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b=ixj5bkQoIM9qbAJ+EePAm10K5cRhFrhgTG17dCeqBsQTfGyl7QIGBYR2gIi6zXpBGsiTdR0WXsWt6BhMtggKHSGuHY3KUDqIJ9XcnvySvuoCA9BUNKacGPus7IRMJTqPx7DoU+0tfMOl9rUdMhXDzaYDiFhvxXHyxPzLBVTr3sc= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DM4PR12MB8476.namprd12.prod.outlook.com (2603:10b6:8:17e::15) by DS7PR12MB9551.namprd12.prod.outlook.com (2603:10b6:8:24f::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.428.13; Fri, 18 Sep 2026 18:08:57 +0000 Received: from DM4PR12MB8476.namprd12.prod.outlook.com ([fe80::2d79:122f:c62b:1cd8]) by DM4PR12MB8476.namprd12.prod.outlook.com ([fe80::2d79:122f:c62b:1cd8%3]) with mapi id 15.21.0428.008; Fri, 18 Sep 2026 18:08:57 +0000 Message-ID: <18a8b7ee-d588-48be-bfe4-0b79309e3339@amd.com> Date: Fri, 18 Sep 2026 12:08:55 -0600 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/amd/display: Preserve eDP mode on initial ASSR failure To: Arthur Heymans , amd-gfx@lists.freedesktop.org Cc: harry.wentland@amd.com, sunpeng.li@amd.com, siqueira@igalia.com, alexander.deucher@amd.com, christian.koenig@amd.com, michael.mityushkin@amd.com, nicholas.kazlauskas@amd.com, qingqing.zhuo@amd.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, "Zhang, George" References: <20260912151137.3913987-1-arthur@aheymans.xyz> Content-Language: en-US From: Alex Hung In-Reply-To: <20260912151137.3913987-1-arthur@aheymans.xyz> Content-Type: text/plain; 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Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] > > Commit 56d8ce9d8c17 ("drm/amd/display: Apply correct panel mode when > reinitializing hardware") made ASSR failure fall back to the default panel > mode unless eDP mode had previously been applied. > > However, dc_link is zero-initialized and DP_PANEL_MODE_DEFAULT is zero. > Before the first call to dp_set_panel_mode(), panel_mode therefore looks > like a previously applied default mode. If ASSR setup fails during the > first link training attempt, the driver incorrectly trains the eDP link > using the default scrambling mode. > > On a Google Vilboz Chromebook running self-built coreboot firmware and > PSP verstage, this leaves the panel mostly black with corrupted output > along the top edge. > > Track whether panel_mode has actually been initialized, and only consult > the saved mode after it has been applied. This retains the recovery > behavior while preserving eDP mode during initial link training. > > Fixes: 56d8ce9d8c17 ("drm/amd/display: Apply correct panel mode when reinitializing hardware") > Cc: stable@vger.kernel.org # v6.4+ > Assisted-by: Pi:gpt-5.6-sol > Signed-off-by: Arthur Heymans > --- > drivers/gpu/drm/amd/display/dc/dc.h | 1 + > .../amd/display/dc/link/protocols/link_edp_panel_control.c | 4 +++- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h > index 4ecd5699ac5e..0db55a73da0c 100644 > --- a/drivers/gpu/drm/amd/display/dc/dc.h > +++ b/drivers/gpu/drm/amd/display/dc/dc.h > @@ -1912,6 +1912,7 @@ struct dc_scratch_space { > struct ddc_service *ddc; > > enum dp_panel_mode panel_mode; > + bool panel_mode_initialized; > bool aux_mode; > > /* Private to DC core */ > diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c > index 9883216dcc9d..cd90576bc6f0 100644 > --- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c > +++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c > @@ -93,6 +93,7 @@ void dp_set_panel_mode(struct dc_link *link, enum dp_panel_mode panel_mode) > } > > link->panel_mode = panel_mode; > + link->panel_mode_initialized = true; > DC_LOG_DETECTION_DP_CAPS("%d eDP panel mode supported: %d, enabled: %d\n", > link->link_index, > link->dpcd_caps.panel_mode_edp, > @@ -1300,7 +1301,8 @@ void edp_set_panel_assr(struct dc_link *link, struct pipe_ctx *pipe_ctx, > > result = cp_psp->funcs.enable_assr(cp_psp->handle, link); > > - if (!result && link->panel_mode != DP_PANEL_MODE_EDP) > + if (!result && link->panel_mode_initialized && > + link->panel_mode != DP_PANEL_MODE_EDP) > *panel_mode = DP_PANEL_MODE_DEFAULT; > } > } > -- > 2.55.0