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Tue, 26 Aug 2025 12:21:14 +0000 Date: Tue, 26 Aug 2025 15:21:08 +0300 From: Imre Deak To: Greg Kroah-Hartman CC: , , Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , Jani Nikula , Jani Nikula , "Sasha Levin" Subject: Re: [PATCH 6.16 293/457] drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS Message-ID: Reply-To: References: <20250826110937.289866482@linuxfoundation.org> <20250826110944.623704248@linuxfoundation.org> Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250826110944.623704248@linuxfoundation.org> X-ClientProxiedBy: DB8P191CA0016.EURP191.PROD.OUTLOOK.COM (2603:10a6:10:130::26) To SJ0PR11MB4845.namprd11.prod.outlook.com (2603:10b6:a03:2d1::10) Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ0PR11MB4845:EE_|MN2PR11MB4632:EE_ X-MS-Office365-Filtering-Correlation-Id: f700b451-1a75-47de-410c-08dde49b0ca0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|10070799003|1800799024|376014|366016|7053199007; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?iso-8859-1?Q?QE3FsQOMtBJxIHZwzQwI/qCwAghAih+RLPBhIThqcXROVjTuJnMix5uFPL?= =?iso-8859-1?Q?J2GmaNM/mSlVE7FdWMVMbVVU4f0ElbaqmxN4IYoyxnxF6qUmY04wIH7/FN?= =?iso-8859-1?Q?GfjEb/rsDqyLLqDm9ryNm2a2ouvrw4fueuQj/Kk9ilylymjQFWpwJkhKTU?= =?iso-8859-1?Q?ZDcWqhuGpwHbYHRW2PyJQ9lxgZzPDVFbf/MKs3u8V+VulUJaGtcHfWkli5?= =?iso-8859-1?Q?xFTwjoaqimoTm1FIpXu07OvPK4zt2aMEcPGSxBNszAisiAmLFDXmqtyfLG?= =?iso-8859-1?Q?O9IFlYblR5UTxIILxrwsc56Aa794/+k3wQdfkzow6TaV22859muYyd3xIm?= =?iso-8859-1?Q?rQxBWh4WWLSC+EliXbc++yCs8X9JBwayWYmMn5KdxakQPit81jQG6xl8XM?= =?iso-8859-1?Q?it8b/t8N4iXOO+6nKhKY6dGvAGzUrU4rryrVHxHPM0qleWPoreqJLTQusB?= =?iso-8859-1?Q?kosFt90UhKDFe2AiHtq3UJm2/FvIG4R08JYtGP1vxI+KIki0xCXQlojFI9?= =?iso-8859-1?Q?6ty8mz38zwrK5yRz20QJ+aYmVfcKzDJQSKfkpvDu5AFdm87wlfxmool1O2?= =?iso-8859-1?Q?ZFcHpP/lWXXxDi5k0GQJTmcldR735ug75bcHPxDj8TqY06DUYmoKtw1F2W?= =?iso-8859-1?Q?F3xQJiWWq9GtLoH44Gp/9T273FOUAsOAa/RvcJk3EDjY6rRLJdQ8kBsh+I?= =?iso-8859-1?Q?TmNdgg/+KsaScQhCtD/vaYOjM6TZ2Qybj3ipcosEqTldpiuik+myVjAYZA?= =?iso-8859-1?Q?KfanPClxpuFist1hbNqZWCbeuktyJYbUl6naLH6FEUgqVt1TkU51a6jGfP?= =?iso-8859-1?Q?e0VyPCPUN3b9uY0pk59YnTj+dgygh/aYsxA5hK7PDs8xyXNgz93Jo9YeJG?= =?iso-8859-1?Q?uxqhFGIVOS0xPTOWltrHz1HUxCmBbZOOGK6BDUFVqFftbVkGB3O0U6WIff?= =?iso-8859-1?Q?+/0K/Ip1gr08ZBBh15aT+iubxQB4BKglzdMGyy5m1axZt2Sf3c1A99HCM8?= =?iso-8859-1?Q?5jbDaG218aUAImrCbDohfK9cV2sVooIwCv1kGTUFJGYU7hisdFP4q/+qm6?= =?iso-8859-1?Q?UZ/Fy5sS8GELiZ1lJLtPuGgaQ6kc5CbzRlhi3g3VAp7pmmG4MGijdGdnT6?= =?iso-8859-1?Q?OovDNfH1JiUQfz9eAE2KaJt9rjmmOS/u7s9URicENg9zcroR76/bCfMmsz?= =?iso-8859-1?Q?ae6rHGwAOWEoyn58DBg9xO4VLeqmSnh2BvGgsg4ab1Okh0eC7mEGWq/aio?= =?iso-8859-1?Q?mNHD95B/BZylaswfxX1GL3QYg3DYj2ehXujskb8P5Cim6A4fseQo9wYmY+?= =?iso-8859-1?Q?Q67o0uYjkSpaR6bWqCuH1odMk/BUF5XmBaiM2LCObi6orfytCZyhp1VjaL?= =?iso-8859-1?Q?HhnVVM995Ql0WbMLX830xojBLDA89iUDdicsLC/Gef+/WpFM+U90HWM84r?