linux-kernel - Re: [PATCH v7 4/4] media: pisp_be: Fix pm

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Message-ID: <20250616141756.GC32454@pendragon.ideasonboard.com>
Date: Mon, 16 Jun 2025 17:17:56 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>
Cc: Naushir Patuck <naush@...pberrypi.com>,
	Nick Hollinghurst <nick.hollinghurst@...pberrypi.com>,
	David Plowman <david.plowman@...pberrypi.com>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v7 4/4] media: pisp_be: Fix pm_runtime underrun in probe

Hi Jacopo,

Thank you for the patch.

On Fri, Jun 06, 2025 at 12:29:24PM +0200, Jacopo Mondi wrote:
> During the probe() routine, the PiSP BE driver needs to power up the
> interface in order to identify and initialize the hardware.
> 
> The driver resumes the interface by calling the
> pispbe_runtime_resume() function directly, without going
> through the pm_runtime helpers, but later suspends it by calling
> pm_runtime_put_autosuspend().
> 
> This causes a PM usage count imbalance at probe time, notified by the
> runtime_pm framework with the below message in the system log:
> 
>  pispbe 1000880000.pisp_be: Runtime PM usage count underflow!
> 
> Fix this by resuming the interface using the pm runtime helpers instead
> of calling the resume function directly and use the pm_runtime framework
> in the probe() error path. While at it, remove manual suspend of the
> interface in the remove() function. The driver cannot be unloaded if in
> use, so simply disable runtime pm.
> 
> To simplify the implementation, make the driver depend on PM as the
> RPI5 platform where the ISP is integrated in uses the PM framework by
> default.
> 
> Fixes: 12187bd5d4f8 ("media: raspberrypi: Add support for PiSP BE")
> Signed-off-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> 
> --
> 
> Cc: stable@...r.kernel.org

This should go just below the Fixes: tag.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/media/platform/raspberrypi/pisp_be/Kconfig   | 1 +
>  drivers/media/platform/raspberrypi/pisp_be/pisp_be.c | 5 ++---
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/Kconfig b/drivers/media/platform/raspberrypi/pisp_be/Kconfig
> index 46765a2e4c4d..a9e51fd94aad 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/Kconfig
> +++ b/drivers/media/platform/raspberrypi/pisp_be/Kconfig
> @@ -3,6 +3,7 @@ config VIDEO_RASPBERRYPI_PISP_BE
>  	depends on V4L_PLATFORM_DRIVERS
>  	depends on VIDEO_DEV
>  	depends on ARCH_BCM2835 || COMPILE_TEST
> +	depends on PM
>  	select VIDEO_V4L2_SUBDEV_API
>  	select MEDIA_CONTROLLER
>  	select VIDEOBUF2_DMA_CONTIG
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> index c25f7d9b404c..e49e4cc322db 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -1718,7 +1718,7 @@ static int pispbe_probe(struct platform_device *pdev)
>  	pm_runtime_use_autosuspend(pispbe->dev);
>  	pm_runtime_enable(pispbe->dev);
>  
> -	ret = pispbe_runtime_resume(pispbe->dev);
> +	ret = pm_runtime_resume_and_get(pispbe->dev);
>  	if (ret)
>  		goto pm_runtime_disable_err;
>  
> @@ -1740,7 +1740,7 @@ static int pispbe_probe(struct platform_device *pdev)
>  disable_devs_err:
>  	pispbe_destroy_devices(pispbe);
>  pm_runtime_suspend_err:
> -	pispbe_runtime_suspend(pispbe->dev);
> +	pm_runtime_put(pispbe->dev);
>  pm_runtime_disable_err:
>  	pm_runtime_dont_use_autosuspend(pispbe->dev);
>  	pm_runtime_disable(pispbe->dev);
> @@ -1754,7 +1754,6 @@ static void pispbe_remove(struct platform_device *pdev)
>  
>  	pispbe_destroy_devices(pispbe);
>  
> -	pispbe_runtime_suspend(pispbe->dev);
>  	pm_runtime_dont_use_autosuspend(pispbe->dev);
>  	pm_runtime_disable(pispbe->dev);
>  }

-- 
Regards,

Laurent Pinchart