From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB01B606A327 for ; Fri, 30 Oct 2026 11:44:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=CYls7XT4 Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id EDD7810E279; Fri, 30 Oct 2026 11:44:31 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5E02E10E279; Fri, 30 Oct 2026 11:44:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1793360665; x=1824896665; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=x8TvwLzSHqdTbx1HgAAtb/ADR1txxIEQrI2u8aFySlM=; b=CYls7XT4FtBzGSHj2wU9DbW89wIHZfPeVF5FqMgn8NqfUGEwU4Zd6hjC rIXf0ZfZg+ynXS1skX35Ithc2FfytK0utj0Xkp2n9wv/KNImj3GE9XNSE mxjSX8+FiAOZMUOOkXLKPHVOCxANiP1jGXJKNzmwKBiUilM3baluiKTN0 9eXghTiBcmOjSZ/cwFv9XIIS8ylE9ygsFMlY5YBWfb+AXmSlL1N+/tMoF q0qKGTq0aeqNlmfAtQlYeLIoqcWiy3vDAH42vxvB8kWTPLVZ5TeSuGaRp mM80lQIXcIVLmOvg9dfUMOGN9ETy7py4tJQ6+NjkZeRTdFJzuCPETkB3t A==; X-CSE-ConnectionGUID: wPJlFmIyQmCr1QolONuI2w== X-CSE-MsgGUID: XqwjpKHXT/ivi0Z6SZhWnQ== X-IronPort-AV: E=McAfee;i="6800,10657,11950"; a="2153576" X-IronPort-AV: E=Sophos;i="6.27,186,1787036400"; d="scan'208";a="2153576" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Oct 2026 04:44:25 -0700 X-CSE-ConnectionGUID: dUGh3GZZSfWnVLY/c5JscA== X-CSE-MsgGUID: GtI3xy5jTpm+UPu/72vcvg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,186,1787036400"; d="scan'208";a="5755803" Received: from abityuts-desk1.ger.corp.intel.com (HELO localhost) ([10.245.244.58]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Oct 2026 04:44:20 -0700 Date: Fri, 30 Oct 2026 13:44:16 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Cc: Dmytro Malovanyi , dri-devel@lists.freedesktop.org, Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Harry Wentland , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Patrik Jakobsson , Lyude Paul , Danilo Krummrich , nouveau@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/5] drm/dp: Always use enhanced framing for DPCD r1.2+ Message-ID: References: <20261029101826.72773-1-dmitrymalovanyy@gmail.com> <20261029101826.72773-2-dmitrymalovanyy@gmail.com> <59106a36510e33e851f76c877f41952b11a8c774@intel.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <59106a36510e33e851f76c877f41952b11a8c774@intel.com> X-Patchwork-Hint: comment Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "dri-devel" X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Fri, Oct 30, 2026 at 01:36:31PM +0200, Jani Nikula wrote: > On Fri, 30 Oct 2026, Ville Syrjälä wrote: > > On Thu, Oct 29, 2026 at 11:18:22AM +0100, Dmytro Malovanyi wrote: > >> DP 1.2 section 2.2.1.1 says "An upstream device interoperating with a > >> downstream device with DPCD Revision of 1.2 or higher must enable > >> Enhanced Framing Mode". So for r1.2+ the DPCD revision is enough, the > >> DP_ENHANCED_FRAME_CAP bit does not need to be checked. > >> > >> Some sinks get this bit wrong. The Xiaomi Monitor A24i (P24FBA-RAGL) > >> sets it in the base receiver caps, but clears it in the extended > >> receiver caps at 0x2200, which are the ones we use: > >> > >> base: 12 0a c4 01 01 00 01 80 02 00 06 00 00 00 81 > >> extended: 14 0a 44 00 01 00 01 80 02 02 06 00 00 00 81 > >> > >> Through a USB4 dock (CalDigit Element 5) the link trains without > >> enhanced framing (0x202-0x204: 77 77 81), but the sink never syncs to > >> the stream (SINK_STATUS 0x205: 00) and shows "No signal". Forcing RBR > >> does not change it. Connected directly to the laptop the same sink > >> syncs without enhanced framing, at RBR, HBR and HBR2. > >> > >> Make drm_dp_enhanced_frame_cap() return true for DPCD r1.2+. This > >> changes behaviour for every driver using the helper, but only for sinks > >> which already violate the spec by not setting the bit. > >> > >> Tested on i915 (Arrow Lake-U), with the dock the link now uses enhanced > >> framing (0x101: 84) and the sink syncs (0x205: 03). > >> > >> Fixes: a1d926527b79 ("drm/i915: implement EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT") > >> Cc: stable@vger.kernel.org > >> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/17719 > >> Suggested-by: Jani Nikula > >> Signed-off-by: Dmytro Malovanyi > >> --- > >> include/drm/display/drm_dp_helper.h | 4 ++++ > >> 1 file changed, 4 insertions(+) > >> > >> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h > >> index 5b05a7fbe..4f20f60db 100644 > >> --- a/include/drm/display/drm_dp_helper.h > >> +++ b/include/drm/display/drm_dp_helper.h > >> @@ -160,6 +160,10 @@ drm_dp_max_lane_count(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) > >> static inline bool > >> drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) > >> { > >> + /* DP 1.2 2.2.1.1: enhanced framing is mandatory for DPCD r1.2+ */ > > > > DP_ENHANCED_FRAME_CAP is also mandatory so I think this needs > > a bit more detailed explanation. > > Commit message not enough? On its face the check looks completely redundant, so without further justification someone is likely to just remove it. > > I think the wording in the specs suggest that with DPCD r1.2+ you should > just enable enhanced framing regardless of the cap. > > BR, > Jani. > > > > >> + if (dpcd[DP_DPCD_REV] >= 0x12) > >> + return true; > >> + > >> return dpcd[DP_DPCD_REV] >= 0x11 && > >> (dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP); > >> } > >> -- > >> 2.50.1 (Apple Git-155) > > -- > Jani Nikula, Intel -- Ville Syrjälä Intel