From nobody Mon Apr 6 00:08:13 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B2C2C54EE9 for ; Tue, 13 Sep 2022 15:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235176AbiIMPHI (ORCPT ); Tue, 13 Sep 2022 11:07:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235478AbiIMPEg (ORCPT ); Tue, 13 Sep 2022 11:04:36 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EB1B74DCE; Tue, 13 Sep 2022 07:30:21 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BAC3A614B6; Tue, 13 Sep 2022 14:23:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D17D1C433C1; Tue, 13 Sep 2022 14:23:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663079030; bh=qw+AuVF2vbBLzKv6kIt8ab6sjz0MEMRHaxZ7VPhNNuY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DstIEtFGNLungn9m7u03YUUy9l7vbu/sM6NYMQ8KOwA9M9JCccssEWa9jh+f16r+l yB5sJwaOGWhGL5ltyz9JssDQfnOmoa0dzn+WxQ14ixySDZxodfqWuiq76dST39qJeu ygTHnW/zjyjxnu8Wn5LPfzbBjugNXG835M8hSrvs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Jason A. Donenfeld" , Ankit Nautiyal , Jani Nikula , =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Aaron Ma , Rodrigo Vivi Subject: [PATCH 5.10 30/79] drm/i915: Implement WaEdpLinkRateDataReload Date: Tue, 13 Sep 2022 16:04:35 +0200 Message-Id: <20220913140351.757713465@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140350.291927556@linuxfoundation.org> References: <20220913140350.291927556@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ville Syrj=C3=A4l=C3=A4 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 Cc: Ankit Nautiyal Cc: Jani Nikula Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6205 Signed-off-by: Ville Syrj=C3=A4l=C3=A4 Link: https://patchwork.freedesktop.org/patch/msgid/20220902070319.15395-1-= ville.syrjala@linux.intel.com Tested-by: Aaron Ma Tested-by: Jason A. Donenfeld Reviewed-by: Jani Nikula (cherry picked from commit 25899c590cb5ba9b9f284c6ca8e7e9086793d641) Signed-off-by: Rodrigo Vivi Signed-off-by: Greg Kroah-Hartman --- 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 @@ -163,6 +163,28 @@ intel_dp_link_training_clock_recovery(st intel_dp_compute_rate(intel_dp, intel_dp->link_rate, &link_bw, &rate_select); =20 + /* + * 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 =3D 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_dbg_kms(&i915->drm, "Using LINK_BW_SET value %02x\n", link_bw);