The patch below does not apply to the 5.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ab03631087f5c296030dd86265ea02dcdacc6802 Mon Sep 17 00:00:00 2001

From: Imre Deak imre.deak@intel.com Date: Wed, 17 Mar 2021 20:49:01 +0200 Subject: [PATCH] drm/i915: Disable LTTPR support when the LTTPR rev < 1.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

By the specification the 0xF0000 - 0xF02FF range is only valid if the LTTPR revision at 0xF0000 is at least 1.4. Disable the LTTPR support otherwise.

Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training") Cc: stable@vger.kernel.org # v5.11 Cc: Ville Syrjälä ville.syrjala@linux.intel.com Signed-off-by: Imre Deak imre.deak@intel.com Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20210317184901.4029798-4-imre.... (cherry picked from commit 1663ad4936e0679443a315fe342f99636a2420dd) Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index c10e81a3d64f..be6ac0dd846e 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -99,17 +99,23 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp) return false;

if (drm_dp_read_lttpr_common_caps(&intel_dp->aux, - intel_dp->lttpr_common_caps) < 0) { - intel_dp_reset_lttpr_common_caps(intel_dp); - return false; - } + intel_dp->lttpr_common_caps) < 0) + goto reset_caps;

drm_dbg_kms(&dp_to_i915(intel_dp)->drm, "LTTPR common capabilities: %*ph\n", (int)sizeof(intel_dp->lttpr_common_caps), intel_dp->lttpr_common_caps);

+ /* The minimum value of LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV is 1.4 */ + if (intel_dp->lttpr_common_caps[0] < 0x14) + goto reset_caps; + return true; + +reset_caps: + intel_dp_reset_lttpr_common_caps(intel_dp); + return false; }

static bool