linux-kernel - Re: [PATCH 5/7] drm/msm/dp: return correct edid checksum after corrupted edid checksum read

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Message-ID: <CAE-0n53BnbjD3QaZ5vynJxw44ANatvvRW3rqytyG4jvjKs7L_g@mail.gmail.com>
Date:   Thu, 8 Jul 2021 07:14:31 +0000
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>,
        dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org, airlied@...ux.ie,
        daniel@...ll.ch, bjorn.andersson@...aro.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] drm/msm/dp: return correct edid checksum after
 corrupted edid checksum read

Quoting Kuogee Hsieh (2021-07-06 10:20:18)
> Response with correct edid checksum saved at connector after corrupted edid
> checksum read. This fixes Link Layer CTS cases 4.2.2.3, 4.2.2.6.
>
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_panel.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
> index 88196f7..0fdb551 100644
> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> @@ -271,7 +271,7 @@ static u8 dp_panel_get_edid_checksum(struct edid *edid)
>  {
>         struct edid *last_block;
>         u8 *raw_edid;
> -       bool is_edid_corrupt;
> +       bool is_edid_corrupt = false;
>
>         if (!edid) {
>                 DRM_ERROR("invalid edid input\n");
> @@ -303,7 +303,12 @@ void dp_panel_handle_sink_request(struct dp_panel *dp_panel)
>         panel = container_of(dp_panel, struct dp_panel_private, dp_panel);
>
>         if (panel->link->sink_request & DP_TEST_LINK_EDID_READ) {
> -               u8 checksum = dp_panel_get_edid_checksum(dp_panel->edid);
> +               u8 checksum;
> +
> +               if (dp_panel->edid)
> +                       checksum = dp_panel_get_edid_checksum(dp_panel->edid);
> +               else
> +                       checksum = dp_panel->connector->real_edid_checksum;
>
>                 dp_link_send_edid_checksum(panel->link, checksum);

It looks like this can be drm_dp_send_real_edid_checksum()? Then we
don't have to look at the connector internals sometimes and can drop
dp_panel_get_edid_checksum() entirely?

>                 dp_link_send_test_response(panel->link);