[PATCH v6 5/8] PCI: Store # of supported End-End TLP Prefixes

Ilpo Järvinen
2024-09-13T14:37:30Z

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)
+ dev->eetlp_prefix_max = eetlp_max;
}
-#endif
}

static void pci_configure_serr(struct pci_dev *dev)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 4cf89a4b4cbc..29b754d32f79 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -398,7 +398,7 @@ struct pci_dev {
supported from root to here */
#endif
unsigned int pasid_no_tlp:1; /* PASID works without TLP Prefix */
- unsigned int eetlp_prefix_path:1; /* End-to-End TLP Prefix */
+ unsigned int eetlp_prefix_max:3; /* Max # of End-End TLP Prefixes, 0=not supported */

pci_channel_state_t error_state; /* Current connectivity state */
struct device dev; /* Generic device interface */
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 94c00996e633..b297bc30ddcb 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -661,6 +661,7 @@
#define PCI_EXP_DEVCAP2_OBFF_MSG 0x00040000 /* New message signaling */
#define PCI_EXP_DEVCAP2_OBFF_WAKE 0x00080000 /* Re-use WAKE# for OBFF */
#define PCI_EXP_DEVCAP2_EE_PREFIX 0x00200000 /* End-End TLP Prefix */
+#define PCI_EXP_DEVCAP2_EE_PREFIX_MAX 0x00c00000 /* Max End-End TLP Prefixes */
#define PCI_EXP_DEVCTL2 0x28 /* Device Control 2 */
#define PCI_EXP_DEVCTL2_COMP_TIMEOUT 0x000f /* Completion Timeout Value */
#define PCI_EXP_DEVCTL2_COMP_TMOUT_DIS 0x0010 /* Completion Timeout Disable */
--
2.39.2