+++ /dev/null
-From 672d6ca758651f0ec12cd0d59787067a5bde1c96 Mon Sep 17 00:00:00 2001
-From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
-Date: Fri, 2 Sep 2022 10:03:18 +0300
-Subject: drm/i915: Implement WaEdpLinkRateDataReload
-MIME-Version: 1.0
-Content-Type: text/plain; charset=UTF-8
-Content-Transfer-Encoding: 8bit
-
-From: Ville Syrjälä <ville.syrjala@linux.intel.com>
-
-commit 672d6ca758651f0ec12cd0d59787067a5bde1c96 upstream.
-
-A lot of modern laptops use the Parade PS8461E MUX for eDP
-switching. The MUX can operate in jitter cleaning mode or
-redriver mode, the first one resulting in higher link
-quality. The jitter cleaning mode needs to know the link
-rate used and the MUX achieves this by snooping the
-LINK_BW_SET, LINK_RATE_SELECT and SUPPORTED_LINK_RATES
-DPCD accesses.
-
-When the MUX is powered down (seems this can happen whenever
-the display is turned off) it loses track of the snooped
-link rates so when we do the LINK_RATE_SELECT write it no
-longer knowns which link rate we're selecting, and thus it
-falls back to the lower quality redriver mode. This results
-in unstable high link rates (eg. usually 8.1Gbps link rate
-no longer works correctly).
-
-In order to avoid all that let's re-snoop SUPPORTED_LINK_RATES
-from the sink at the start of every link training.
-
-Unfortunately we don't have a way to detect the presence of
-the MUX. It looks like the set of laptops equipped with this
-MUX is fairly large and contains devices from multiple
-manufacturers. It may also still be growing with new models.
-So a quirk doesn't seem like a very easily maintainable
-option, thus we shall attempt to do this unconditionally on
-all machines that use LINK_RATE_SELECT. Hopefully this extra
-DPCD read doesn't cause issues for any unaffected machine.
-If that turns out to be the case we'll need to convert this
-into a quirk in the future.
-
-Cc: stable@vger.kernel.org
-Cc: Jason A. Donenfeld <Jason@zx2c4.com>
-Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
-Cc: Jani Nikula <jani.nikula@intel.com>
-Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6205
-Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
-Link: https://patchwork.freedesktop.org/patch/msgid/20220902070319.15395-1-ville.syrjala@linux.intel.com
-Tested-by: Aaron Ma <aaron.ma@canonical.com>
-Tested-by: Jason A. Donenfeld <Jason@zx2c4.com>
-Reviewed-by: Jani Nikula <jani.nikula@intel.com>
-(cherry picked from commit 25899c590cb5ba9b9f284c6ca8e7e9086793d641)
-Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
----
- drivers/gpu/drm/i915/display/intel_dp_link_training.c | 22 ++++++++++++++++++
- 1 file changed, 22 insertions(+)
-
---- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
-+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
-@@ -142,6 +142,28 @@ intel_dp_link_training_clock_recovery(st
- intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
- &link_bw, &rate_select);
-
-+ /*
-+ * WaEdpLinkRateDataReload
-+ *
-+ * Parade PS8461E MUX (used on varius TGL+ laptops) needs
-+ * to snoop the link rates reported by the sink when we
-+ * use LINK_RATE_SET in order to operate in jitter cleaning
-+ * mode (as opposed to redriver mode). Unfortunately it
-+ * loses track of the snooped link rates when powered down,
-+ * so we need to make it re-snoop often. Without this high
-+ * link rates are not stable.
-+ */
-+ if (!link_bw) {
-+ struct intel_connector *connector = intel_dp->attached_connector;
-+ __le16 sink_rates[DP_MAX_SUPPORTED_RATES];
-+
-+ drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Reloading eDP link rates\n",
-+ connector->base.base.id, connector->base.name);
-+
-+ drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES,
-+ sink_rates, sizeof(sink_rates));
-+ }
-+
- if (link_bw)
- DRM_DEBUG_KMS("Using LINK_BW_SET value %02x\n", link_bw);
- else
projects / thirdparty / kernel / stable-queue.git / commitdiff
