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 6C07B72610; Thu, 3 Jul 2025 14:48:48 +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=1751554128; cv=none; b=AuPtxV050ajdpK4UJn7ZYj6f1FXogjoZPaZbsQ5u1RETTedzNkybBIl/YKihE7GbUO9rJhTQi9ORfK2tSfWGsomsp9Lej0p6DitskcPvodX2i89djKQLTUQKDh/ak03l4xOayooN8Cd+dEznpXD0F5jhYf6wCAqySPdOPb3Wv18= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751554128; c=relaxed/simple; bh=z06qb7GynI2NJ2phsTAimxPvHZYhZRVGDFzfi3vtvOM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=eoFRoo3cYPKUs5RQdOA+f19CmTMJKLw5y59DYwByEDilo6a5N+uakyPoM6ZtsrTTBEjpGQo2VSw7RMxIGp8zHavDjtKd8VFhe5ljwes1vPn99mo2rx4gs14u8bQBpbsLyi1XCgO8bhUdMGj43w+Hb4KPql9gpXpRRHxZwMr0/L8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gTM6ZlAj; 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="gTM6ZlAj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D038DC4CEE3; Thu, 3 Jul 2025 14:48:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751554128; bh=z06qb7GynI2NJ2phsTAimxPvHZYhZRVGDFzfi3vtvOM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gTM6ZlAjmtx6ZuR1FpHj33rkf16MH1waj/sB08jGmGFJc9gByhDFXig/W1RD7K7jX fWV4Q0j0KtCax90gUnhcZe42lqZ4HMsNMv1RoB3skQaNJmdcCZBQbdt1SD0t/VafAi 97xpYCzjKNzuwDrFSv0aZ8rzxPm23nQapWf31QHc= 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 , Joonas Lahtinen Subject: [PATCH 6.12 088/218] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS Date: Thu, 3 Jul 2025 16:40:36 +0200 Message-ID: <20250703143959.464767193@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250703143955.956569535@linuxfoundation.org> References: <20250703143955.956569535@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Imre Deak commit a3ef3c2da675a8a564c8bea1a511cdd0a2a9aa49 upstream. 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 (cherry picked from commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f) Signed-off-by: Joonas Lahtinen Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/display/drm_dp_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -664,7 +664,7 @@ 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_probe(aux, DP_DPCD_REV); + ret = drm_dp_dpcd_probe(aux, DP_LANE0_1_STATUS); if (ret < 0) return ret; }