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Thu, 15 Jan 2026 15:24:05 +0000 Received: from AS8PR04MB8948.eurprd04.prod.outlook.com ([fe80::843f:752e:60d:3e5e]) by AS8PR04MB8948.eurprd04.prod.outlook.com ([fe80::843f:752e:60d:3e5e%4]) with mapi id 15.20.9499.002; Thu, 15 Jan 2026 15:24:05 +0000 Date: Thu, 15 Jan 2026 10:23:48 -0500 From: Frank Li To: Koichiro Den Cc: jingoohan1@gmail.com, mani@kernel.org, lpieralisi@kernel.org, kwilczynski@kernel.org, robh@kernel.org, bhelgaas@google.com, cassel@kernel.org, vigneshr@ti.com, s-vadapalli@ti.com, hongxing.zhu@nxp.com, l.stach@pengutronix.de, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, minghuan.Lian@nxp.com, mingkai.hu@nxp.com, roy.zang@nxp.com, jesper.nilsson@axis.com, heiko@sntech.de, srikanth.thokala@intel.com, marek.vasut+renesas@gmail.com, yoshihiro.shimoda.uh@renesas.com, geert+renesas@glider.be, magnus.damm@gmail.com, christian.bruel@foss.st.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, thierry.reding@gmail.com, jonathanh@nvidia.com, hayashi.kunihiko@socionext.com, mhiramat@kernel.org, kishon@kernel.org, jirislaby@kernel.org, rongqianfeng@vivo.com, 18255117159@163.com, shawn.lin@rock-chips.com, nicolas.frattaroli@collabora.com, linux.amoon@gmail.com, vidyas@nvidia.com, linux-omap@vger.kernel.org, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@axis.com, linux-rockchip@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-tegra@vger.kernel.org Subject: Re: [PATCH v8 5/5] Documentation: PCI: endpoint: Clarify pci_epc_set_bar() usage Message-ID: References: <20260115084928.55701-1-den@valinux.co.jp> <20260115084928.55701-6-den@valinux.co.jp> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?peQqdrQshvJ00g7WAL6fV6PkTTZgWJAJWrxoMpjB9Hyt2ezUOIkD4uf6s20l?= =?us-ascii?Q?2Dg+8y/ptpu1riis2V/AqCZwuhtnQcQLoDnpr0QzPGtNcNySWwu1qhnKn2/5?= =?us-ascii?Q?VSk4g1yzYs0kb6rmtDMMAPW20I6kFwKJ/1vMpY0NR5kz1UxZMvnRnxJTweuy?= =?us-ascii?Q?SSxL7yFYevtIKRLvBzDHnFKmWAhX9tPUO8b/ItsSHOuB0iCJechigPXvM+PL?= =?us-ascii?Q?9zO4I7G3GjaMm/juGXIHeYNbZdw+wYvTV+6JMtLEMV707B3fQ0uB9SMuLfTf?= =?us-ascii?Q?IUhU7/zN5FRrXhRb2gyidZc3DUCcBeXbTIoRrX+8HFrkPJ/NpxLfizvbPd/j?= =?us-ascii?Q?y4ZociiDEolrtE2j4Kf/2rO72c8U96Emkp3D+Y48kHUoOnqfJz6grLO5cAOr?= =?us-ascii?Q?87weAN5cT3k042Y3wAIBvBIP5rUOg/p9dnGHDGs39B/65cPJ/4o4c0QvsV0k?= =?us-ascii?Q?z3M0oSbenjM1hBoBrzH0ucNNle42gK+zjKcjLwS3fSMQ7LTIyjJyuDRvsvUr?= =?us-ascii?Q?uUy3vKodcUpQYe8PvMJpwmPMqqJC/DtaLlxCgKj5LbREMRJ/IfBG+ndJOx4c?= =?us-ascii?Q?I6oBWR5GQgBZiCTvNyPJsQA6i+WgaocMzX7bqziXnrVsmpgPAduNQmorfB3r?= =?us-ascii?Q?E9n5nZbcropwUfHawmzH/ZL6UnhGaNrcImespSqZu2ZIZSASfGNu3/RKBW6/?= =?us-ascii?Q?cZAfEaXKjf2fuUJyY0Qpp2NwKShKSRK7qUDUOSilFZRk1spb5s/YGFetpiMd?= =?us-ascii?Q?diWzaCbKCyD/nAnUriyN9Nz24S/Yv7fm0XxDt+oiY5vyDH6TZeXjc0cZ4JfQ?= =?us-ascii?Q?ma/KIxFHoklso6czAnLHkNQKgAmeUuQuEQaFiXr5d3lAcpxSRaZlcKvu6Bkl?= =?us-ascii?Q?CQyX68w/IBlCikFXhQNIqb25Kb/TcKmPvLlnlHYINOaYKbvHBWZYMvOU8K/p?= =?us-ascii?Q?v+u6FA6H2Pil5wsj4dHLA12UngQxn7H7JHJCQ1Kq0LWWOYVuiCGGlG4BZeRZ?= =?us-ascii?Q?8Kglz+tqb/2BZiL59Ov/jvC4rFe+PCzuX/aO/I7hDqnxWSsfCARshZnWnfLy?= =?us-ascii?Q?VjEgo9Px0lLrQ7d2hBYSz1Mb1wApORY8p2suV9JzPXsvUNKtv/AVDOgAbyE6?= =?us-ascii?Q?p8a5VrGck3O6y3xuSigjJ0BNLtCsmLTOG54W173znRIQ5CU7A2r+LY9BC/gm?= =?us-ascii?Q?mqMzjJXSCu+yDkBUtQoNvlyrfeaxTaCtKmMLnEfiVhGheDl6F2mzlB+ACDxj?= =?us-ascii?Q?xs6z8NcmheEYvny+6KyYULL8Wta7WDjGjTv2o3sb0L9ER3bW3GLieBRXiBzU?= =?us-ascii?Q?oN2ObEFQMHPNkF8fpoK+wbIJahuushybfJ3df+X+hf7jS1hQk7AMynglL+97?= =?us-ascii?Q?nhhBWUQWBtXwC9VZYpJYTYV6iA8fopAWbuH4PxaUmkxX0OZWBIcJ8o7NfprD?= =?us-ascii?Q?IBKXLVmoDn3ZTo/ZlmkaMXYd0x3jcigK4CYUUv+eV9nBIzZnYtRu8wodxKX7?