From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACD8F15990C for ; Thu, 21 Aug 2025 14:36:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755786980; cv=none; b=PSEcRv337XC1ZTz3di9l5QwazGUVOpL728zPeF8Uy41O++UgjjAXyV8L+Lvcj1JoXx7+MsW1NVs8ER4i6YECJ1jHsZA0S9y7D4MLZ2uAELQUfaMFy6TooU+TWY4t0LeU3x3o3y4fZDvAc62thDN9t1dP3ZXFwgQYg2piRGinJs4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755786980; c=relaxed/simple; bh=LUH52tmXzyetDNdjA9dXsrHBKSYfhAn6pJ+emQAhEto=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=KgucorkHd4CW7BNojqtB/NPOM8OOCUASnKY8Al2Arg/M0s4TiUrCto10RS9oc8424McxxZVdPBX02k2cIIbKaYlbokW6LjaGC/clSnqimUCx+BQUIiCJ4e1i168sh6Muu0wu2pCjLe+19ZLtlD3dcqKV61AGyLHBdbYcjg39ik4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cNmVDey4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="cNmVDey4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 17DBEC4CEED; Thu, 21 Aug 2025 14:36:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755786980; bh=LUH52tmXzyetDNdjA9dXsrHBKSYfhAn6pJ+emQAhEto=; h=Subject:To:Cc:From:Date:From; b=cNmVDey4B4U23ER3vLHYkDgdEg+m6QxzqWPG0TqikEkTklC2MAIOHBIDsiua/Olz2 DHV3fw0wcNk+hIbu2mB41BDEmlXqlk2rYFeRWIl8Locfvb+tSAEdSjTOhgg8cmsKxT BmcpzibD0k6Xn+vlWYcHMS3Q89JBICCg0kjBv7Ew= Subject: FAILED: patch "[PATCH] drm/dp: Change AUX DPCD probe address from DPCD_REV to" failed to apply to 5.15-stable tree To: imre.deak@intel.com,jani.nikula@intel.com,jani.nikula@linux.intel.com,stable@vger.kernel.org,ville.syrjala@linux.intel.com Cc: From: Date: Thu, 21 Aug 2025 16:35:51 +0200 Message-ID: <2025082151-chase-quilt-9ad4@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x a40c5d727b8111b5db424a1e43e14a1dcce1e77f # git commit -s git send-email --to '' --in-reply-to '2025082151-chase-quilt-9ad4@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a40c5d727b8111b5db424a1e43e14a1dcce1e77f Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Thu, 5 Jun 2025 11:28:46 +0300 Subject: [PATCH] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Reading DPCD registers has side-effects in general. In particular accessing registers outside of the link training register range (0x102-0x106, 0x202-0x207, 0x200c-0x200f, 0x2216) is explicitly forbidden by the DP v2.1 Standard, see 3.6.5.1 DPTX AUX Transaction Handling Mandates 3.6.7.4 128b/132b DP Link Layer LTTPR Link Training Mandates Based on my tests, accessing the DPCD_REV register during the link training of an UHBR TBT DP tunnel sink leads to link training failures. Solve the above by using the DP_LANE0_1_STATUS (0x202) register for the DPCD register access quirk. Cc: Cc: Ville Syrjälä Cc: Jani Nikula Acked-by: Jani Nikula Signed-off-by: Imre Deak Link: https://lore.kernel.org/r/20250605082850.65136-2-imre.deak@intel.com diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index f2a6559a2710..dc622c78db9d 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -725,7 +725,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, * monitor doesn't power down exactly after the throw away read. */ if (!aux->is_remote) { - ret = drm_dp_dpcd_probe(aux, DP_DPCD_REV); + ret = drm_dp_dpcd_probe(aux, DP_LANE0_1_STATUS); if (ret < 0) return ret; }