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 350D5D25B40 for ; Wed, 28 Jan 2026 11:09:01 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E51EA10E6A5; Wed, 28 Jan 2026 11:09:00 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="Nwl9+wO5"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9F91B10E670; Wed, 28 Jan 2026 11:08:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1769598538; x=1801134538; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=O94qbvvf2ZiN2hTRJdwF6VJOBsrqvvkBYizKzu16mgM=; b=Nwl9+wO5OX1ArmGRTy3sBjdiX0Alik9BEEFRmPXw3ZfsvZksbt6LIZLV D9YX46VONcgUtlLORnlXCLuhL2RbHtN7Fcg2Iu1HmVsGuMWc94TuaJXMQ lckqxJ8USPDgez5y//5O5sz745Xyqrk1yqNlsKferBYcHJ7o1C/79hgcJ PPLpSAxnu5mkv08FtJykFRu3zllIqsi8thGsKyhCwbYynqiAox9XQ0tLB p8LuiHq9iBhSx63A/4mFhPpMaDiVsRudZH9Xre8KttIVUkETkDhLY/PPq jkAJZ5XymEH+9lZ/vHn+mDbNaJiSWst2PEDgZd5i1cCMC8uYc9Jg1En8p Q==; X-CSE-ConnectionGUID: w4Vk8xYUSBW3NEn7kBPPJg== X-CSE-MsgGUID: 0DZAhHtvTImNLlB6EigxjA== X-IronPort-AV: E=McAfee;i="6800,10657,11684"; a="70898225" X-IronPort-AV: E=Sophos;i="6.21,258,1763452800"; d="scan'208";a="70898225" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2026 03:08:58 -0800 X-CSE-ConnectionGUID: XEr8HY/RTmKFofnB1GWFSw== X-CSE-MsgGUID: gKI1PtRJTjezk7WFKkzj/A== X-ExtLoop1: 1 Received: from ettammin-mobl2.ger.corp.intel.com (HELO localhost) ([10.245.246.207]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2026 03:08:56 -0800 From: Jani Nikula To: Suraj Kandpal , intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Cc: ankit.k.nautiyal@intel.com, arun.r.murthy@intel.com, Suraj Kandpal Subject: Re: [PATCH] drm/i915/dp: Add a meaningful return to intel_dp_read_dsc_dpcd In-Reply-To: <20260128044904.1293185-1-suraj.kandpal@intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: <20260128044904.1293185-1-suraj.kandpal@intel.com> Date: Wed, 28 Jan 2026 13:08:53 +0200 Message-ID: <51a869ec09c61bd8ba56db858c983bb9667ac11b@intel.com> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Wed, 28 Jan 2026, Suraj Kandpal wrote: > Add a meaningful return to intel_dp_read_dsc_dpcd so tha we avoid > unwanted DPCD reads which are not needed once we know DSC DPCD > read fails. While we are at it remove the drm_err since we do not > shout error during intel_dp_detect phase since it may take time > to come up after pps_on is called for eDP scenario. Please pay more attention to the commit message. > Signed-off-by: Suraj Kandpal > --- > drivers/gpu/drm/i915/display/intel_dp.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 79fd3b8d8b25..d2ed8ec145a2 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -4281,20 +4281,21 @@ static bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp) > return dprx & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED; > } > > -static void intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux, > - u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) > +static int intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux, > + u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) > { > if (drm_dp_dpcd_read(aux, DP_DSC_SUPPORT, dsc_dpcd, > DP_DSC_RECEIVER_CAP_SIZE) < 0) { > - drm_err(aux->drm_dev, > - "Failed to read DPCD register 0x%x\n", > - DP_DSC_SUPPORT); > - return; > + drm_dbg_kms(aux->drm_dev, > + "Could not read DSC DPCD register 0x%x\n", > + DP_DSC_SUPPORT); > + return -EINVAL; If we want to do this properly, then let's propagate the actual error code instead of inventing -EINVAL here. And switch to drm_dp_dpcd_read_data(), which returns an error if not all bytes were transferred (also a case the current implementation completely ignores). Finlly, the debug logging could log the error code. A combo of %pe in the format string and ERR_PTR(ret) in the corresponding parameter will do it nicely. > } > > drm_dbg_kms(aux->drm_dev, "DSC DPCD: %*ph\n", > DP_DSC_RECEIVER_CAP_SIZE, > dsc_dpcd); > + return 0; > } > > static void init_dsc_overall_throughput_limits(struct intel_connector *connector, bool is_branch) > @@ -4345,8 +4346,11 @@ void intel_dp_get_dsc_sink_cap(u8 dpcd_rev, > if (dpcd_rev < DP_DPCD_REV_14) > return; > > - intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > - connector->dp.dsc_dpcd); > + if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > + connector->dp.dsc_dpcd) < 0) { > + drm_err(display->drm, "Failed to read DSC DPCD register\n"); > + return; > + } > > if (drm_dp_dpcd_readb(connector->dp.dsc_decompression_aux, DP_FEC_CAPABILITY, > &connector->dp.fec_capability) < 0) { > @@ -4376,7 +4380,9 @@ static void intel_edp_get_dsc_sink_cap(u8 edp_dpcd_rev, struct intel_connector * > if (edp_dpcd_rev < DP_EDP_14) > return; > > - intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, connector->dp.dsc_dpcd); > + if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > + connector->dp.dsc_dpcd) < 0) > + return; > > if (connector->dp.dsc_dpcd[0] & DP_DSC_DECOMPRESSION_IS_SUPPORTED) > init_dsc_overall_throughput_limits(connector, false); -- Jani Nikula, Intel