[PATCH v4 2/2] gpio: sch: Hook into ACPI SCI handler to catch GPIO edge events

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

Neither the ACPI description on the Quark platform provides the required
information is to do establish generic handling nor hardware capable of
doing it. According to the datasheet the hardware can generate SCI events.
Therefore, we need to hook from the driver directly into SCI handler of
the ACPI subsystem in order to catch and report GPIO-related events.

Validated on the Quark-based IOT2000 platform.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Co-developed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 drivers/gpio/gpio-sch.c | 55 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/gpio/gpio-sch.c b/drivers/gpio/gpio-sch.c
index bbf8ee0b54de..022677d36a7c 100644
--- a/drivers/gpio/gpio-sch.c
+++ b/drivers/gpio/gpio-sch.c
@@ -26,6 +26,7 @@
 struct sch_gpio {
 	struct gpio_chip chip;
 	struct irq_chip irqchip;
+	acpi_sci_handler sci_handler;
 	spinlock_t lock;
 	unsigned short iobase;
 	unsigned short resume_base;
@@ -152,6 +153,28 @@ static const struct gpio_chip sch_gpio_chip = {
 	.get_direction		= sch_gpio_get_direction,
 };
 
+static u32 sch_gpio_sci_handler(void *context)
+{
+	struct sch_gpio *sch = context;
+	struct gpio_chip *gc = &sch->chip;
+	unsigned long core_status, resume_status;
+	unsigned long pending;
+	int offset;
+
+	core_status = inl(sch->iobase + GTS + 0x00);
+	resume_status = inl(sch->iobase + GTS + 0x20);
+
+	pending = (resume_status << sch->resume_base) | core_status;
+
+	for_each_set_bit(offset, &pending, sch->chip.ngpio)
+		generic_handle_irq(irq_find_mapping(gc->irq.domain, offset));
+
+	outl(core_status, sch->iobase + GTS + 0x00);
+	outl(resume_status, sch->iobase + GTS + 0x20);
+
+	return pending ? ACPI_INTERRUPT_HANDLED : ACPI_INTERRUPT_NOT_HANDLED;
+}
+
 static int sch_irq_type(struct irq_data *d, unsigned int type)
 {
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
@@ -211,10 +234,36 @@ static void sch_irq_unmask(struct irq_data *d)
 	sch_irq_set_enable(d, 1);
 }
 
+static void sch_gpio_remove_sci_handler(void *data)
+{
+	struct sch_gpio *sch = data;
+	struct device *dev = sch->chip.parent;
+	acpi_status status;
+
+	status = acpi_remove_sci_handler(sch->sci_handler);
+	if (ACPI_FAILURE(status))
+		dev_err(dev, "Can't remove SCI handler\n");
+}
+
+static int sch_gpio_install_sci_handler(struct sch_gpio *sch)
+{
+	struct device *dev = sch->chip.parent;
+	acpi_status status;
+
+	status = acpi_install_sci_handler(sch->sci_handler, sch);
+	if (ACPI_SUCCESS(status))
+		return devm_add_action_or_reset(dev, sch_gpio_remove_sci_handler, sch);
+
+	/* SCI handler is optional */
+	dev_warn(dev, "Can't install SCI handler, no IRQ support\n");
+	return 0;
+}
+
 static int sch_gpio_probe(struct platform_device *pdev)
 {
 	struct sch_gpio *sch;
 	struct resource *res;
+	int ret;
 
 	sch = devm_kzalloc(&pdev->dev, sizeof(*sch), GFP_KERNEL);
 	if (!sch)
@@ -286,6 +335,12 @@ static int sch_gpio_probe(struct platform_device *pdev)
 	sch->chip.irq.default_type = IRQ_TYPE_NONE;
 	sch->chip.irq.handler = handle_bad_irq;
 
+	sch->sci_handler = sch_gpio_sci_handler;
+
+	ret = sch_gpio_install_sci_handler(sch);
+	if (ret)
+		return ret;
+
 	return devm_gpiochip_add_data(&pdev->dev, &sch->chip, sch);
 }
 
-- 
2.30.2