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Wed, 8 Jan 2025 20:56:21 +0000 Date: Wed, 8 Jan 2025 15:56:13 -0500 From: Yazen Ghannam To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Lukas Wunner , Jonathan Cameron , linux-kernel@vger.kernel.org, Mahesh J Salgaonkar , Oliver O'Halloran , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v8 5/7] PCI: Store # of supported End-End TLP Prefixes Message-ID: <20250108205613.GB1342186@yaz-khff2.amd.com> References: <20241218143747.3159-1-ilpo.jarvinen@linux.intel.com> <20241218143747.3159-6-ilpo.jarvinen@linux.intel.com> Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241218143747.3159-6-ilpo.jarvinen@linux.intel.com> X-ClientProxiedBy: BN7PR02CA0035.namprd02.prod.outlook.com (2603:10b6:408:20::48) To DM4PR12MB6373.namprd12.prod.outlook.com (2603:10b6:8:a4::7) X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR12MB6373:EE_|DM4PR12MB5747:EE_ X-MS-Office365-Filtering-Correlation-Id: 52b292a2-4003-4fe3-2ec4-08dd3026e789 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014|7053199007; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?iso-8859-1?Q?Rzgnotx1bsd08ZJhXFecQllmrgYwuBYnfhnDBn1DxgRcI5Ijuu6CQbDcS/?= =?iso-8859-1?Q?36eplPXAulzpIY+bg1rrh+UzrDXkoLbyJniBxnsjIwSyLZOl/2QGyw4Kqa?= =?iso-8859-1?Q?74eo0EStemef3IhI2nxnLUU1bXERZp0QGNcpnlg3Fxas0TSF2pOLow5cig?= =?iso-8859-1?Q?AqYP9SybWf6ZKNLd718XHZwbb9O1awbb5o09HFRAplOSXB7k4QpcLDLY0t?= =?iso-8859-1?Q?PNlODnJDN6EWnUdYLzkD8xFNGr7vDlob0hghHrpr+5mTZp9CFgJvSiEeYI?= =?iso-8859-1?Q?YMexhOiofwf0N2CFI1EL0BvGyb4fS4AQ840TxKRqz5xccu4oQPARHklNtZ?= =?iso-8859-1?Q?oMQ6yTD5rFrfyylCosV2gWArYW2BDJ12Kbg5yrtEmGcvkmBskPgFqol5N2?= =?iso-8859-1?Q?/JFaBTisynILDR0KgX3HA6/SfewSUA2c15Tw5kzMDPUbaMlhvQ3VYWtxDg?= =?iso-8859-1?Q?VH+HbFEaZuRyeSvAXJZgO5oIIsGwbdLTDOVjB24CSLUOfi6SV96ZnzIO9g?= =?iso-8859-1?Q?SuTzNtxMwK0pbdK44G1PVR74dTL0r5SVU08yliFMgFAmKAsgZuNgaxfHq2?= =?iso-8859-1?Q?LvWnTeMwYaUTxqoE0RN/ienxFhmvcwVlDcvSECwD8b8oFINBSPx7D4DoFW?= =?iso-8859-1?Q?10hRRWw0LJxdMRa1SIBV/+sHQWFwCNcXqIEGL7ZF2ef0wJvgtYH1VcoJw+?= =?iso-8859-1?Q?AVsduhp/oCzg5GADuPcmyDKA+DqlNDDs+RykpsfzrfUXQaZ5h0Pr9Rni2I?= =?iso-8859-1?Q?ng7bh7va5p6fQjqNZ+JwNmM8lzPrtNbsTHeFfTRhl0o65lElIrN4qW7huk?= =?iso-8859-1?Q?quGezftHHI1G0cigfpzNPoxUTeBSUvQ01ZQcMlr0cV4GDvH9Z/cjDOiBCD?= =?iso-8859-1?Q?fsOUbkkW9xEOdPM+EEUnDxcOSbmNQA6eDeFPQgZNR/bbZyRZTUD7nkTwa2?= =?iso-8859-1?Q?3pkYwSz5RAcTaQftkHkBXW8SLeyearP22yRkzJRhtRdY1FfzUE6UHo0v+v?= =?iso-8859-1?Q?esAtClPUIT/VqUQm4RBgOBiCf5MEDmy9P3FVOK+fmJx501t2H7pem61Nc3?= =?iso-8859-1?Q?sh4hJjjmPucmGSpSt3bnzl+P4AIDNLK19J9kV7gLnLwyie2cl0jK/4Jpbg?= =?iso-8859-1?Q?ypeU6UuTjKZctYMEqe8hryHa5z77yUgGKjupzIwLl6wQOSw7hTExTkQoQ9?= =?iso-8859-1?Q?BfhWEyPL09lX0Z5+g1/zArvcYhSVJNC0cWAFSlWTT9zCqL29bl60v+pRO/?= =?iso-8859-1?Q?GkT8WEGFCq9ZWx4Ot2+Nk3HJSGs4JMZlNNT1b6gwJyPhaNRU+nJzz9UQQL?