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Sat, 02 Nov 2024 11:32:38 +0000 Date: Sat, 02 Nov 2024 11:32:37 +0000 Message-ID: <86jzdl27my.wl-maz@kernel.org> From: Marc Zyngier To: Manivannan Sadhasivam Cc: Frank Li , Bjorn Helgaas , Richard Zhu , Lucas Stach , Lorenzo Pieralisi , Krzysztof =?UTF-8?B?V2lsY3p5?= =?UTF-8?B?xYRza2k=?= , Rob Herring , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, alyssa@rosenzweig.io, bpf@vger.kernel.org, broonie@kernel.org, jgg@ziepe.ca, joro@8bytes.org, lgirdwood@gmail.com, p.zabel@pengutronix.de, robin.murphy@arm.com, will@kernel.org Subject: Re: [PATCH v3 1/2] PCI: Add enable_device() and disable_device() callbacks for bridges In-Reply-To: <20241102111012.23zwz4et2qkafyca@thinkpad> References: <20241024-imx95_lut-v3-0-7509c9bbab86@nxp.com> <20241024-imx95_lut-v3-1-7509c9bbab86@nxp.com> <20241102111012.23zwz4et2qkafyca@thinkpad> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.4 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: manivannan.sadhasivam@linaro.org, Frank.Li@nxp.com, bhelgaas@google.com, hongxing.zhu@nxp.com, l.stach@pengutronix.de, lpieralisi@kernel.org, kw@linux.com, robh@kernel.org, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, alyssa@rosenzweig.io, bpf@vger.kernel.org, broonie@kernel.org, jgg@ziepe.ca, joro@8bytes.org, lgirdwood@gmail.com, p.zabel@pengutronix.de, robin.murphy@arm.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241102_043241_380914_957CBA4C X-CRM114-Status: GOOD ( 35.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, 02 Nov 2024 11:10:12 +0000, Manivannan Sadhasivam wrote: > > On Thu, Oct 24, 2024 at 06:34:44PM -0400, Frank Li wrote: > > Some PCIe host bridges require special handling when enabling or disabling > > PCIe Endpoints. For example, the i.MX95 platform has a lookup table to map > > Requester IDs to StreamIDs, which are used by the SMMU and MSI controller > > to identify the source of DMA accesses. > > > > Without this mapping, DMA accesses may target unintended memory, which > > would corrupt memory or read the wrong data. > > > > Add a host bridge .enable_device() hook the imx6 driver can use to > > configure the Requester ID to StreamID mapping. The hardware table isn't > > big enough to map all possible Requester IDs, so this hook may fail if no > > table space is available. In that case, return failure from > > pci_enable_device(). > > > > It might make more sense to make pci_set_master() decline to enable bus > > mastering and return failure, but it currently doesn't have a way to return > > failure. > > > > Signed-off-by: Frank Li > > --- > > Change from v2 to v3 > > - use Bjorn suggest's commit message. > > - call disable_device() when error happen. > > > > Change from v1 to v2 > > - move enable(disable)device ops to pci_host_bridge > > --- > > drivers/pci/pci.c | 23 ++++++++++++++++++++++- > > include/linux/pci.h | 2 ++ > > 2 files changed, 24 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index 7d85c04fbba2a..5e0cb9b6f4d4f 100644 > > --- a/drivers/pci/pci.c > > +++ b/drivers/pci/pci.c > > @@ -2056,6 +2056,7 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars) > > static int do_pci_enable_device(struct pci_dev *dev, int bars) > > { > > int err; > > + struct pci_host_bridge *host_bridge; > > struct pci_dev *bridge; > > u16 cmd; > > u8 pin; > > @@ -2068,9 +2069,16 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars) > > if (bridge) > > pcie_aspm_powersave_config_link(bridge); > > > > + host_bridge = pci_find_host_bridge(dev->bus); > > + if (host_bridge && host_bridge->enable_device) { > > + err = host_bridge->enable_device(host_bridge, dev); > > + if (err) > > + return err; > > + } > > How about wrapping the enable/disable part in a helper? > > int pci_host_bridge_enable_device(dev); > void pci_host_bridge_disable_device(dev); > > The definition could be placed in drivers/pci/pci.h as an inline > function. What does it bring? I would see the point if there was another user. But this is very much core infrastructure which doesn't lend itself to duplication. Unless you have something in mind? M. -- Without deviation from the norm, progress is not possible.