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 BFACE1E500C; Tue, 26 Aug 2025 14:43:21 +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=1756219401; cv=none; b=YBuzECwMmREBl+ZePK9Do6SGbWfUyt2+DRP+7E8OooSFVZHSWCiv+pWCvBLF8XuaHii8LDPIXHFE6g7KQtSA43nTKIVxOR9YeBWNwziiyexrS4JSeZ8POiF87+5wsD2dcuVuj8lqfeK8lEEW9DwmtJnfEO2kZuxrlStNIWtRO6g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756219401; c=relaxed/simple; bh=bM7xvsWM+kpriBdUkr2q4K6QLpy+5z/aTy8yaG5bYV8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=X/UBecKmQdWFpI5khzvbprEFZ34nbnCfO0DBSyvs8qcUz3fSMgoERxOD5J0myYaHS65OKT8z81rZ21gKhETUqECk3lzj5UMkhvRyOTYl3a6CdVe4N32OrxhWY2HYfDAnZkqY9TBZRQff4NataeyQGOEYbls93KOj2Xu5D5R+Tm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=O4Zk+e32; 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="O4Zk+e32" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F094FC4CEF1; Tue, 26 Aug 2025 14:43:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756219401; bh=bM7xvsWM+kpriBdUkr2q4K6QLpy+5z/aTy8yaG5bYV8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O4Zk+e3225W5FH4MI7pL8bNzBCSNRTyGpPF2w46wy+x/oKbREx+o58SluBDAxzQwJ JWUBexSd6e+2TnJgXvDcVxw5mxEsob20jD5SwgqEdhywhdHu9W0CGKluLBQbswj0GI 2YSTqM6ROzPQcb6kwuYM5HgQlpluXDNTh/DYslYg= 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 5.4 368/403] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS Date: Tue, 26 Aug 2025 13:11:34 +0200 Message-ID: <20250826110917.171626200@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110905.607690791@linuxfoundation.org> References: <20250826110905.607690791@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 5.4-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 @@ -280,7 +280,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_a * We just have to do it before any DPCD access and hope that the * monitor doesn't power down exactly after the throw away read. */ - ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_LANE0_1_STATUS, buffer, 1); if (ret != 1) goto out;