[PATCH] mfd: axp20x: Add a 500ms delay at the end of axp20x_power_off

[PATCH] mfd: axp20x: Add a 500ms delay at the end of axp20x_power_off

[Hans de Goede]

The kernel expects the power_off function to not return, and if it does
it panics. At a slight delay after the i2c write which turns off power
through the pmic, to give capacitors etc. some time to drain.

Without this the kernel lives on long enough after the poweroff to
print the following on the serial console on my Mele A1000G quad:

[  248.583588] reboot: Power down
[  248.600490] Kernel pa

With the delay the start of printing "Kernel panic" is gone.

Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/mfd/axp20x.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
index 6364dab..fd80b09 100644
--- a/drivers/mfd/axp20x.c
+++ b/drivers/mfd/axp20x.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -677,6 +678,9 @@ static void axp20x_power_off(void)
 
 	regmap_write(axp20x_pm_power_off->regmap, AXP20X_OFF_CTRL,
 		     AXP20X_OFF);
+
+	/* Give capacitors etc. time to drain to avoid kernel panic msg. */
+	msleep(500);
 }
 
 int axp20x_match_device(struct axp20x_dev *axp20x)
-- 
2.7.4

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Re: [PATCH] mfd: axp20x: Add a 500ms delay at the end of axp20x_power_off

[Chen-Yu Tsai]

On Sun, Jun 5, 2016 at 9:50 PM, Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> The kernel expects the power_off function to not return, and if it does
> it panics. At a slight delay after the i2c write which turns off power

             ^^^ Add?

Otherwise,

Acked-by: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>

> through the pmic, to give capacitors etc. some time to drain.
>
> Without this the kernel lives on long enough after the poweroff to
> print the following on the serial console on my Mele A1000G quad:
>
> [  248.583588] reboot: Power down
> [  248.600490] Kernel pa
>
> With the delay the start of printing "Kernel panic" is gone.
>
> Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/mfd/axp20x.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
> index 6364dab..fd80b09 100644
> --- a/drivers/mfd/axp20x.c
> +++ b/drivers/mfd/axp20x.c
> @@ -17,6 +17,7 @@
>   */
>
>  #include <linux/err.h>
> +#include <linux/delay.h>
>  #include <linux/interrupt.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> @@ -677,6 +678,9 @@ static void axp20x_power_off(void)
>
>         regmap_write(axp20x_pm_power_off->regmap, AXP20X_OFF_CTRL,
>                      AXP20X_OFF);
> +
> +       /* Give capacitors etc. time to drain to avoid kernel panic msg. */
> +       msleep(500);
>  }
>
>  int axp20x_match_device(struct axp20x_dev *axp20x)
> --
> 2.7.4
>
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Re: [PATCH] mfd: axp20x: Add a 500ms delay at the end of axp20x_power_off

[Lee Jones]

On Sun, 05 Jun 2016, Hans de Goede wrote:

> The kernel expects the power_off function to not return, and if it does
> it panics. At a slight delay after the i2c write which turns off power
> through the pmic, to give capacitors etc. some time to drain.
> 
> Without this the kernel lives on long enough after the poweroff to
> print the following on the serial console on my Mele A1000G quad:
> 
> [  248.583588] reboot: Power down
> [  248.600490] Kernel pa
> 
> With the delay the start of printing "Kernel panic" is gone.
> 
> Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/mfd/axp20x.c | 4 ++++
>  1 file changed, 4 insertions(+)

Applied, thanks.

> diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
> index 6364dab..fd80b09 100644
> --- a/drivers/mfd/axp20x.c
> +++ b/drivers/mfd/axp20x.c
> @@ -17,6 +17,7 @@
>   */
>  
>  #include <linux/err.h>
> +#include <linux/delay.h>
>  #include <linux/interrupt.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> @@ -677,6 +678,9 @@ static void axp20x_power_off(void)
>  
>  	regmap_write(axp20x_pm_power_off->regmap, AXP20X_OFF_CTRL,
>  		     AXP20X_OFF);
> +
> +	/* Give capacitors etc. time to drain to avoid kernel panic msg. */
> +	msleep(500);
>  }
>  
>  int axp20x_match_device(struct axp20x_dev *axp20x)

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Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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