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

[Hamza Mahfooz <hamza.mahfooz@xxxxxxx>]

On 11/1/23 17:36, Alex Deucher wrote:
> On Wed, Nov 1, 2023 at 5:01 PM Hamza Mahfooz <hamza.mahfooz@xxxxxxx> wrote:
> > Without this fix the 5120x1440@240 timing of these monitors
> > leads to screen flickering.
> >
> > Cc: stable@xxxxxxxxxxxxxxx # 6.1+
> > Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1442
> > Co-developed-by: Harry Wentland <harry.wentland@xxxxxxx>
> > Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
> > Signed-off-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> > ---
> >   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@240Hz timing */
> > +#define EDID_QUIRK_FIXUP_5120_1440_240         (1 << 14)
>
> What is wrong with the original timing that needs to be fixed?

Apparently, all of timing values for the 5120x1440@240 mode of these
monitors aren't set correctly (they are all lower than they should be)
in their EDIDs. For what it's worth, the windows driver has had a quirk
similar the one proposed in this patch for ~2 years.

> 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
--
Hamza