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From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com,
	rodrigo.vivi@intel.com
Cc: "Kai-Heng Feng" <kai.heng.feng@canonical.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Imre Deak" <imre.deak@intel.com>,
	"Uma Shankar" <uma.shankar@intel.com>,
	"Manasi Navare" <manasi.d.navare@intel.com>,
	"Ankit Nautiyal" <ankit.k.nautiyal@intel.com>,
	"José Roberto de Souza" <jose.souza@intel.com>,
	"Sean Paul" <seanpaul@chromium.org>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3] drm/i915/dp: Use max params for panels < eDP 1.4
Date: Fri, 20 Aug 2021 15:52:59 +0800	[thread overview]
Message-ID: <20210820075301.693099-1-kai.heng.feng@canonical.com> (raw)

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.syrjala@linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@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


             reply	other threads:[~2021-08-20  7:54 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20  7:52 Kai-Heng Feng [this message]
2021-08-20 17:26 ` [PATCH v3] drm/i915/dp: Use max params for panels < eDP 1.4 Ville Syrjälä
2021-08-26 17:37   ` Rodrigo Vivi
2021-08-30 16:42     ` [Intel-gfx] " Rodrigo Vivi

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