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

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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




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