diff options
| author | Dave Jiang <dave.jiang@intel.com> | 2024-05-02 09:57:32 -0700 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2024-05-08 13:25:36 -0500 |
| commit | b1956e2d0713e210a56ae65ad3488ae36f833e76 (patch) | |
| tree | 7a1fe4631df85458c10d92d26d16555c84079fca | |
| parent | 7e89efc6e9e402839643cb297bab14055c547f07 (diff) | |
PCI/CXL: Fail bus reset if upstream CXL Port has SBR masked
Per CXL spec r3.1, sec 8.1.5.2, the Secondary Bus Reset (SBR) bit in the
Bridge Control register of a CXL port has no effect unless the "Unmask SBR"
bit is set.
Return -ENOTTY if we attempt a bus reset on a device below a CXL Port where
"Unmask SBR" is 0. Otherwise, the bus reset would appear to have succeeded
even though setting the bridge SBR bit had no effect.
Link: https://lore.kernel.org/linux-cxl/20240220203956.GA1502351@bhelgaas/
Link: https://lore.kernel.org/r/20240502165851.1948523-4-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
[bhelgaas: simplify commit log and comments]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
| -rw-r--r-- | drivers/pci/pci.c | 42 | ||||
| -rw-r--r-- | include/uapi/linux/pci_regs.h | 5 |
2 files changed, 47 insertions, 0 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c63142352844..225cec964f25 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4928,10 +4928,52 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, bool probe) return pci_reset_hotplug_slot(dev->slot->hotplug, probe); } +static u16 cxl_port_dvsec(struct pci_dev *dev) +{ + return pci_find_dvsec_capability(dev, PCI_VENDOR_ID_CXL, + PCI_DVSEC_CXL_PORT); +} + +static bool cxl_sbr_masked(struct pci_dev *dev) +{ + u16 dvsec, reg; + int rc; + + dvsec = cxl_port_dvsec(dev); + if (!dvsec) + return false; + + rc = pci_read_config_word(dev, dvsec + PCI_DVSEC_CXL_PORT_CTL, ®); + if (rc || PCI_POSSIBLE_ERROR(reg)) + return false; + + /* + * Per CXL spec r3.1, sec 8.1.5.2, when "Unmask SBR" is 0, the SBR + * bit in Bridge Control has no effect. When 1, the Port generates + * hot reset when the SBR bit is set to 1. + */ + if (reg & PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR) + return false; + + return true; +} + static int pci_reset_bus_function(struct pci_dev *dev, bool probe) { + struct pci_dev *bridge = pci_upstream_bridge(dev); int rc; + /* + * If "dev" is below a CXL port that has SBR control masked, SBR + * won't do anything, so return error. + */ + if (bridge && cxl_sbr_masked(bridge)) { + if (probe) + return 0; + + return -ENOTTY; + } + rc = pci_dev_reset_slot_function(dev, probe); if (rc != -ENOTTY) return rc; diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h index a39193213ff2..6024eb2e9a2f 100644 --- a/include/uapi/linux/pci_regs.h +++ b/include/uapi/linux/pci_regs.h @@ -1148,4 +1148,9 @@ #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00ff0000 #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xff000000 +/* Compute Express Link (CXL r3.1, sec 8.1.5) */ +#define PCI_DVSEC_CXL_PORT 3 +#define PCI_DVSEC_CXL_PORT_CTL 0x0c +#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR 0x00000001 + #endif /* LINUX_PCI_REGS_H */ |