= =?us-ascii?Q?dMCfusuN2W8TpGTXnPdjJxackAzZ0ym7NbrN0IygHHPAtoL8d/R+ypEPrczv?= =?us-ascii?Q?19wL6eaRCAl1HBfmcvUms6EPe8thqfPA3dlA1toM6Wj+VJGiPxEVE3bWbfzy?= =?us-ascii?Q?wj9OAnSHZ/+MDItOJVA1NXNZcTU9mFzYQ4LDdR++tiTjfxNa2ao31M8Metob?= =?us-ascii?Q?5NUxh12rRuSavywwtamT83d1POqhfNvCjr4EVlRMiTrhl3h3?= X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: ffd74b9c-e802-427a-b22e-08de544a1e8f X-MS-Exchange-CrossTenant-AuthSource: AS8PR04MB8948.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jan 2026 15:24:05.1535 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: l790yAvTGYjBbFSUiagVmk9SsGvkT7IH2EyPpi2QYd39Q0BAyKc2UAmTxsQDZY+VttrAAcyLNstI8Uq7hvjh0Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU2PR04MB8662 On Thu, Jan 15, 2026 at 05:49:28PM +0900, Koichiro Den wrote: > The current documentation implies that pci_epc_set_bar() is only used > before the host enumerates the endpoint. > > In practice, some Endpoint Controllers support calling pci_epc_set_bar() > multiple times for the same BAR (without clearing it) in order to update > inbound address translations after the host has programmed the BAR base > address, which some Endpoint Functions such as vNTB already rely on. > Add document text for that. > > Also document the expected call flow for BAR subrange mapping > (pci_epf_bar.num_submap / pci_epf_bar.submap), which may require a > second pci_epc_set_bar() call after the host has programmed the BAR base > address. > > Signed-off-by: Koichiro Den > --- Reviewed-by: Frank Li > Documentation/PCI/endpoint/pci-endpoint.rst | 24 +++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/Documentation/PCI/endpoint/pci-endpoint.rst b/Documentation/PCI/endpoint/pci-endpoint.rst > index 0741c8cbd74e..4697377adeae 100644 > --- a/Documentation/PCI/endpoint/pci-endpoint.rst > +++ b/Documentation/PCI/endpoint/pci-endpoint.rst > @@ -95,6 +95,30 @@ by the PCI endpoint function driver. > Register space of the function driver is usually configured > using this API. > > + Some endpoint controllers also support calling pci_epc_set_bar() again > + for the same BAR (without calling pci_epc_clear_bar()) to update inbound > + address translations after the host has programmed the BAR base address. > + Endpoint function drivers can check this capability via the > + dynamic_inbound_mapping EPC feature bit. > + > + When pci_epf_bar.num_submap is non-zero, the endpoint function driver is > + requesting BAR subrange mapping using pci_epf_bar.submap. This requires > + the EPC to advertise support via the subrange_mapping EPC feature bit. > + > + When an EPF driver wants to make use of the inbound subrange mapping > + feature, it requires that the BAR base address has been programmed by > + the host during enumeration. Thus, it needs to call pci_epc_set_bar() > + twice for the same BAR (requires dynamic_inbound_mapping): first with > + num_submap set to zero and configuring the BAR size, then after the PCIe > + link is up and the host enumerates the endpoint and programs the BAR > + base address, again with num_submap set to non-zero value. > + > + Note that when making use of the inbound subrange mapping feature, the > + EPF driver must not call pci_epc_clear_bar() between the two > + pci_epc_set_bar() calls, because clearing the BAR can clear/disable the > + BAR register or BAR decode on the endpoint while the host still expects > + the assigned BAR address to remain valid. > + > * pci_epc_clear_bar() > > The PCI endpoint function driver should use pci_epc_clear_bar() to reset > -- > 2.51.0 >