linux-kernel - Re: [PATCH v2] drm/msm/dp: update is_connected status base on sink count at dp_pm

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Message-ID: <CAE-0n51qc7LX-hWiFEGWRAZqNUgQAQ3XCxO6oEYWZh7wvkxs5Q@mail.gmail.com>
Date:   Tue, 3 Aug 2021 01:55:25 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>, agross@...nel.org,
        bjorn.andersson@...aro.org, robdclark@...il.com, sean@...rly.run,
        vkoul@...nel.org
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dp: update is_connected status base on sink
 count at dp_pm_resume()

Quoting Kuogee Hsieh (2021-08-02 13:20:55)
> Currently at dp_pm_resume() is_connected state is decided base on hpd connection
> status only. This will put is_connected in wrongly "true" state at the scenario
> that dongle attached to DUT but without hmdi cable connecting to it. Fix this
> problem by adding read sink count from dongle and decided is_connected state base
> on both sink count and hpd connection status.
>
> Changes in v2:
> -- remove dp_get_sink_count() cand call drm_dp_read_sink_count()
>
> Fixes: d9aa6571b28ba ("drm/msm/dp: check sink_count before update is_connected status")
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 8b69114..6dcb78e 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1403,6 +1403,7 @@ static int dp_pm_resume(struct device *dev)
>         struct msm_dp *dp_display = platform_get_drvdata(pdev);
>         struct dp_display_private *dp;
>         u32 status;

'status' is unused now, right? The compiler should be complaining about
unused local variables.

> +       int sink_count = 0;
>
>         dp = container_of(dp_display, struct dp_display_private, dp_display);
>  xlog(__func__, 1,0,0, dp->core_initialized, dp_display->power_on);
> @@ -1417,15 +1418,26 @@ xlog(__func__, 1,0,0, dp->core_initialized, dp_display->power_on);
>
>         dp_catalog_ctrl_hpd_config(dp->catalog);
>
> -       status = dp_catalog_link_is_connected(dp->catalog);
> +       /*
> +        * set sink to normal operation mode -- D0
> +        * before dpcd read
> +        */
> +       dp_link_psm_config(dp->link, &dp->panel->link_info, false);
> +
> +       /* if sink conencted, do dpcd read sink count */
> +       if ((status = dp_catalog_link_is_connected(dp->catalog))) {
> +               sink_count = drm_dp_read_sink_count(dp->aux);
> +               if (sink_count < 0)
> +                       sink_count = 0;
> +       }
>
> +       dp->link->sink_count = sink_count;
>         /*
>          * can not declared display is connected unless
>          * HDMI cable is plugged in and sink_count of
>          * dongle become 1
>          */
> -xlog(__func__, 0x12,0,0, 0, dp->link->sink_count);
> -       if (status && dp->link->sink_count)
> +       if (dp->link->sink_count)
>                 dp->dp_display.is_connected = true;
>         else
>                 dp->dp_display.is_connected = false;