= =?iso-8859-1?Q?OUlWrNsxB+E+BVBrbHWDExV5fyCBlDBn9x8x5NpC0QdLYIyngSJW8o7tUp?= =?iso-8859-1?Q?aRxqycVaNNIH/pWdkkrB4c7N9Go2tMoLDXI1wzF03C5QfJwTSPW27wQAJu?= =?iso-8859-1?Q?0XQuEsfTOPX7QWXlyzdUtypUjAM7d68+v1Cs7OHQ4JxfjgFGqm23pDb/kj?= =?iso-8859-1?Q?PJ2k0aVCURT+UejzxfIxCBdH85MYIQTmLaBrrSFcewa3EH87HHFT7EIcES?= =?iso-8859-1?Q?dFPHdAUIm8AwZWHXrLNqF2yGg45aigN38TH6hDjyT/1grumDZjnUD3m2pl?= =?iso-8859-1?Q?/+zlaKty6e+/gDyqBgPA35Y04sM8OMT5YA?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 52b292a2-4003-4fe3-2ec4-08dd3026e789 X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB6373.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jan 2025 20:56:20.9786 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: yehb9bFL32tlTI3y7xDZikB9dI7M9piO/YRQCSlOV8T+hOl7rnn9FyD8tsH2F6gP5bqLD7d6W/vmiUpXV2d7sw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5747 On Wed, Dec 18, 2024 at 04:37:45PM +0200, Ilpo Järvinen wrote: > eetlp_prefix_path in the struct pci_dev tells if End-End TLP Prefixes > are supported by the path or not, the value is only calculated if > CONFIG_PCI_PASID is set. > > The Max End-End TLP Prefixes field in the Device Capabilities Register > 2 also tells how many (1-4) End-End TLP Prefixes are supported (PCIe > r6.2 sec 7.5.3.15). The number of supported End-End Prefixes is useful > for reading correct number of DWORDs from TLP Prefix Log register in AER > capability (PCIe r6.2 sec 7.8.4.12). > > Replace eetlp_prefix_path with eetlp_prefix_max and determine the > number of supported End-End Prefixes regardless of CONFIG_PCI_PASID so > that an upcoming commit generalizing TLP Prefix Log register reading > does not have to read extra DWORDs for End-End Prefixes that never will > be there. > > The value stored into eetlp_prefix_max is directly derived from > device's Max End-End TLP Prefixes and does not consider limitations > imposed by bridges or the Root Port beyond supported/not supported > flags. This is intentional for two reasons: > > 1) PCIe r6.2 spec sections r6.1 2.2.10.4 & 6.2.4.4 indicate that TLP > is handled malformed only if the number of prefixes exceed the number > of Max End-End TLP Prefixes, which seems to be the case even if the > device could never receive that many prefixes due to smaller maximum > imposed by a bridge or the Root Port. If TLP parsing is later added, > this distinction is significant in interpreting what is logged by the > TLP Prefix Log registers and the value matching to the Malformed TLP > threshold is going to be more useful. > > 2) TLP Prefix handling happens autonomously on a low layer and the > value in eetlp_prefix_max is not programmed anywhere by the kernel > (i.e., there is no limiter OS can control to prevent sending more > than n TLP Prefixes). > > Signed-off-by: Ilpo Järvinen Reviewed-by: Yazen Ghannam Thanks, Yazen