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PCI/CXL: Add 'cxl_bus' reset method for devices below CXL Ports

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By default Secondary Bus Reset (SBR) is masked for CXL Ports (see CXL r3.1,
sec 8.1.5.2).

Add cxl_reset_bus_function() (method "cxl_bus") to set the "Unmask SBR" bit
in the upstream CXL Port before performing the bus reset and restore the
original value afterwards.

This method allows the user to perform a bus reset on a CXL device without
needing to set the "Unmask SBR" bit via a user tool.

Link: https://lore.kernel.org/r/20240502165851.1948523-5-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
[bhelgaas: simplify commit log, invert condition to avoid negation]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dave Jiang 2024-05-02 09:57:33 -07:00 committed by Bjorn Helgaas
parent b1956e2d07
commit 53c49b6e6d
2 changed files with 40 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
drivers/pci/pci.c
View File

@ -4980,6 +4980,44 @@ static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
return pci_parent_bus_reset(dev, probe);
}
static int cxl_reset_bus_function(struct pci_dev *dev, bool probe)
{
struct pci_dev *bridge;
u16 dvsec, reg, val;
int rc;
bridge = pci_upstream_bridge(dev);
if (!bridge)
return -ENOTTY;
dvsec = cxl_port_dvsec(bridge);
if (!dvsec)
return -ENOTTY;
if (probe)
return 0;
rc = pci_read_config_word(bridge, dvsec + PCI_DVSEC_CXL_PORT_CTL, &reg);
if (rc)
return -ENOTTY;
if (reg & PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR) {
val = reg;
} else {
val = reg | PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR;
pci_write_config_word(bridge, dvsec + PCI_DVSEC_CXL_PORT_CTL,
val);
}
rc = pci_reset_bus_function(dev, probe);
if (reg != val)
pci_write_config_word(bridge, dvsec + PCI_DVSEC_CXL_PORT_CTL,
reg);
return rc;
}
void pci_dev_lock(struct pci_dev *dev)
{
/* block PM suspend, driver probe, etc. */
@ -5064,6 +5102,7 @@ static const struct pci_reset_fn_method pci_reset_fn_methods[] = {
{ pci_af_flr, .name = "af_flr" },
{ pci_pm_reset, .name = "pm" },
{ pci_reset_bus_function, .name = "bus" },
{ cxl_reset_bus_function, .name = "cxl_bus" },
};
static ssize_t reset_method_show(struct device *dev,

2
include/linux/pci.h
View File

@ -51,7 +51,7 @@
PCI_STATUS_PARITY)
/* Number of reset methods used in pci_reset_fn_methods array in pci.c */
#define PCI_NUM_RESET_METHODS 7
#define PCI_NUM_RESET_METHODS 8
#define PCI_RESET_PROBE true
#define PCI_RESET_DO_RESET false