linux-kernel - Re: [PATCH] drm/edid: add a quirk for two 240Hz Samsung monitors

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Message-ID: <CADnq5_Nv0MnG+pPvRQO37OP8iYwz8oGvFLs2g-+U=URHWcqJGw@mail.gmail.com>
Date:   Wed, 1 Nov 2023 17:36:24 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Hamza Mahfooz <hamza.mahfooz@....com>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>,
        amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Jerry Zuo <jerry.zuo@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH] drm/edid: add a quirk for two 240Hz Samsung monitors

On Wed, Nov 1, 2023 at 5:01 PM Hamza Mahfooz <hamza.mahfooz@....com> wrote:
>
> Without this fix the 5120x1440@240 timing of these monitors
> leads to screen flickering.
>
> Cc: stable@...r.kernel.org # 6.1+
> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1442
> Co-developed-by: Harry Wentland <harry.wentland@....com>
> Signed-off-by: Harry Wentland <harry.wentland@....com>
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
> ---
>  drivers/gpu/drm/drm_edid.c | 47 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 44 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index bca2af4fe1fc..3fdb8907f66b 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -89,6 +89,8 @@ static int oui(u8 first, u8 second, u8 third)
>  #define EDID_QUIRK_NON_DESKTOP                 (1 << 12)
>  /* Cap the DSC target bitrate to 15bpp */
>  #define EDID_QUIRK_CAP_DSC_15BPP               (1 << 13)
> +/* Fix up a particular 5120x1440@...Hz timing */
> +#define EDID_QUIRK_FIXUP_5120_1440_240         (1 << 14)

What is wrong with the original timing that needs to be fixed?

Alex


>
>  #define MICROSOFT_IEEE_OUI     0xca125c
>
> @@ -170,6 +172,12 @@ static const struct edid_quirk {
>         EDID_QUIRK('S', 'A', 'M', 596, EDID_QUIRK_PREFER_LARGE_60),
>         EDID_QUIRK('S', 'A', 'M', 638, EDID_QUIRK_PREFER_LARGE_60),
>
> +       /* Samsung C49G95T */
> +       EDID_QUIRK('S', 'A', 'M', 0x7053, EDID_QUIRK_FIXUP_5120_1440_240),
> +
> +       /* Samsung S49AG95 */
> +       EDID_QUIRK('S', 'A', 'M', 0x71ac, EDID_QUIRK_FIXUP_5120_1440_240),
> +
>         /* Sony PVM-2541A does up to 12 bpc, but only reports max 8 bpc */
>         EDID_QUIRK('S', 'N', 'Y', 0x2541, EDID_QUIRK_FORCE_12BPC),
>
> @@ -6586,7 +6594,37 @@ static void update_display_info(struct drm_connector *connector,
>         drm_edid_to_eld(connector, drm_edid);
>  }
>
> -static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *dev,
> +static void drm_mode_displayid_detailed_edid_quirks(struct drm_connector *connector,
> +                                                   struct drm_display_mode *mode)
> +{
> +       unsigned int hsync_width;
> +       unsigned int vsync_width;
> +
> +       if (connector->display_info.quirks & EDID_QUIRK_FIXUP_5120_1440_240) {
> +               if (mode->hdisplay == 5120 && mode->vdisplay == 1440 &&
> +                   mode->clock == 1939490) {
> +                       hsync_width = mode->hsync_end - mode->hsync_start;
> +                       vsync_width = mode->vsync_end - mode->vsync_start;
> +
> +                       mode->clock = 2018490;
> +                       mode->hdisplay = 5120;
> +                       mode->hsync_start = 5120 + 8;
> +                       mode->hsync_end = 5120 + 8 + hsync_width;
> +                       mode->htotal = 5200;
> +
> +                       mode->vdisplay = 1440;
> +                       mode->vsync_start = 1440 + 165;
> +                       mode->vsync_end = 1440 + 165 + vsync_width;
> +                       mode->vtotal = 1619;
> +
> +                       drm_dbg_kms(connector->dev,
> +                                   "[CONNECTOR:%d:%s] Samsung 240Hz mode quirk applied\n",
> +                                   connector->base.id, connector->name);
> +               }
> +       }
> +}
> +
> +static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_connector *connector,
>                                                             struct displayid_detailed_timings_1 *timings,
>                                                             bool type_7)
>  {
> @@ -6605,7 +6643,7 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
>         bool hsync_positive = (timings->hsync[1] >> 7) & 0x1;
>         bool vsync_positive = (timings->vsync[1] >> 7) & 0x1;
>
> -       mode = drm_mode_create(dev);
> +       mode = drm_mode_create(connector->dev);
>         if (!mode)
>                 return NULL;
>
> @@ -6628,6 +6666,9 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
>
>         if (timings->flags & 0x80)
>                 mode->type |= DRM_MODE_TYPE_PREFERRED;
> +
> +       drm_mode_displayid_detailed_edid_quirks(connector, mode);
> +
>         drm_mode_set_name(mode);
>
>         return mode;
> @@ -6650,7 +6691,7 @@ static int add_displayid_detailed_1_modes(struct drm_connector *connector,
>         for (i = 0; i < num_timings; i++) {
>                 struct displayid_detailed_timings_1 *timings = &det->timings[i];
>
> -               newmode = drm_mode_displayid_detailed(connector->dev, timings, type_7);
> +               newmode = drm_mode_displayid_detailed(connector, timings, type_7);
>                 if (!newmode)
>                         continue;
>
> --
> 2.42.0
>