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

[Jani Nikula <jani.nikula@linux.intel.com>]

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

Indeed. I'd be wary of applying this quirk as-is, because it'll impact
all drivers and all connectors.

The bug report does not have a single EDID from the affected displays
attached.

The quirk sets mode members that apparently do not need to be modified.

Cc: Ville


BR,
Jani.


>
> 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
>>

-- 
Jani Nikula, Intel