[+cc Alex, reset expert] On Mon, Mar 01, 2021 at 06:12:21PM +0100, Pali Rohár wrote: > Hello! > > PCIe card can be reset via in-band Hot Reset signal which can be > triggered by PCIe bridge via Secondary Bus Reset bit in PCI config > space. > > Kernel already exports sysfs node "reset" for triggering Functional > Reset of particular function of PCI device. But in some cases Functional > Reset is not enough and Hot Reset is required. > > Following RFC patch exports sysfs node "reset_bus" for PCI bridges which > triggers Secondary Bus Reset and therefore for PCIe bridges it resets > connected PCIe card. > > What do you think about it? > > Currently there is userspace script which can trigger PCIe Hot Reset by > modifying PCI config space from userspace: > > https://alexforencich.com/wiki/en/pcie/hot-reset-linux > > But because kernel already provides way how to trigger Functional Reset > it could provide also way how to trigger PCIe Hot Reset. > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index 50fcb62d59b5..f5e11c589498 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1321,6 +1321,30 @@ static ssize_t reset_store(struct device *dev, struct device_attribute *attr, > > static DEVICE_ATTR(reset, 0200, NULL, reset_store); > > +static ssize_t reset_bus_store(struct device *dev, struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct pci_dev *pdev = to_pci_dev(dev); > + unsigned long val; > + ssize_t result = kstrtoul(buf, 0, &val); > + > + if (result < 0) > + return result; > + > + if (val != 1) > + return -EINVAL; > + > + pm_runtime_get_sync(dev); > + result = pci_bridge_secondary_bus_reset(pdev); > + pm_runtime_put(dev); > + if (result < 0) > + return result; > + > + return count; > +} > + > +static DEVICE_ATTR(reset_bus, 0200, NULL, reset_bus_store); > + > static int pci_create_capabilities_sysfs(struct pci_dev *dev) > { > int retval; > @@ -1332,8 +1356,15 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev) > if (retval) > goto error; > } > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) { > + retval = device_create_file(&dev->dev, &dev_attr_reset_bus); > + if (retval) > + goto error_reset_bus; > + } > return 0; > > +error_reset_bus: > + device_remove_file(&dev->dev, &dev_attr_reset); > error: > pcie_vpd_remove_sysfs_dev_files(dev); > return retval; > @@ -1414,6 +1445,8 @@ static void pci_remove_capabilities_sysfs(struct pci_dev *dev) > device_remove_file(&dev->dev, &dev_attr_reset); > dev->reset_fn = 0; > } > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) > + device_remove_file(&dev->dev, &dev_attr_reset_bus); > } > > /**
