This is a note to let you know that I've just added the patch titled drm/i915/dp: Use max params for panels < eDP 1.4 to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-dp-use-max-params-for-panels-edp-1.4.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From c8dead5751b81dfa6b10449b740ed1062ff670c5 Mon Sep 17 00:00:00 2001 From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> Date: Fri, 20 Aug 2021 15:52:59 +0800 Subject: drm/i915/dp: Use max params for panels < eDP 1.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> commit c8dead5751b81dfa6b10449b740ed1062ff670c5 upstream. 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 Cc: stable@xxxxxxxxxxxxxxx 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.syrjala@xxxxxxxxxxxxxxx> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20210820075301.693099-1-kai.heng.feng@xxxxxxxxxxxxx (cherry picked from commit d7f213c131adf0bec8b731553eb82990cdac265d) Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/display/intel_dp.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -2453,11 +2453,14 @@ intel_edp_init_dpcd(struct intel_dp *int */ 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] Patches currently in stable-queue which might be from kai.heng.feng@xxxxxxxxxxxxx are queue-5.14/drm-i915-dp-use-max-params-for-panels-edp-1.4.patch