= =?iso-8859-1?Q?wC4BYs3nRk2QY906FBqDpkJnWhX9fHijhRTCWuhhlmuCFPUmBvZRCZUNxE?= =?iso-8859-1?Q?0CcdWJ1ekTWdx7wABZBNsuth37UT8rq4eDSHV11ARoqZq1MBN8nEGiKpSv?= =?iso-8859-1?Q?+v7tFIlMisgzwTRDb70SdTMg1l4dvokDMFYRrd01VOxK6R/r9w1OHp3dFd?= =?iso-8859-1?Q?us0tcCXbY4+mNVcifhW/qraYIychhyTER7Fdcsog5erGG0JagGFPLLjIiQ?= =?iso-8859-1?Q?zvv/Wo08BUw2jtQ9mX6v6z8NGY0FprEJlYFePVds?= X-MS-Exchange-CrossTenant-Network-Message-Id: f700b451-1a75-47de-410c-08dde49b0ca0 X-MS-Exchange-CrossTenant-AuthSource: SJ0PR11MB4845.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Aug 2025 12:21:14.0865 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: FR9UgXn7KpbjHS9NUdyI2KbLYWtwTUjNH+AeEMRUP/ogiWet0k0nlgYYhgATEzXmffiHOpybnsKG6+gdd55Dug== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR11MB4632 X-OriginatorOrg: intel.com Hi Greg, could you please drop this patch from all the stable tree queues? I got a review notification now for the 6.12 and 6.16 stable tree, but I also see the patch in all the stable queues (5.4, 5.10, 5.15, 6.1, 6.6, 6.12, 6.16). The change would cause a regression which I described at https://lore.kernel.org/all/aKwQfhfSu5aCUktw@ideak-desk and https://lore.kernel.org/stable/aGaiASySvb3BVXlM@ideak-desk Thanks, Imre On Tue, Aug 26, 2025 at 01:09:37PM +0200, Greg Kroah-Hartman wrote: > 6.16-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Imre Deak > > [ Upstream commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f ] > > Reading DPCD registers has side-effects in general. In particular > accessing registers outside of the link training register range > (0x102-0x106, 0x202-0x207, 0x200c-0x200f, 0x2216) is explicitly > forbidden by the DP v2.1 Standard, see > > 3.6.5.1 DPTX AUX Transaction Handling Mandates > 3.6.7.4 128b/132b DP Link Layer LTTPR Link Training Mandates > > Based on my tests, accessing the DPCD_REV register during the link > training of an UHBR TBT DP tunnel sink leads to link training failures. > > Solve the above by using the DP_LANE0_1_STATUS (0x202) register for the > DPCD register access quirk. > > Cc: > Cc: Ville Syrjälä > Cc: Jani Nikula > Acked-by: Jani Nikula > Signed-off-by: Imre Deak > Link: https://lore.kernel.org/r/20250605082850.65136-2-imre.deak@intel.com > [ DP_TRAINING_PATTERN_SET => DP_LANE0_1_STATUS ] > Signed-off-by: Sasha Levin > Signed-off-by: Greg Kroah-Hartman > --- > drivers/gpu/drm/display/drm_dp_helper.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/drivers/gpu/drm/display/drm_dp_helper.c > +++ b/drivers/gpu/drm/display/drm_dp_helper.c > @@ -725,7 +725,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_a > * monitor doesn't power down exactly after the throw away read. > */ > if (!aux->is_remote) { > - ret = drm_dp_dpcd_probe(aux, DP_TRAINING_PATTERN_SET); > + ret = drm_dp_dpcd_probe(aux, DP_LANE0_1_STATUS); > if (ret < 0) > return ret; > } > >