[PATCH v2 0/2] 'force-mode' for gpio-poweroff driver

[PATCH v2 0/2] 'force-mode' for gpio-poweroff driver

[Oleksandr Suvorov]

This patch introduces a feature to force gpio-poweroff module
to register its own pm_power_off handler even if someone has registered
this handler earlier.
Useful to change a way to power off the system using DT files.

Changes in v2:
Call next pm_power_off handler if the current one
fails to power system off.

Oleksandr Suvorov (2):
  power: reset: gpio-poweroff: add force mode
  dt-bindings: power: reset: gpio-poweroff: Add 'force-mode' property

 .../bindings/power/reset/gpio-poweroff.txt    |  3 ++
 drivers/power/reset/gpio-poweroff.c           | 34 +++++++++++++++----
 2 files changed, 31 insertions(+), 6 deletions(-)

-- 
2.20.1

[PATCH v2 1/2] power: reset: gpio-poweroff: add force mode

[Oleksandr Suvorov]

Property "force-mode" tells the driver to replace previously
initialized power-off kernel hook and allows gpio-poweroff to
probe and operate successfully in any case.

Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
---

Changes in v2:
Call next pm_power_off handler if the current one
fails to power system off.

 drivers/power/reset/gpio-poweroff.c | 34 ++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/power/reset/gpio-poweroff.c b/drivers/power/reset/gpio-poweroff.c
index 6a4bbb506551..94056af9ba0d 100644
--- a/drivers/power/reset/gpio-poweroff.c
+++ b/drivers/power/reset/gpio-poweroff.c
@@ -24,6 +24,7 @@ static struct gpio_desc *reset_gpio;
 static u32 timeout = DEFAULT_TIMEOUT_MS;
 static u32 active_delay = 100;
 static u32 inactive_delay = 100;
+static void (*next_pm_power_off)(void);
 
 static void gpio_poweroff_do_poweroff(void)
 {
@@ -43,20 +44,41 @@ static void gpio_poweroff_do_poweroff(void)
 	/* give it some time */
 	mdelay(timeout);
 
+	/*
+	 * The kernel should not reach this code. If it does, fall back to
+	 * the next registered power off method.
+	 */
+	if (next_pm_power_off)
+		next_pm_power_off();
+
 	WARN_ON(1);
 }
 
 static int gpio_poweroff_probe(struct platform_device *pdev)
 {
 	bool input = false;
+	bool force = false;
 	enum gpiod_flags flags;
 
-	/* If a pm_power_off function has already been added, leave it alone */
+
+	force = device_property_read_bool(&pdev->dev, "force-mode");
+
+	/*
+	 * If a pm_power_off function has already been added, leave it alone,
+	 * if force-mode is not enabled.
+	 */
 	if (pm_power_off != NULL) {
-		dev_err(&pdev->dev,
-			"%s: pm_power_off function already registered",
-		       __func__);
-		return -EBUSY;
+		if (force) {
+			dev_warn(&pdev->dev,
+				 "%s: pm_power_off function replaced",
+				 __func__);
+			next_pm_power_off = pm_power_off;
+		} else {
+			dev_err(&pdev->dev,
+				"%s: pm_power_off function already registered",
+				__func__);
+			return -EBUSY;
+		}
 	}
 
 	input = device_property_read_bool(&pdev->dev, "input");
@@ -81,7 +103,7 @@ static int gpio_poweroff_probe(struct platform_device *pdev)
 static int gpio_poweroff_remove(struct platform_device *pdev)
 {
 	if (pm_power_off == &gpio_poweroff_do_poweroff)
-		pm_power_off = NULL;
+		pm_power_off = next_pm_power_off;
 
 	return 0;
 }
-- 
2.20.1

[PATCH v2 2/2] dt-bindings: power: reset: gpio-poweroff: Add 'force-mode' property

[Oleksandr Suvorov]

Add 'force-mode' property to allow the driver to load even if
someone has registered the pm_power_off hook earlier.

Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>

---

Changes in v2: None

 .../devicetree/bindings/power/reset/gpio-poweroff.txt          | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
index 3e56c1b34a4c..2056e299a472 100644
--- a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
+++ b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
@@ -31,6 +31,9 @@ Optional properties:
 - inactive-delay-ms: Delay (default 100) to wait after driving gpio inactive
 - timeout-ms: Time to wait before asserting a WARN_ON(1). If nothing is
               specified, 3000 ms is used.
+- force-mode: Force replacing pm_power_off kernel hook.
+  If this optional property is not specified, the driver will fail to
+  load if someone has registered the pm_power_off hook earlier.
 
 Examples:
 
-- 
2.20.1

Re: [PATCH v2 2/2] dt-bindings: power: reset: gpio-poweroff: Add 'force-mode' property

[Rob Herring]

On Mon, Sep 30, 2019 at 02:12:53PM +0000, Oleksandr Suvorov wrote:
> Add 'force-mode' property to allow the driver to load even if
> someone has registered the pm_power_off hook earlier.
> 
> Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
> 
> ---
> 
> Changes in v2: None
> 
>  .../devicetree/bindings/power/reset/gpio-poweroff.txt          | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> index 3e56c1b34a4c..2056e299a472 100644
> --- a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> +++ b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> @@ -31,6 +31,9 @@ Optional properties:
>  - inactive-delay-ms: Delay (default 100) to wait after driving gpio inactive
>  - timeout-ms: Time to wait before asserting a WARN_ON(1). If nothing is
>                specified, 3000 ms is used.
> +- force-mode: Force replacing pm_power_off kernel hook.
> +  If this optional property is not specified, the driver will fail to
> +  load if someone has registered the pm_power_off hook earlier.

What if the init order changes?

This is too tied to a specific OS implementation to go in DT.

Rob