On Sun, May 31, 2026 at 11:16:51PM +0200, Jens Glathe via B4 Relay wrote: > From: Jens Glathe <[email protected]> > > drm_edid_read_ddc() can return a structurally valid EDID from which
When? > drm_edid_connector_add_modes() still returns zero modes. This triggers > the error: Please at least add EDID contents. > > [drm:msm_dp_bridge_get_modes [msm]] *ERROR* failed to get DP sink > modes, rc=0 > > even though the link is ready. Since the EDID is only read once, this > error persists and the display comes up with 640x480 resolution. Please check with the current next tree, we have reworked HPD handling a bit. Also, it might be the case that the dongle sends a placeholder first and then sends a HPD or IRQ_HPD event. Please check if that's the case. > > Add a retry of drm_edid_read_ddc() inside get_modes() when the initial > read produces no usable modes. The bad EDID is freed before retrying > and container_of ensures access to the DDC channel. This directly > addresses the observed "valid but empty/garbage" EDID case on > flaky DP plugs and adapters. > > I tested this on a few of my "flaky" type-c to HDMI adapters and hubs, > getting no "retry failed" messages and the desired resolution. Without > the patch most plugs would result in 640x480 external display. > > Fixes: [5bea90ad9743d2] "drm/msm/dp: switch to struct drm_edid" Hard to believe. > > Signed-off-by: Jens Glathe <[email protected]> > --- > drivers/gpu/drm/msm/dp/dp_panel.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > -- With best wishes Dmitry
