linux-kernel - Re: [PATCH v8 4/4] media: pisp_be: Fix pm

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Message-ID: <CAEmqJPoxHSgXBp+EH+MWQVHVwYL2N5CnOwC-7W+AFWt1k7Zv+Q@mail.gmail.com>
Date: Tue, 17 Jun 2025 15:25:52 +0100
From: Naushir Patuck <naush@...pberrypi.com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>
Cc: Nick Hollinghurst <nick.hollinghurst@...pberrypi.com>, 
	David Plowman <david.plowman@...pberrypi.com>, 
	Dave Stevenson <dave.stevenson@...pberrypi.com>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.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 v8 4/4] media: pisp_be: Fix pm_runtime underrun in probe

Hi Jacopo,

Thank you for this fix.

On Tue, 17 Jun 2025 at 14:54, Jacopo Mondi
<jacopo.mondi@...asonboard.com> 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")
> Cc: stable@...r.kernel.org
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>

Tested-by: Naushir Patuck <naush@...pberrypi.com>
Reviewed-by: Naushir Patuck <naush@...pberrypi.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 46765a2e4c4d1573757ff842f208834216e582cb..a9e51fd94aadc6add70f883bfcea0c9fa91f0c4b 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 ccc6cb99868b842ac0d295f9ec28470303e60788..be794a12362020f42b3cf5bd291b4a1625543b5f 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -1725,7 +1725,7 @@ 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;
>
> @@ -1747,7 +1747,7 @@ 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);
> @@ -1761,7 +1761,6 @@ 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);
>  }
>
> --
> 2.49.0
>