From patchwork Sat Sep 10 00:16:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Aaron Ma X-Patchwork-Id: 1676314 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=canonical.com header.i=@canonical.com header.a=rsa-sha256 header.s=20210705 header.b=tWiwjJuR; dkim-atps=neutral Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4MPYMg33Bmz1ypD for ; Sat, 10 Sep 2022 10:17:16 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1oWoBJ-0001lT-NY; Sat, 10 Sep 2022 00:17:09 +0000 Received: from smtp-relay-canonical-1.internal ([10.131.114.174] helo=smtp-relay-canonical-1.canonical.com) by huckleberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1oWoBE-0001hN-GH for kernel-team@lists.ubuntu.com; Sat, 10 Sep 2022 00:17:04 +0000 Received: from localhost.localdomain (unknown [222.129.34.149]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-canonical-1.canonical.com (Postfix) with ESMTPSA id 2967D42978 for ; Sat, 10 Sep 2022 00:17:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1662769024; bh=ysarF8wrhiPE54NfMvdL+cSKoJxfk6F2RP6DjaRjkQ4=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=tWiwjJuRdvZws4TZkgGD5aVht/qYQT292h57uyzCPMIKBIISg63EE+Pl/WWeWCES6 Drks7e7pAxI7qnOmH2SN+aW+Vea63dawJE0UASGwfJtVe0gL1viPlsUKJQTvLgsdDZ 7DfIr3uaRt7Od3jtQhKKWuW22ifOFtskDvrg8t27CLZSI+3P0UulteZhsGGJRHQr1T P2BrAeVmOfL1fIBiYxmCtOf8i83SpCr+idllPUBXkqiW53OyxTXXR8ensnQRZDWZHZ 0ZEdWqxy2KANOx4A/QPmTVyurF6G4x/KEcHVptlkGvTK3eXQz5NyC6F1mqmOL7eboj TeN3sGUv7HPGg== From: Aaron Ma To: kernel-team@lists.ubuntu.com Subject: [PATCH 1/2][J/OEM-5.17/K/U] UBUNTU: SAUCE: drm/i915: Implement WaEdpLinkRateDataReload Date: Sat, 10 Sep 2022 08:16:54 +0800 Message-Id: <20220910001655.13487-2-aaron.ma@canonical.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220910001655.13487-1-aaron.ma@canonical.com> References: <20220910001655.13487-1-aaron.ma@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Ville Syrjälä BugLink: https://bugs.launchpad.net/bugs/1980621 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 Syrjälä 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 https://anongit.freedesktop.org/git/drm-intel.git drm-intel-next) Signed-off-by: Aaron Ma --- .../drm/i915/display/intel_dp_link_training.c | 22 +++++++++++++++++++ 1 file changed, 22 insertions(+) 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 9feaf1a589f3..d213d8ad1ea5 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -671,6 +671,28 @@ intel_dp_prepare_link_train(struct intel_dp *intel_dp, intel_dp_compute_rate(intel_dp, crtc_state->port_clock, &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_dbg_kms(&i915->drm, "[ENCODER:%d:%s] Using LINK_BW_SET value %02x\n",