Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use
fast+narrow link on eDP again and fall back to the old max strategy on
failure"), the screen starts to have wobbly effect.
Commit a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
everything") doesn't help either, that means the affected eDP 1.2 panels
only work with max params.
So use max params for panels < eDP 1.4 as Windows does to solve the
issue.
v3:
- Do the eDP rev check in intel_edp_init_dpcd()
v2:
- Check eDP 1.4 instead of DPCD 1.1 to apply max params
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3714
Fixes: 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and
fall back to the old max strategy on failure")
Fixes: a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
everything")
Suggested-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.f...@canonical.com>
---
drivers/gpu/drm/i915/display/intel_dp.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
b/drivers/gpu/drm/i915/display/intel_dp.c
index 75d4ebc669411..e0dbd35ae7bc0 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2445,11 +2445,14 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
*/
if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
- sizeof(intel_dp->edp_dpcd))
+ sizeof(intel_dp->edp_dpcd)) {
drm_dbg_kms(&dev_priv->drm, "eDP DPCD: %*ph\n",
(int)sizeof(intel_dp->edp_dpcd),
intel_dp->edp_dpcd);
+ intel_dp->use_max_params = intel_dp->edp_dpcd[0] < DP_EDP_14;
+ }
+
/*
* This has to be called after intel_dp->edp_dpcd is filled, PSR checks
* for SET_POWER_CAPABLE bit in intel_dp->edp_dpcd[1]
--
2.32.0
