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 0AD0B34DCF6; Tue, 26 Aug 2025 14:02:05 +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=1756216925; cv=none; b=JVw2NsNwInLP3YM+FJ5UpwHQbUfoYXu4RtHGiSX8xxyyROjiZPN6LCh7HvHZdkstMFM9JHn7no5jE+uJR6P07e6GlcqSDSnOo1+LqwnHoy+xVGE6jZZAdr8Z6FpA+zNaPfEyDXc77dkwwTvion433tA53daPkb+yKJhisqWiBHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756216925; c=relaxed/simple; bh=JL2zx+LdVArgj2aBcKbpxBauXC/vkkPUtagm9b6dnbg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=N1ZOD65NZ9R5R5yXFmvafL0WblQgxkYqIVKih6TO1vg4ZO4ckEezFJxZslSLyalYvn1WaU+H9j5pT9lqF/kkwXU+/LYekvu+UYCEmh45Ra0EekZpnF1FcWh/UMYYdHTtpttbQa8WOifUah63O9doEr56Bde9VlgQPTMM1RFLEhQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=n9wk9Tay; 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="n9wk9Tay" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EA8AC4CEF1; Tue, 26 Aug 2025 14:02:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756216924; bh=JL2zx+LdVArgj2aBcKbpxBauXC/vkkPUtagm9b6dnbg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=n9wk9TaycE/fcAzecaWGsZ9kwMJmAE8YVEIXoqHKqu8FsjP1q/TtL2ujTd3ZrE72t E7Q5LAXsgD2RVB2rKdvHA3IflIJoWRtj16Sooikjv4VH+XwUNSZCChayGcNyUwGLwH kr88vGfRwzLLc9Gen+Ws6lnlc2lhe2Ps7E6ud5T4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Jani Nikula , Jani Nikula , Imre Deak , Sasha Levin Subject: [PATCH 5.15 594/644] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS Date: Tue, 26 Aug 2025 13:11:25 +0200 Message-ID: <20250826111001.258970214@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110946.507083938@linuxfoundation.org> References: <20250826110946.507083938@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Imre Deak [ Upstream commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f ] 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 [ call to drm_dp_dpcd_access() instead of drm_dp_dpcd_probe() ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_dp_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -336,7 +336,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_a * monitor doesn't power down exactly after the throw away read. */ if (!aux->is_remote) { - ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_LANE0_1_STATUS, buffer, 1); if (ret != 1) goto out;