Re: [PATCH v6 5/8] PCI: Store # of supported End-End TLP Prefixes
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Date: 2024-12-11 16:36:34
Also in:
linux-pci, lkml
On Fri, 13 Sep 2024 17:36:29 +0300 Ilpo Järvinen [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 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 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. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> --- drivers/pci/ats.c | 2 +- drivers/pci/probe.c | 14 +++++++++----- include/linux/pci.h | 2 +- include/uapi/linux/pci_regs.h | 1 + 4 files changed, 12 insertions(+), 7 deletions(-)diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c index c570892b2090..e13433dcfc82 100644 --- a/drivers/pci/ats.c +++ b/drivers/pci/ats.c@@ -377,7 +377,7 @@ int pci_enable_pasid(struct pci_dev *pdev, int features) if (WARN_ON(pdev->pasid_enabled)) return -EBUSY; - if (!pdev->eetlp_prefix_path && !pdev->pasid_no_tlp) + if (!pdev->eetlp_prefix_max && !pdev->pasid_no_tlp) return -EINVAL; if (!pasid)diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index b14b9876c030..0ab70ea6840c 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c@@ -2228,8 +2228,8 @@ static void pci_configure_relaxed_ordering(struct pci_dev *dev) static void pci_configure_eetlp_prefix(struct pci_dev *dev) { -#ifdef CONFIG_PCI_PASID struct pci_dev *bridge; + unsigned int eetlp_max; int pcie_type; u32 cap;@@ -2241,15 +2241,19 @@ static void pci_configure_eetlp_prefix(struct pci_dev *dev) return; pcie_type = pci_pcie_type(dev); + + eetlp_max = FIELD_GET(PCI_EXP_DEVCAP2_EE_PREFIX_MAX, cap); + /* 00b means 4 */ + eetlp_max = eetlp_max ?: 4; + if (pcie_type == PCI_EXP_TYPE_ROOT_PORT || pcie_type == PCI_EXP_TYPE_RC_END) - dev->eetlp_prefix_path = 1; + dev->eetlp_prefix_max = eetlp_max; else { bridge = pci_upstream_bridge(dev); - if (bridge && bridge->eetlp_prefix_path) - dev->eetlp_prefix_path = 1; + if (bridge && bridge->eetlp_prefix_max)
What happens if they disagree? That is the bridge supports 2 and the device 3?
+ dev->eetlp_prefix_max = eetlp_max; } -#endif }