[PATCH] Input: gpio_keys: Add level trigger support for GPIO keys

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type. So this patch introduces one property to
indicate if the GPIO trigger type is level trigger or edge trigger.

Signed-off-by: Baolin Wang <redacted>
---
 .../devicetree/bindings/input/gpio-keys.txt        |    2 ++
 drivers/input/keyboard/gpio_keys.c                 |   22 +++++++++++++++++++-
 include/linux/gpio_keys.h                          |    1 +
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/input/gpio-keys.txt b/Documentation/devicetree/bindings/input/gpio-keys.txt
index a949404..e3104bd 100644
--- a/Documentation/devicetree/bindings/input/gpio-keys.txt
+++ b/Documentation/devicetree/bindings/input/gpio-keys.txt

@@ -29,6 +29,8 @@ Optional subnode-properties:
 	- linux,can-disable: Boolean, indicates that button is connected
 	  to dedicated (not shared) interrupt which can be disabled to
 	  suppress events from the button.
+	- gpio-key,level-trigger: Boolean, indicates that button's interrupt
+	  type is level trigger. Otherwise it is edge trigger as default.
 
 Example nodes:
 

diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index 87e613d..d3b4bb6 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c

@@ -385,6 +385,19 @@ static void gpio_keys_gpio_work_func(struct work_struct *work)
 	struct gpio_button_data *bdata =
 		container_of(work, struct gpio_button_data, work.work);
 
+	if (bdata->button->level_trigger) {
+		unsigned int trigger =
+			irq_get_trigger_type(bdata->irq) & ~IRQF_TRIGGER_MASK;
+		int state = gpiod_get_raw_value_cansleep(bdata->gpiod);
+
+		if (state)
+			trigger |= IRQF_TRIGGER_LOW;
+		else
+			trigger |= IRQF_TRIGGER_HIGH;
+
+		irq_set_irq_type(bdata->irq, trigger);
+	}
+
 	gpio_keys_gpio_report_event(bdata);
 
 	if (bdata->button->wakeup)

@@ -566,7 +579,11 @@ static int gpio_keys_setup_key(struct platform_device *pdev,
 		INIT_DELAYED_WORK(&bdata->work, gpio_keys_gpio_work_func);
 
 		isr = gpio_keys_gpio_isr;
-		irqflags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;
+		if (button->level_trigger)
+			irqflags = gpiod_is_active_low(bdata->gpiod) ?
+				IRQF_TRIGGER_LOW : IRQF_TRIGGER_HIGH;
+		else
+			irqflags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;
 
 	} else {
 		if (!button->irq) {

@@ -721,6 +738,9 @@ static void gpio_keys_close(struct input_dev *input)
 		button->can_disable =
 			fwnode_property_read_bool(child, "linux,can-disable");
 
+		button->level_trigger =
+			fwnode_property_read_bool(child, "gpio-key,level-trigger");
+
 		if (fwnode_property_read_u32(child, "debounce-interval",
 					 &button->debounce_interval))
 			button->debounce_interval = 5;

diff --git a/include/linux/gpio_keys.h b/include/linux/gpio_keys.h
index d06bf77..5095645 100644
--- a/include/linux/gpio_keys.h
+++ b/include/linux/gpio_keys.h

@@ -28,6 +28,7 @@ struct gpio_keys_button {
 	int wakeup;
 	int debounce_interval;
 	bool can_disable;
+	bool level_trigger;
 	int value;
 	unsigned int irq;
 };

-- 
1.7.9.5

On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang [off-list ref] wrote:

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type.

How do you stop the interrupt from re-triggering as long as the key
stays pressed?

Thanks.

-- 
Dmitry
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On 9 February 2018 at 14:39, Dmitry Torokhov [off-list ref] wrote:

On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang [off-list ref] wrote:

quoted

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type.

How do you stop the interrupt from re-triggering as long as the key
stays pressed?

We will set the level type irq handler as handle_level_irq(), in this
function, it will mask and ack the irq firstly.

-- 
Baolin.wang
Best Regards
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On Fri, Feb 9, 2018 at 11:23 AM, Baolin Wang [off-list ref] wrote:

On 9 February 2018 at 14:39, Dmitry Torokhov [off-list ref] wrote:

quoted

On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang [off-list ref] wrote:

quoted

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type.

How do you stop the interrupt from re-triggering as long as the key
stays pressed?

We will set the level type irq handler as handle_level_irq(), in this
function, it will mask and ack the irq firstly.

Wouldn't be ambiguous?

1. User presses the key ->
  a) we got edge followed by level signaling;
  b) IRQ core masks line, calls handler, ACKs, unmasks;
  c) somewhere here Press Event is sent;
  d) we still have level... We get IRQ fired again? But see 1. It
obviously not the case.
2. User releases the key ->
  ...

So, the main question if I understood Dmitry correctly is the period
in time where IRQ line should be masked on one hand, and on the other
it will guarantee that user didn't release-press cylcle.

-- 
With Best Regards,
Andy Shevchenko
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On 9 February 2018 at 23:03, Andy Shevchenko [off-list ref] wrote:

On Fri, Feb 9, 2018 at 11:23 AM, Baolin Wang [off-list ref] wrote:

quoted

On 9 February 2018 at 14:39, Dmitry Torokhov [off-list ref] wrote:

quoted

On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang [off-list ref] wrote:

quoted

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type.

How do you stop the interrupt from re-triggering as long as the key
stays pressed?

We will set the level type irq handler as handle_level_irq(), in this
function, it will mask and ack the irq firstly.

Wouldn't be ambiguous?

1. User presses the key ->
  a) we got edge followed by level signaling;
  b) IRQ core masks line, calls handler, ACKs, unmasks;
  c) somewhere here Press Event is sent;
  d) we still have level... We get IRQ fired again? But see 1. It
obviously not the case.
2. User releases the key ->
  ...

So, the main question if I understood Dmitry correctly is the period
in time where IRQ line should be masked on one hand, and on the other
it will guarantee that user didn't release-press cylcle.

Yes, you and Dmitry are right. I realized my problem. When I tested on
Spreadtrum platform, we use Spreadtrum-special EIC (external interrupt
controller) to trigger button events, if we acked the EIC irq, it will
drop the interrupt line and never trigger events until we set irq type
again. But this can not work for general GPIOs like you said.

So I think I need disable the irq until reversing the level type. Thanks.

-- 
Baolin.wang
Best Regards
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