From mboxrd@z Thu Jan 1 00:00:00 1970 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 27E17C433F5 for ; Sun, 2 Oct 2022 22:55:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230399AbiJBWzw (ORCPT ); Sun, 2 Oct 2022 18:55:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230356AbiJBWzA (ORCPT ); Sun, 2 Oct 2022 18:55:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA4013E770; Sun, 2 Oct 2022 15:51:46 -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 EE53C60F23; Sun, 2 Oct 2022 22:51:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44144C433C1; Sun, 2 Oct 2022 22:51:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664751105; bh=HfLz4j7DE39PIpdF5+dXZg8UWtbplrHysO5ptm/cBFE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uOD8SV4PYbVY5tOOpSyAQQ1Atcr2E+4/UFL68yPUcAdd2DuJcpOBITGUVjYbnHDNN uGfyjMPTMt3tJo0mkh8gK8eL4AFhXFiD5MNdzaB0mSOADNIiscIWp7ZbaMFt5RNNN1 jclRJP36dluwZ4ndftryc4zi+IgdK9GBeiSKPFEgN6fpuylP7loq6g+YscPfehtlWp rG/4kjt2xHEyuj0nQImt9KEDR24H4ZzDpi4UrThhnYINLj7pAigGG7OEG9CzTPZr0o XMt4s/qCHZ8Sv8fx+UvroycvHFdr5GU+ocbuHdjNQ5MfzHIgfDfPjWW0ck0zACXkOe POWk24VhCk5nQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Michael Strauss , George Shen , Wayne Lin , Daniel Wheeler , Alex Deucher , Sasha Levin , harry.wentland@amd.com, sunpeng.li@amd.com, Rodrigo.Siqueira@amd.com, christian.koenig@amd.com, Xinhui.Pan@amd.com, airlied@gmail.com, daniel@ffwll.ch, wenjing.liu@amd.com, george.shen@amd.com, Jun.Lei@amd.com, Jimmy.Kizito@amd.com, mikita.lipski@amd.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH AUTOSEL 5.15 18/20] drm/amd/display: Assume an LTTPR is always present on fixed_vs links Date: Sun, 2 Oct 2022 18:50:57 -0400 Message-Id: <20221002225100.239217-18-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221002225100.239217-1-sashal@kernel.org> References: <20221002225100.239217-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michael Strauss [ Upstream commit 29956d0fded036a570bd8e7d4ea4b1a1730307d2 ] [WHY] LTTPRs can in very rare instsances fail to increment DPCD LTTPR count. This results in aux-i LTTPR requests to be sent to the wrong DPCD address, which causes link training failure. [HOW] Override internal repeater count if fixed_vs flag is set for a given link Reviewed-by: George Shen Acked-by: Wayne Lin Signed-off-by: Michael Strauss Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c index 6d5dc5ab3d8c..a6ff1b17fd22 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c @@ -3703,6 +3703,14 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link) lttpr_dpcd_data[DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT - DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV]; + /* If this chip cap is set, at least one retimer must exist in the chain + * Override count to 1 if we receive a known bad count (0 or an invalid value) */ + if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN && + (dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) == 0)) { + ASSERT(0); + link->dpcd_caps.lttpr_caps.phy_repeater_cnt = 0x80; + } + /* Attempt to train in LTTPR transparent mode if repeater count exceeds 8. */ is_lttpr_present = (dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) != 0 && link->dpcd_caps.lttpr_caps.max_lane_count > 0 && -- 2.35.1