[PATCH v2 2/2] gpio: tegra: Use raw_spinlock

[Dmitry Osipenko <digetx@gmail.com>]

Use raw_spinlock in order to fix spurious messages about invalid context
when spinlock debugging is enabled. This happens because there is a legit
nested raw_spinlock->spinlock locking usage within IRQ-related code. IRQ
core uses raw spinlock and then Tegra GPIO driver uses a nested spinlock.
The debug code can't recognize and handle this case, hence we need to use
raw spinlock in the GPIO driver.

 [ BUG: Invalid wait context ]
 ...
  (dump_stack) from (__lock_acquire)
  (__lock_acquire) from (lock_acquire)
  (lock_acquire) from (_raw_spin_lock_irqsave)
  (_raw_spin_lock_irqsave) from (tegra_gpio_irq_set_type)
  (tegra_gpio_irq_set_type) from (__irq_set_trigger)
  (__irq_set_trigger) from (__setup_irq)
  (__setup_irq) from (request_threaded_irq)
  (request_threaded_irq) from (devm_request_threaded_irq)
  (devm_request_threaded_irq) from (elants_i2c_probe)
  (elants_i2c_probe) from (i2c_device_probe)
 ...

Tested-by: Peter Geis <pgwipeout@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---

Changelog:

v2: - Only lvl_lock is converted to raw_spinlock. The dbc_lock doesn't
      relate to IRQ and doesn't need the conversion.

    - Improved commit message by clarifying that IRQ core uses raw
      spinlock.

    - Added clarifying comment to the code for the lvl_lock.

 drivers/gpio/gpio-tegra.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c
index 98fc78739ebf..e19ebff6018c 100644
--- a/drivers/gpio/gpio-tegra.c
+++ b/drivers/gpio/gpio-tegra.c
@@ -61,8 +61,16 @@ struct tegra_gpio_info;
 struct tegra_gpio_bank {
 	unsigned int bank;
 	unsigned int irq;
-	spinlock_t lvl_lock[4];
-	spinlock_t dbc_lock[4];	/* Lock for updating debounce count register */
+
+	/*
+	 * IRQ-core code uses raw locking, and thus, nested locking also
+	 * should be raw in order not to trip spinlock debug warnings.
+	 */
+	raw_spinlock_t lvl_lock[4];
+
+	/* Lock for updating debounce count register */
+	spinlock_t dbc_lock[4];
+
 #ifdef CONFIG_PM_SLEEP
 	u32 cnf[4];
 	u32 out[4];
@@ -334,14 +342,14 @@ static int tegra_gpio_irq_set_type(struct irq_data *d, unsigned int type)
 		return -EINVAL;
 	}
 
-	spin_lock_irqsave(&bank->lvl_lock[port], flags);
+	raw_spin_lock_irqsave(&bank->lvl_lock[port], flags);
 
 	val = tegra_gpio_readl(tgi, GPIO_INT_LVL(tgi, gpio));
 	val &= ~(GPIO_INT_LVL_MASK << GPIO_BIT(gpio));
 	val |= lvl_type << GPIO_BIT(gpio);
 	tegra_gpio_writel(tgi, val, GPIO_INT_LVL(tgi, gpio));
 
-	spin_unlock_irqrestore(&bank->lvl_lock[port], flags);
+	raw_spin_unlock_irqrestore(&bank->lvl_lock[port], flags);
 
 	tegra_gpio_mask_write(tgi, GPIO_MSK_OE(tgi, gpio), gpio, 0);
 	tegra_gpio_enable(tgi, gpio);
@@ -675,7 +683,7 @@ static int tegra_gpio_probe(struct platform_device *pdev)
 						 tegra_gpio_irq_handler, bank);
 
 		for (j = 0; j < 4; j++) {
-			spin_lock_init(&bank->lvl_lock[j]);
+			raw_spin_lock_init(&bank->lvl_lock[j]);
 			spin_lock_init(&bank->dbc_lock[j]);
 		}
 	}
-- 
2.27.0