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 C9735C433F5 for ; Mon, 10 Oct 2022 07:15:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232289AbiJJHPq (ORCPT ); Mon, 10 Oct 2022 03:15:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232210AbiJJHNn (ORCPT ); Mon, 10 Oct 2022 03:13:43 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC1945F200; Mon, 10 Oct 2022 00:08:57 -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 ams.source.kernel.org (Postfix) with ESMTPS id 5C1A5B80E69; Mon, 10 Oct 2022 07:08:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7FCFC433D6; Mon, 10 Oct 2022 07:08:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1665385736; bh=HfLz4j7DE39PIpdF5+dXZg8UWtbplrHysO5ptm/cBFE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tH8W36jQ5G3RhTcFhBaID7s1QVBEcu1YNZJ0BrUdLdNjp9Y+650RjnIjhoEFC6IZJ lOIuDNP89AtuMgRoObZG02I7ThaACngTiYaL1P2uOruM8CMlnx7viXeC0YenHceEWf VA3Ms6o0DNWXqqhExz4RJGbTQXbaoqrRrp8Flg0o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, George Shen , Wayne Lin , Michael Strauss , Daniel Wheeler , Alex Deucher , Sasha Levin Subject: [PATCH 5.15 25/37] drm/amd/display: Assume an LTTPR is always present on fixed_vs links Date: Mon, 10 Oct 2022 09:05:44 +0200 Message-Id: <20221010070331.941157714@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221010070331.211113813@linuxfoundation.org> References: <20221010070331.211113813@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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