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Tue, 8 Sep 2026 06:38:58 -0500 From: Chenyu Chen To: CC: Harry Wentland , Leo Li , Aurabindo Pillai , Roman Li , Wayne Lin , Tom Chung , "Fangzhi Zuo" , Dan Wheeler , Ray Wu , Ivan Lipski , Alex Hung , James Lin , Chenyu Chen , Chenyu Chen Subject: [PATCH 36/66] drm/amd/display: Force DSC to 8bpp for SST DP tunneling over USB4 Date: Tue, 8 Sep 2026 19:31:29 +0800 Message-ID: <20260908113338.2433445-37-chen-yu.chen@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260908113338.2433445-1-chen-yu.chen@amd.com> References: <20260908113338.2433445-1-chen-yu.chen@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF0000A890:EE_|CH1PPF5EBD457EF:EE_ X-MS-Office365-Filtering-Correlation-Id: bfcb8bd8-9e3a-4da2-9710-08df0d9dcae4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; ARA:13230040|36860700016|376014|23010399003|1800799024|82310400026|56012099006|11063799006|3023799007|10067099003|22082099003|18002099003; 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DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: sBCIOASCA4cH0JPMAGSG2YSSmnnkGnyEJTMFEovZTQr3F+YelJI8v2jgKLUkEFGwe7ZBli3hW4/0kPd+WEySBHybEcfIWvmDT4SBZbRMRcoEYvQygucikEswzpdCdHTgiO8tScRDKfkrHwcPbgFSeVEnSNhaNfKp85QUMrdMBC4VG7QrVAYM8ULs/l6C5lQX7N6KOL0RWrZSqzLeUBu+CAVUe9YwIeEI+w9gQtC63KW9gCq2W6IWC493hPi/DLDIPsrfpr6EUn7DpZrlnt91P2l88AsWXjmXq9X1S8G8n8GMWt4KSWTKXVOVlQef2rMfNWrN3J3X86imXm2OYWMJzPwQr3j999YaZPx50gMl1q9zV2LU8t2hH3C4Piv4vaLdtLSf3os6XPBNjf4KWHVlqazrBktsHVpdcAopsECrQMy7Hd9XNwKdolsJ+jd/83Am X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2026 11:39:07.4478 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bfcb8bd8-9e3a-4da2-9710-08df0d9dcae4 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF0000A890.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH1PPF5EBD457EF X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" From: Fangzhi Zuo A 4K144 display attached through a USB4 (Thunderbolt) dock does not light up on DCN4.2. The native DP link bandwidth reported for the sink is far larger than the USB4 tunnel can carry, so DSC is sized to the link and the resulting stream overflows the tunnel's granted bandwidth. The bandwidth allocation request fails and the display stays dark. When the endpoint is a USB4 DPIA with BW allocation enabled, force DSC and cap the target to 8 bpp in SST mode. This keeps the compressed stream within the tunnel budget and reserves headroom for other DP tunnels sharing the same host router. Reviewed-by: Roman Li Signed-off-by: Fangzhi Zuo Signed-off-by: Chenyu Chen --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c index c9c8db972922..9dfaaac2828d 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c @@ -1264,6 +1264,12 @@ static void apply_dsc_policy_for_stream(struct amdgpu_dm_connector *aconnector, link_bandwidth_kbps = dc_link_bandwidth_kbps(aconnector->dc_link, dc_link_get_link_cap(aconnector->dc_link)); + if (aconnector->dc_link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA && + aconnector->dc_link->dpia_bw_alloc_config.bw_alloc_enabled) { + dsc_options.max_target_bpp_limit_override_x16 = 8 * 16; + dsc_options.force_dsc_when_not_needed = true; + } + /* Set DSC policy according to dsc_clock_en */ dc_dsc_policy_set_enable_dsc_when_not_needed( aconnector->dsc_settings.dsc_force_enable == DSC_CLK_FORCE_ENABLE); -- 2.43.0