From: Ville Syrjälä ville.syrjala@linux.intel.com
[ Upstream commit 2682768bde745b10ae126a322cdcaf532cf88851 ]
There are some weird EDIDs floating around that have the sync pulse extending beyond the end of the blanking period.
On the currently problemtic machine (HP Omni 120) EDID reports the following mode: "1600x900": 60 108000 1600 1780 1860 1800 900 910 913 1000 0x40 0x5 which is then "corrected" to have htotal=1861 by the current drm_edid.c code.
The fixup code was originally added in commit 7064fef56369 ("drm: work around EDIDs with bad htotal/vtotal values"). Googling around we end up in https://bugs.launchpad.net/ubuntu/hardy/+source/xserver-xorg-video-intel/+bu... where we find an EDID for a Dell Studio 15, which reports: (II) VESA(0): clock: 65.0 MHz Image Size: 331 x 207 mm (II) VESA(0): h_active: 1280 h_sync: 1328 h_sync_end 1360 h_blank_end 1337 h_border: 0 (II) VESA(0): v_active: 800 v_sync: 803 v_sync_end 809 v_blanking: 810 v_border: 0
Note that if we use the hblank size (as opposed of the hsync_end) from the DTD to determine htotal we get exactly 60Hz refresh rate in both cases, whereas using hsync_end to determine htotal we get a slightly lower refresh rates. This makes me believe the using the hblank size is what was intended even in those cases.
Also note that in case of the HP Onmi 120 the VBIOS boots with these: crtc timings: 108000 1600 1780 1860 1800 900 910 913 1000, type: 0x40 flags: 0x5 ie. it just blindly stuffs the bogus hsync_end and htotal from the DTD into the transcoder timing registers, and the display works. I believe the (at least more modern) hardware will automagically terminate the hsync pulse when the timing generator reaches htotal, which again points that we should use the hblank size to determine htotal. Unfortunatley the old bug reports for the Dell machines are extremely lacking in useful details so we have no idea what kind of timings the VBIOS programmed into the hardware :(
Let's just flip this quirk around and reduce the length of the sync pulse instead of extending the blanking period. This at least seems to be the correct thing to do on more modern hardware. And if any issues crop up on older hardware we need to debug them properly.
v2: Add debug message breadcrumbs (Jani)
Reviewed-by: Jani Nikula jani.nikula@intel.com Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8895 Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20230920211934.14920-1-ville.s... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/drm_edid.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 69d855123d3e3..f1ceb7d08519e 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -3499,11 +3499,19 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_connector *connecto mode->vsync_end = mode->vsync_start + vsync_pulse_width; mode->vtotal = mode->vdisplay + vblank;
- /* Some EDIDs have bogus h/vtotal values */ - if (mode->hsync_end > mode->htotal) - mode->htotal = mode->hsync_end + 1; - if (mode->vsync_end > mode->vtotal) - mode->vtotal = mode->vsync_end + 1; + /* Some EDIDs have bogus h/vsync_end values */ + if (mode->hsync_end > mode->htotal) { + drm_dbg_kms(dev, "[CONNECTOR:%d:%s] reducing hsync_end %d->%d\n", + connector->base.id, connector->name, + mode->hsync_end, mode->htotal); + mode->hsync_end = mode->htotal; + } + if (mode->vsync_end > mode->vtotal) { + drm_dbg_kms(dev, "[CONNECTOR:%d:%s] reducing vsync_end %d->%d\n", + connector->base.id, connector->name, + mode->vsync_end, mode->vtotal); + mode->vsync_end = mode->vtotal; + }
drm_mode_do_interlace_quirk(mode, pt);