linux-kernel - Re: [PATCH 16/25] media: am437x: fix pm_runtime_get

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Message-ID: <CA+V-a8sLF-q13RaM-9g5XRtU_t_5Ztn5X7hsg=AdgMPOEpdTZA@mail.gmail.com>
Date:   Sat, 8 May 2021 14:01:51 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc:     linuxarm@...wei.com, mauro.chehab@...wei.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-media <linux-media@...r.kernel.org>
Subject: Re: [PATCH 16/25] media: am437x: fix pm_runtime_get_sync() usage count

Hi Mauro,

Thank you for the patch.

On Wed, May 5, 2021 at 10:42 AM Mauro Carvalho Chehab
<mchehab+huawei@...nel.org> wrote:
>
> The pm_runtime_get_sync() internally increments the
> dev->power.usage_count without decrementing it, even on errors.
> Replace it by the new pm_runtime_resume_and_get(), introduced by:
> commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> in order to properly decrement the usage counter, avoiding
> a potential PM usage counter leak.
>
> While here, ensure that the driver will check if PM runtime
> resumed at vpfe_initialize_device().
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> ---
>  drivers/media/platform/am437x/am437x-vpfe.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
Acked-by: Lad Prabhakar <prabhakar.csengg@...il.com>

Cheers,
Prabhakar


> diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
> index 6cdc77dda0e4..1c9cb9e05fdf 100644
> --- a/drivers/media/platform/am437x/am437x-vpfe.c
> +++ b/drivers/media/platform/am437x/am437x-vpfe.c
> @@ -1021,7 +1021,9 @@ static int vpfe_initialize_device(struct vpfe_device *vpfe)
>         if (ret)
>                 return ret;
>
> -       pm_runtime_get_sync(vpfe->pdev);
> +       ret = pm_runtime_resume_and_get(vpfe->pdev);
> +       if (ret < 0)
> +               return ret;
>
>         vpfe_config_enable(&vpfe->ccdc, 1);
>
> @@ -2443,7 +2445,11 @@ static int vpfe_probe(struct platform_device *pdev)
>         pm_runtime_enable(&pdev->dev);
>
>         /* for now just enable it here instead of waiting for the open */
> -       pm_runtime_get_sync(&pdev->dev);
> +       ret = pm_runtime_resume_and_get(&pdev->dev);
> +       if (ret < 0) {
> +               vpfe_err(vpfe, "Unable to resume device.\n");
> +               goto probe_out_v4l2_unregister;
> +       }
>
>         vpfe_ccdc_config_defaults(ccdc);
>
> @@ -2530,6 +2536,11 @@ static int vpfe_suspend(struct device *dev)
>
>         /* only do full suspend if streaming has started */
>         if (vb2_start_streaming_called(&vpfe->buffer_queue)) {
> +               /*
> +                * ignore RPM resume errors here, as it is already too late.
> +                * A check like that should happen earlier, either at
> +                * open() or just before start streaming.
> +                */
>                 pm_runtime_get_sync(dev);
>                 vpfe_config_enable(ccdc, 1);
>
> --
> 2.30.2
>