linux-kernel - Re: [PATCH regression fix] misc: lis3lv02d_i2c: Fix regulators getting en-/dis-abled twice on suspend/resume

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Date: Fri, 1 Mar 2024 12:50:07 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Arnd Bergmann <arnd@...db.de>, Eric Piel <eric.piel@...mplin-utc.net>,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org,
 regressions@...ts.linux.dev
Subject: Re: [PATCH regression fix] misc: lis3lv02d_i2c: Fix regulators
 getting en-/dis-abled twice on suspend/resume

Dear Hans,


Thank you for the patch.

Am 20.02.24 um 20:00 schrieb Hans de Goede:
> When not configured for wakeup lis3lv02d_i2c_suspend() will call
> lis3lv02d_poweroff() even if the device has already been turned off
> by the runtime-suspend handler and if configured for wakeup and
> the device is runtime-suspended at this point then it is not turned
> back on to serve as a wakeup source.
> 
> Before commit b1b9f7a49440 ("misc: lis3lv02d_i2c: Add missing setting
> of the reg_ctrl callback"), lis3lv02d_poweroff() failed to disable
> the regulators which as a side effect made calling poweroff() twice ok.
> 
> Now that poweroff() correctly disables the regulators, doing this twice
> triggers a WARN() in the regulator core:
> 
> unbalanced disables for regulator-dummy
> WARNING: CPU: 1 PID: 92 at drivers/regulator/core.c:2999 _regulator_disable
> ...
> 
> Fix lis3lv02d_i2c_suspend() to not call poweroff() a second time if
> already runtime-suspended and add a poweron() call when necessary to
> make wakeup work.
> 
> lis3lv02d_i2c_resume() has similar issues, with an added weirness that
> it always powers on the device if it is runtime suspended, after which
> the first runtime-resume will call poweron() again, causing the enabled
> count for the regulator to increase by 1 every suspend/resume. These
> unbalanced regulator_enable() calls cause the regulator to never
> be turned off and trigger the following WARN() on driver unbind:
> 
> WARNING: CPU: 1 PID: 1724 at drivers/regulator/core.c:2396 _regulator_put
> 
> Fix this by making lis3lv02d_i2c_resume() mirror the new suspend().
> 
> Fixes: b1b9f7a49440 ("misc: lis3lv02d_i2c: Add missing setting of the reg_ctrl callback")
> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
> Closes: https://lore.kernel.org/regressions/5fc6da74-af0a-4aac-b4d5-a000b39a63a5@molgen.mpg.de/
> Cc: stable@...r.kernel.org
> Cc: regressions@...ts.linux.dev
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---
>   drivers/misc/lis3lv02d/lis3lv02d_i2c.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/misc/lis3lv02d/lis3lv02d_i2c.c b/drivers/misc/lis3lv02d/lis3lv02d_i2c.c
> index c6eb27d46cb0..15119584473c 100644
> --- a/drivers/misc/lis3lv02d/lis3lv02d_i2c.c
> +++ b/drivers/misc/lis3lv02d/lis3lv02d_i2c.c
> @@ -198,8 +198,14 @@ static int lis3lv02d_i2c_suspend(struct device *dev)
>   	struct i2c_client *client = to_i2c_client(dev);
>   	struct lis3lv02d *lis3 = i2c_get_clientdata(client);
>   
> -	if (!lis3->pdata || !lis3->pdata->wakeup_flags)
> +	/* Turn on for wakeup if turned off by runtime suspend */
> +	if (lis3->pdata && lis3->pdata->wakeup_flags) {
> +		if (pm_runtime_suspended(dev))
> +			lis3lv02d_poweron(lis3);
> +	/* For non wakeup turn off if not already turned off by runtime suspend */
> +	} else if (!pm_runtime_suspended(dev))
>   		lis3lv02d_poweroff(lis3);
> +
>   	return 0;
>   }
>   
> @@ -208,13 +214,12 @@ static int lis3lv02d_i2c_resume(struct device *dev)
>   	struct i2c_client *client = to_i2c_client(dev);
>   	struct lis3lv02d *lis3 = i2c_get_clientdata(client);
>   
> -	/*
> -	 * pm_runtime documentation says that devices should always
> -	 * be powered on at resume. Pm_runtime turns them off after system
> -	 * wide resume is complete.
> -	 */
> -	if (!lis3->pdata || !lis3->pdata->wakeup_flags ||
> -		pm_runtime_suspended(dev))
> +	/* Turn back off if turned on for wakeup and runtime suspended*/
> +	if (lis3->pdata && lis3->pdata->wakeup_flags) {
> +		if (pm_runtime_suspended(dev))
> +			lis3lv02d_poweroff(lis3);
> +	/* For non wakeup turn back on if not runtime suspended */
> +	} else if (!pm_runtime_suspended(dev))
>   		lis3lv02d_poweron(lis3);
>   
>   	return 0;

I applied this commit on top of Linus’ master branch, and successfully 
tested with S0ix and ACPI S3, that the warning is gone.

Tested-by: Paul Menzel <pmenzel@...gen.mpg.de> # Dell XPS 15 7590

Looking at the diff, this also looks good. Thank you for writing the 
helpful commit message.

Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>

Thank you for addressing this so quickly, and sorry for the late reply.


Kind regards,

Paul