[PATCH v1 1/1] gpio: mlxbf3: Support shutdown() function

[Asmaa Mnebhi <asmaa@nvidia.com>]

During Linux graceful reboot, the GPIO interrupts are not disabled.
Since the drivers are not removed during graceful reboot,
the logic to call mlxbf3_gpio_irq_disable() is not triggered.
Interrupts that remain enabled can cause issues on subsequent boots.

For example, the mlxbf-gige driver contains PHY logic to bring up the link.
If the gpio-mlxbf3 driver loads first, the mlxbf-gige driver
will use a GPIO interrupt to bring up the link.
Otherwise, it will use polling.
The next time Linux boots and loads the drivers in this order, we encounter the issue:
- mlxbf-gige loads first. The gige driver uses polling while the GPIO10 interrupt
  is still enabled from previous boot so if the interrupt triggers, there is nothing
  to clear it.
- gpio-mlxbf3 loads.
- i2c-mlxbf loads. The interrupt doesn't trigger for I2C because it is shared with the gpio
  interrupt line which was not cleared.

The solution is to add a shutdown function to the gpio driver to clear and disable
all interrupts. Also clear the interrupt after disabling it in mlxbf3_gpio_irq_disable().

Fixes: 38a700efc510 ("gpio: mlxbf3: Add gpio driver support")
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
---
 drivers/gpio/gpio-mlxbf3.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpio/gpio-mlxbf3.c b/drivers/gpio/gpio-mlxbf3.c
index d5906d419b0a..40bd93e3d695 100644
--- a/drivers/gpio/gpio-mlxbf3.c
+++ b/drivers/gpio/gpio-mlxbf3.c
@@ -39,6 +39,8 @@
 #define MLXBF_GPIO_CAUSE_OR_EVTEN0        0x14
 #define MLXBF_GPIO_CAUSE_OR_CLRCAUSE      0x18
 
+#define MLXBF_GPIO_CLR_ALL_INTS           0xFFFFFFFF
+
 struct mlxbf3_gpio_context {
 	struct gpio_chip gc;
 
@@ -82,6 +84,8 @@ static void mlxbf3_gpio_irq_disable(struct irq_data *irqd)
 	val = readl(gs->gpio_cause_io + MLXBF_GPIO_CAUSE_OR_EVTEN0);
 	val &= ~BIT(offset);
 	writel(val, gs->gpio_cause_io + MLXBF_GPIO_CAUSE_OR_EVTEN0);
+
+	writel(BIT(offset), gs->gpio_cause_io + MLXBF_GPIO_CAUSE_OR_CLRCAUSE);
 	raw_spin_unlock_irqrestore(&gs->gc.bgpio_lock, flags);
 
 	gpiochip_disable_irq(gc, offset);
@@ -253,6 +257,15 @@ static int mlxbf3_gpio_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static void mlxbf3_gpio_shutdown(struct platform_device *pdev)
+{
+	struct mlxbf3_gpio_context *gs = dev_get_drvdata(&pdev->dev);
+
+	/* Disable and clear all interrupts */
+	writel(0, gs->gpio_cause_io + MLXBF_GPIO_CAUSE_OR_EVTEN0);
+	writel(MLXBF_GPIO_CLR_ALL_INTS, gs->gpio_cause_io + MLXBF_GPIO_CAUSE_OR_CLRCAUSE);
+}
+
 static const struct acpi_device_id mlxbf3_gpio_acpi_match[] = {
 	{ "MLNXBF33", 0 },
 	{}
@@ -265,6 +278,7 @@ static struct platform_driver mlxbf3_gpio_driver = {
 		.acpi_match_table = mlxbf3_gpio_acpi_match,
 	},
 	.probe    = mlxbf3_gpio_probe,
+	.shutdown = mlxbf3_gpio_shutdown,
 };
 module_platform_driver(mlxbf3_gpio_driver);
 
-- 
2.30.1