linux-kernel - Re: [PATCH] drm/msm/dp: always add fail-safe mode into connector mode list

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Date:   Mon, 24 Jan 2022 13:04:18 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dmitry.baryshkov@...aro.org, robdclark@...il.com, sean@...rly.run,
        vkoul@...nel.org
Cc:     quic_abhinavk@...cinc.com, 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] drm/msm/dp: always add fail-safe mode into connector mode list

Quoting Kuogee Hsieh (2022-01-24 12:46:10)
> Some of DP link compliant test expects to return fail-safe mode
> if prefer detailed timing mode can not be supported by mainlink's
> lane and rate after link training. Therefore add fail-safe mode
> into connector mode list as backup mode. This patch fixes test
> case 4.2.2.1.
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>

Any Fixes tag? I also wonder why this isn't pushed into the DP core code
somehow. Wouldn't every device need to add a 640x480 mode by default?

> ---
>  drivers/gpu/drm/msm/dp/dp_panel.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
> index 3b02922..7743b45 100644
> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> @@ -221,6 +221,11 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
>                 if (drm_add_modes_noedid(connector, 640, 480))
>                         drm_set_preferred_mode(connector, 640, 480);
>                 mutex_unlock(&connector->dev->mode_config.mutex);
> +       } else {
> +               /* always add fail-safe mode as backup mode */
> +               mutex_lock(&connector->dev->mode_config.mutex);
> +               drm_add_modes_noedid(connector, 640, 480);
> +               mutex_unlock(&connector->dev->mode_config.mutex);
>         }
>
>         if (panel->aux_cfg_update_done) {
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>