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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C72CC433F5 for ; Thu, 14 Oct 2021 18:19:07 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id D96C061167 for ; Thu, 14 Oct 2021 18:19:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D96C061167 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6220D6EBFE; Thu, 14 Oct 2021 18:19:06 +0000 (UTC) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by gabe.freedesktop.org (Postfix) with ESMTPS id D1DC46EBFE for ; Thu, 14 Oct 2021 18:19:05 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10137"; a="228044013" X-IronPort-AV: E=Sophos;i="5.85,373,1624345200"; d="scan'208";a="228044013" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2021 11:19:05 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,373,1624345200"; d="scan'208";a="442229718" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.171]) by orsmga006.jf.intel.com with SMTP; 14 Oct 2021 11:19:01 -0700 Received: by stinkbox (sSMTP sendmail emulation); Thu, 14 Oct 2021 21:19:00 +0300 From: Ville Syrjala To: intel-gfx@lists.freedesktop.org Date: Thu, 14 Oct 2021 21:18:56 +0300 Message-Id: <20211014181856.17581-2-ville.syrjala@linux.intel.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20211014181856.17581-1-ville.syrjala@linux.intel.com> References: <20211014181856.17581-1-ville.syrjala@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Intel-gfx] [PATCH 2/2] drm/i915: Disable DSB usage for now 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" From: Ville Syrjälä Turns out the DSB has trouble correctly loading the gamma LUT. >From a cursory look maybe like some entries do not load properly, or they get loaded with some gibberish. Unfortunately our current kms_color/etc. tests do not seem to catch this. I had a brief look at the generated DSB batch and it looked correct. Tried a few quick tricks like writing the index register twice/etc. but didn't see any improvement. Also tried switching to the 10bit gamma mode in case there is yet another issue with the multi-segment mode, but even the 10bit mode was showing issues. Switching to mmio fixes all of it. I suppose one theory is that maybe the DSB bangs on the LUT too quickly and it can't keep up and instead some data either gets dropped or corrupted. To confirm that someone should try to slow down the DSB's progress a bit. Another thought was that maybe the LUT has crappy dual porting and you get contention if you try to load it during active scanout. But why then would the mmio path work, unless it's just sufficiently slow? Whatever the case, this is currently busted so let's disable it until we get to the root of the problem. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3916 Signed-off-by: Ville Syrjälä --- drivers/gpu/drm/i915/i915_pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c index 7655c7a4f904..bfc7bdde73a1 100644 --- a/drivers/gpu/drm/i915/i915_pci.c +++ b/drivers/gpu/drm/i915/i915_pci.c @@ -872,7 +872,7 @@ static const struct intel_device_info jsl_info = { TGL_CURSOR_OFFSETS, \ .has_global_mocs = 1, \ .has_pxp = 1, \ - .display.has_dsb = 1 + .display.has_dsb = 0 /* FIXME: LUT load is broken with DSB */ static const struct intel_device_info tgl_info = { GEN12_FEATURES, -- 2.32.0