linux-kernel - Re: [PATCH v4 2/2] drm/msm/dp: retry 3 times if set sink to D0 poweer state failed

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Message-ID: <CAA8EJpoEPD7pvLcCOnH-r-J=zVxm5C=ZOvMYLBqfwv4ufSWmDA@mail.gmail.com>
Date:   Fri, 9 Sep 2022 01:10:14 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org,
        quic_abhinavk@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] drm/msm/dp: retry 3 times if set sink to D0 poweer
 state failed

On Fri, 9 Sept 2022 at 00:18, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>
> Bring sink out of D3 (power down) mode into D0 (normal operation) mode
> by setting DP_SET_POWER_D0 bit to DP_SET_POWER dpcd register. This
> patch will retry 3 times if written to DP_SET_POWER register failed.
>
> Changes in v4:
> -- split into two patches
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_link.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c
> index 36f0af0..7b5ecf5 100644
> --- a/drivers/gpu/drm/msm/dp/dp_link.c
> +++ b/drivers/gpu/drm/msm/dp/dp_link.c
> @@ -49,23 +49,26 @@ static int dp_aux_link_power_up(struct drm_dp_aux *aux,
>                                         struct dp_link_info *link)
>  {
>         u8 value;
> -       int err;
> +       ssize_t len;
> +       int i;
>
>         if (link->revision < 0x11)
>                 return 0;
>
> -       err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> -       if (err < 0)
> -               return err;
> +       len = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> +       if (len < 0)
> +               return len;

This is a separate patch.

>
>         value &= ~DP_SET_POWER_MASK;
>         value |= DP_SET_POWER_D0;
>
> -       err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> -       if (err < 0)
> -               return err;
> -
> -       usleep_range(1000, 2000);
> +       /* retry for 1ms to give the sink time to wake up */
> +       for (i = 0; i < 3; i++) {
> +               len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> +               usleep_range(1000, 2000);
> +               if (len == 1)
> +                       break;
> +       }
>
>         return 0;
>  }
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>


-- 
With best wishes
Dmitry