From 53c49b6e6dd2ebc1d3257ae838e067699229bc8d Mon Sep 17 00:00:00 2001 From: Dave Jiang Date: Thu, 2 May 2024 09:57:33 -0700 Subject: PCI/CXL: Add 'cxl_bus' reset method for devices below CXL Ports 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 [bhelgaas: simplify commit log, invert condition to avoid negation] Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron Reviewed-by: Dan Williams --- drivers/pci/pci.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'drivers/pci') diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 225cec964f25..13605261a881 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -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, ®); + 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, -- cgit v1.2.3