd61c>] (_raw_spin_lock_irqsave+0x38/0x4c)
[<c05fd61c>] (_raw_spin_lock_irqsave) from [<c009b91c>] (__irq_get_desc_lock+0x50/0x94)
[<c009b91c>] (__irq_get_desc_lock) from [<c009c4f4>] (irq_set_irq_wake+0x20/0xfc)
[<c009c4f4>] (irq_set_irq_wake) from [<c0393ac4>] (pcf857x_irq_set_wake+0x24/0x54)
[<c0393ac4>] (pcf857x_irq_set_wake) from [<c009c560>] (irq_set_irq_wake+0x8c/0xfc)
[<c009c560>] (irq_set_irq_wake) from [<c04a02ac>] (gpio_keys_suspend+0x70/0xd4)
[<c04a02ac>] (gpio_keys_suspend) from [<c03f6a00>] (dpm_run_callback+0x50/0x124)
[<c03f6a00>] (dpm_run_callback) from [<c03f7830>] (__device_suspend+0x10c/0x398)
[<c03f7830>] (__device_suspend) from [<c03f90f0>] (dpm_suspend+0x134/0x2f4)
[<c03f90f0>] (dpm_suspend) from [<c0096e20>] (suspend_devices_and_enter+0xa8/0x728)
[<c0096e20>] (suspend_devices_and_enter) from [<c00977cc>] (pm_suspend+0x32c/0x4c4)
[<c00977cc>] (pm_suspend) from [<c0096060>] (state_store+0x64/0xb8)
[<c0096060>] (state_store) from [<c01dec64>] (kernfs_fop_write+0xbc/0x1a0)
[<c01dec64>] (kernfs_fop_write) from [<c016b280>] (__vfs_write+0x20/0xd8)
[<c016b280>] (__vfs_write) from [<c016bb0c>] (vfs_write+0x90/0x164)
[<c016bb0c>] (vfs_write) from [<c016c330>] (SyS_write+0x44/0x9c)
[<c016c330>] (SyS_write) from [<c000f500>] (ret_fast_syscall+0x0/0x54)

Lets fix it by using separate lockdep class for each registered GPIO
IRQ Chip. This is done by wrapping gpiochip_irqchip_add call into macros.

The implementation of this patch inspired by solution done by Nicolas
Boichat for regmap [3]

[1] http://www.spinics.net/lists/linux-gpio/msg05844.html
[2] http://www.spinics.net/lists/linux-gpio/msg06021.html
[3] http://www.spinics.net/lists/arm-kernel/msg429834.html

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roger Quadros <rogerq@ti.com>
Reported-by: Roger Quadros <rogerq@ti.com>
Tested-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index c8393cd4d44f..0c7004dab437 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -6,6 +6,7 @@
 #include <linux/irq.h>
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
+#include <linux/lockdep.h>
 #include <linux/pinctrl/pinctrl.h>
 
 struct device;
@@ -126,6 +127,7 @@ struct gpio_chip {
 	irq_flow_handler_t	irq_handler;
 	unsigned int		irq_default_type;
 	int			irq_parent;
+	struct lock_class_key	*lock_key;
 #endif
 
 #if defined(CONFIG_OF_GPIO)
@@ -171,11 +173,25 @@ void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
 		int parent_irq,
 		irq_flow_handler_t parent_handler);
 
-int gpiochip_irqchip_add(struct gpio_chip *gpiochip,
-		struct irq_chip *irqchip,
-		unsigned int first_irq,
-		irq_flow_handler_t handler,
-		unsigned int type);
+int _gpiochip_irqchip_add(struct gpio_chip *gpiochip,
+			  struct irq_chip *irqchip,
+			  unsigned int first_irq,
+			  irq_flow_handler_t handler,
+			  unsigned int type,
+			  struct lock_class_key *lock_key);
+
+#ifdef CONFIG_LOCKDEP
+#define gpiochip_irqchip_add(...)				\
+(								\
+	({							\
+		static struct lock_class_key _key;		\
+		_gpiochip_irqchip_add(__VA_ARGS__, &_key);	\
+	})							\
+)
+#else
+#define gpiochip_irqchip_add(...)				\
+	_gpiochip_irqchip_add(__VA_ARGS__, NULL)
+#endif
 
 #endif /* CONFIG_GPIOLIB_IRQCHIP */