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 632B621D3C0; Tue, 26 Aug 2025 11:46:23 +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=1756208783; cv=none; b=bEu2QQaaBlMiPDi0cKrWwRAqyhoaBBXtYp7cl1fTW+WiqFaNjYJc0x6UfKvVHrAJJsr5Yt0IUBC1xEBc1n9KtU84386xhvx/zpp9DlXlKSchHWMCoQYTClRnYnDUcP66HFLmY16jzPzGx6BLtDwx9jZR4igWjE90E0qXB0SfSPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756208783; c=relaxed/simple; bh=lhbd1XwlSZLwLQoIq/nVlNaVnAMb3+ZSUA+HgDso7H0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=g3a/+xs6I32DC6ZgMH0n7vpJYPvONJXbVOhlM9Xw4A0PsXU09mtKFMQgocDg/9ZdPxF+iKEqF72KFoXFA7eAzI6lm0r/klTPz+quaHp4eeHIfrOD0hoyaCtjYj7hMUL13fYbXhkqjM4C8WGA5V8FIkH68cpAnOigeHsa/q8yKAE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dqT7BEq+; 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="dqT7BEq+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E4DA4C113CF; Tue, 26 Aug 2025 11:46:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756208783; bh=lhbd1XwlSZLwLQoIq/nVlNaVnAMb3+ZSUA+HgDso7H0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dqT7BEq+0LCz1DtQHNpzBBR3O9ASwtsG/ckl+4QKemEQ+aTxFqMoAb6CqUT8B2fvU 3MLzWBiatjDtdwGclA4DtFTW9zFBcnDYiwLROAhvmRTwQl/6Al79HixAZdSnduWq2s F4WG81EHM/2898H7+IEF5DuTr6pfYPDFHdkqTixU= 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 6.12 212/322] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS Date: Tue, 26 Aug 2025 13:10:27 +0200 Message-ID: <20250826110921.107078254@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110915.169062587@linuxfoundation.org> References: <20250826110915.169062587@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 [ 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 Signed-off-by: Sasha Levin 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; }