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b=UHlCTWgS+EhT6GPUGtyGJBjxfzaNQfindQhVeeMJ0+8A9BytfGMZslLHbFr0wOJS3eRS//K2CDKyIWYZ0LlJmNk9l/CTVwPcrjH3eTJuqNnFN12tYpd5wPFYAg7dxIl1NvH3wPSPMu2WNpZw5TDi0dYg3Bpb088Nde+ByPAiQXM= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DM6PR12MB4877.namprd12.prod.outlook.com (2603:10b6:5:1bb::24) by MN0PR12MB6368.namprd12.prod.outlook.com (2603:10b6:208:3d2::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7828.23; Fri, 2 Aug 2024 04:58:51 +0000 Received: from DM6PR12MB4877.namprd12.prod.outlook.com ([fe80::92ad:22ff:bff2:d475]) by DM6PR12MB4877.namprd12.prod.outlook.com ([fe80::92ad:22ff:bff2:d475%4]) with mapi id 15.20.7828.023; Fri, 2 Aug 2024 04:58:50 +0000 Message-ID: <2fc282b0-97e4-448c-a77e-0ed63746d0a1@amd.com> Date: Thu, 1 Aug 2024 23:58:46 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3 06/10] PCI/TPH: Introduce API to retrieve TPH steering tags from ACPI To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, netdev@vger.kernel.org, Jonathan.Cameron@huawei.com, corbet@lwn.net, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, alex.williamson@redhat.com, gospo@broadcom.com, michael.chan@broadcom.com, ajit.khaparde@broadcom.com, somnath.kotur@broadcom.com, andrew.gospodarek@broadcom.com, manoj.panicker2@amd.com, Eric.VanTassell@amd.com, vadim.fedorenko@linux.dev, horms@kernel.org, bagasdotme@gmail.com, bhelgaas@google.com References: <20240723222229.GA759742@bhelgaas> From: Wei Huang Content-Language: en-US In-Reply-To: <20240723222229.GA759742@bhelgaas> Content-Type: text/plain; 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According to https://members.pcisig.com/wg/PCI-SIG/document/15470, the revision has "4.6.15. _DSM to Query Cache Locality TPH Features". PCI-SIG approved this ECN, but haven't merged it into PCI Firmware Specification 3.3 yet. >> + >> +/** >> + * pcie_tph_get_st_from_acpi() - Retrieve steering tag for a specific CPU >> + * using platform ACPI _DSM > > 1) TPH and Steering Tags are not ACPI-specific, even though the only > current mechanism to learn the tags happens to be an ACPI _DSM, so I > think we should omit "acpi" from the name drivers use. > > 2) The spec doesn't restrict Steering Tags to be for a CPU; it says > "processing resource such as a host processor or system cache > hierarchy ..." But obviously this interface only comprehends an ACPI > CPU ID. Maybe the function name should include "cpu". How about pcie_tph_get_st_for_cpu() or pcie_tph_retreive_st_for_cpu()? >> diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h >> index 854677651d81..b12a592f3d49 100644 >> --- a/include/linux/pci-tph.h >> +++ b/include/linux/pci-tph.h >> @@ -9,15 +9,27 @@ >> #ifndef LINUX_PCI_TPH_H >> #define LINUX_PCI_TPH_H >> >> +enum tph_mem_type { >> + TPH_MEM_TYPE_VM, /* volatile memory type */ >> + TPH_MEM_TYPE_PM /* persistent memory type */ > > Where does this come from? I don't see "vram" or "volatile" used in > the PCIe spec in this context. Maybe this is from the PCI Firmware > spec? > Yes, this is defined in the ECN mentioned above. Do you have concerns about defining them here? If we want to remove it, then pcie_tph_get_st_from_acpi() function can only support one memory type (e.g. vram). Any advice? >> +static inline int pcie_tph_get_st_from_acpi(struct pci_dev *dev, unsigned int cpu_acpi_uid, >> + enum tph_mem_type tag_type, u8 req_enable, >> + u16 *tag) >> +{ return false; } > > "false" is not "int". > > Apparently you want to return "success" in this case, when > CONFIG_PCIE_TPH is not enabled? I suggested leaving this non-exported > for now, which would mean removing this altogether. But if/when we do > export it, I think maybe it should return error so a caller doesn't > assume it succeeded, since *tag will be garbage. > > Bjorn