From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CB12DEF8FE5 for ; Wed, 4 Mar 2026 13:52:13 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6278F10EA27; Wed, 4 Mar 2026 13:52:13 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="SQocogmq"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2234310EA27; Wed, 4 Mar 2026 13:52:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1772632332; x=1804168332; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=YFL3qE0wQPE5w3jx8D26+umnGo/HtN8DLl39vbJd1Dg=; b=SQocogmq8XWdE5YSy3fNfS5wF3ebmqqnpHsdvzRWAGGkiDw7soe2u5xb x4oqAuuHCeKcIDBK72Hpwd6MIMOOlCeKqcVz1p4jZnojxZAN6/dcq/rGM 4ccb9jOieVQouWfKZSOYfZpQxMWcc2O0RI0b/zGxUjV/Fe8x7TF9IERSR xIyV3hMdKO7CaqNLxy8L621fB37Sx053OKlQtqabssK+pgL63Sb9UuqNy K34RO4/+aqUkL35TV6F7oIjc+IwPK+SYx9pvz9Px6aj6Yp5Vv+7e+1Hwr NX9IFjcAw4HN3LWXevs/eBDkptkq8d4mNCZ39nT4dSevSOHw3kCorsdyC Q==; X-CSE-ConnectionGUID: HmhkhHB2REGsjD/vfhrpEQ== X-CSE-MsgGUID: FyglYwehTnqvBYDHyEasSA== X-IronPort-AV: E=McAfee;i="6800,10657,11719"; a="61265258" X-IronPort-AV: E=Sophos;i="6.21,324,1763452800"; d="scan'208";a="61265258" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2026 05:52:12 -0800 X-CSE-ConnectionGUID: UcAByEEdRICJwEx3wRRWSw== X-CSE-MsgGUID: R97t88v8TOu3B1AZVZSqgg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,324,1763452800"; d="scan'208";a="256228923" Received: from smoticic-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.245.149]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2026 05:52:09 -0800 Date: Wed, 4 Mar 2026 15:52:07 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: "Nautiyal, Ankit K" Cc: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, stable@vger.kernel.org, Benjamin Tissoires Subject: Re: [PATCH] drm/i915/vrr: Configure VRR timings after enabling TRANS_DDI_FUNC_CTL Message-ID: References: <20260303095414.4331-1-ville.syrjala@linux.intel.com> <53aa591f-7245-4b4b-b13a-dfa050134000@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53aa591f-7245-4b4b-b13a-dfa050134000@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: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, Mar 04, 2026 at 11:36:12AM +0530, Nautiyal, Ankit K wrote: > > On 3/3/2026 3:24 PM, Ville Syrjala wrote: > > From: Ville Syrjälä > > > > Apparently ICL may hang with an MCE if we write TRANS_VRR_VMAX/FLIPLINE > > before enabling TRANS_DDI_FUNC_CTL. > > > > Personally I was only able to reproduce a hang (on an Dell XPS 7390 > > 2-in-1) with an external display connected via a dock using a dodgy > > type-C cable that made the link training fail. After the failed > > link training the machine would hang. TGL seemed immune to the > > problem for whatever reason. > > > > BSpec does tell us to configure VRR after enabling TRANS_DDI_FUNC_CTL > > as well. The DMC firmware also does the VRR restore in two stages: > > - first stage seems to be unconditional and includes TRANS_VRR_CTL > > and a few other VRR registers, among other things > > - second stage is conditional on the DDI being enabled, > > and includes TRANS_DDI_FUNC_CTL and TRANS_VRR_VMAX/VMIN/FLIPLINE, > > among other things > > > > So let's reorder the steps to match to avoid the hang, and > > toss in an extra WARN to make sure we don't screw this up later. > > > > BSpec: 22243 > > Cc: stable@vger.kernel.org > > Cc: Ankit Nautiyal > > Reported-by: Benjamin Tissoires > > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15777 > > Tested-by: Benjamin Tissoires > > Fixes: dda7dcd9da73 ("drm/i915/vrr: Use fixed timings for platforms that support VRR") > > Signed-off-by: Ville Syrjälä > > You are right. VRR timing registers are indeed supposed to be programmed > after TRANS_DDI_FUNC_CTL. > > Thanks for catching this, Ville, and thanks Benjamin for the bisection. > > Change looks good to me. > > Reviewed-by: Ankit Nautiyal Pushed. Thanks for the review, and the bug report. > > > > --- > > drivers/gpu/drm/i915/display/intel_display.c | 1 - > > drivers/gpu/drm/i915/display/intel_vrr.c | 14 ++++++++++++++ > > 2 files changed, 14 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > > index 27354585ba92..138ee7dd1977 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display.c > > +++ b/drivers/gpu/drm/i915/display/intel_display.c > > @@ -1637,7 +1637,6 @@ static void hsw_configure_cpu_transcoder(const struct intel_crtc_state *crtc_sta > > } > > > > intel_set_transcoder_timings(crtc_state); > > - intel_vrr_set_transcoder_timings(crtc_state); > > > > if (cpu_transcoder != TRANSCODER_EDP) > > intel_de_write(display, TRANS_MULT(display, cpu_transcoder), > > diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c > > index 00ca76dbdd6c..8a957804cb97 100644 > > --- a/drivers/gpu/drm/i915/display/intel_vrr.c > > +++ b/drivers/gpu/drm/i915/display/intel_vrr.c > > @@ -599,6 +599,18 @@ void intel_vrr_set_transcoder_timings(const struct intel_crtc_state *crtc_state) > > if (!HAS_VRR(display)) > > return; > > > > + /* > > + * Bspec says: > > + * "(note: VRR needs to be programmed after > > + * TRANS_DDI_FUNC_CTL and before TRANS_CONF)." > > + * > > + * In practice it turns out that ICL can hang if > > + * TRANS_VRR_VMAX/FLIPLINE are written before > > + * enabling TRANS_DDI_FUNC_CTL. > > + */ > > + drm_WARN_ON(display->drm, > > + !(intel_de_read(display, TRANS_DDI_FUNC_CTL(display, cpu_transcoder)) & TRANS_DDI_FUNC_ENABLE)); > > + > > /* > > * This bit seems to have two meanings depending on the platform: > > * TGL: generate VRR "safe window" for DSB vblank waits > > @@ -961,6 +973,8 @@ void intel_vrr_transcoder_enable(const struct intel_crtc_state *crtc_state) > > { > > struct intel_display *display = to_intel_display(crtc_state); > > > > + intel_vrr_set_transcoder_timings(crtc_state); > > + > > if (!intel_vrr_possible(crtc_state)) > > return; > > -- Ville Syrjälä Intel