From d88f521da3efd698e36d0d504a2abba6ac4f5ef8 Mon Sep 17 00:00:00 2001
From: Amey Narkhede <ameynarkhede03@gmail.com>
Date: Tue, 17 Aug 2021 23:34:56 +0530
Subject: [PATCH] PCI: Allow userspace to query and set device reset mechanism
Git-commit: d88f521da3efd698e36d0d504a2abba6ac4f5ef8
References: jsc#SLE-19359
Patch-mainline: v5.15-rc1
Add "reset_method" sysfs attribute to enable user to query and set
preferred device reset methods and their ordering.
[bhelgaas: on invalid sysfs input, return error and preserve previous
config, as in earlier patch versions]
Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/r/20210817180500.1253-6-ameynarkhede03@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
Documentation/ABI/testing/sysfs-bus-pci | 17 ++++
drivers/pci/pci-sysfs.c | 1 +
drivers/pci/pci.c | 122 ++++++++++++++++++++++++
drivers/pci/pci.h | 2 +
4 files changed, 142 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 793cbb76cd25..d4ae03296861 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -121,6 +121,23 @@ Description:
child buses, and re-discover devices removed earlier
from this part of the device tree.
+What: /sys/bus/pci/devices/.../reset_method
+Date: August 2021
+Contact: Amey Narkhede <ameynarkhede03@gmail.com>
+Description:
+ Some devices allow an individual function to be reset
+ without affecting other functions in the same slot.
+
+ For devices that have this support, a file named
+ reset_method is present in sysfs. Reading this file
+ gives names of the supported and enabled reset methods and
+ their ordering. Writing a space-separated list of names of
+ reset methods sets the reset methods and ordering to be
+ used when resetting the device. Writing an empty string
+ disables the ability to reset the device. Writing
+ "default" enables all supported reset methods in the
+ default ordering.
+
What: /sys/bus/pci/devices/.../reset
Date: July 2009
Contact: Michael S. Tsirkin <mst@redhat.com>
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index a1d9b0e83615..2fd44c97b7ec 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1491,6 +1491,7 @@ const struct attribute_group *pci_dev_groups[] = {
&pci_dev_config_attr_group,
&pci_dev_rom_attr_group,
&pci_dev_reset_attr_group,
+ &pci_dev_reset_method_attr_group,
&pci_dev_vpd_attr_group,
#ifdef CONFIG_DMI
&pci_dev_smbios_attr_group,
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 5ead8826c702..6da5f6d87f6a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5132,6 +5132,128 @@ static const struct pci_reset_fn_method pci_reset_fn_methods[] = {
{ pci_reset_bus_function, .name = "bus" },
};
+static ssize_t reset_method_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ ssize_t len = 0;
+ int i, m;
+
+ for (i = 0; i < PCI_NUM_RESET_METHODS; i++) {
+ m = pdev->reset_methods[i];
+ if (!m)
+ break;
+
+ len += sysfs_emit_at(buf, len, "%s%s", len ? " " : "",
+ pci_reset_fn_methods[m].name);
+ }
+
+ if (len)
+ len += sysfs_emit_at(buf, len, "\n");
+
+ return len;
+}
+
+static int reset_method_lookup(const char *name)
+{
+ int m;
+
+ for (m = 1; m < PCI_NUM_RESET_METHODS; m++) {
+ if (sysfs_streq(name, pci_reset_fn_methods[m].name))
+ return m;
+ }
+
+ return 0; /* not found */
+}
+
+static ssize_t reset_method_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ char *options, *name;
+ int m, n;
+ u8 reset_methods[PCI_NUM_RESET_METHODS] = { 0 };
+
+ if (sysfs_streq(buf, "")) {
+ pdev->reset_methods[0] = 0;
+ pci_warn(pdev, "All device reset methods disabled by user");
+ return count;
+ }
+
+ if (sysfs_streq(buf, "default")) {
+ pci_init_reset_methods(pdev);
+ return count;
+ }
+
+ options = kstrndup(buf, count, GFP_KERNEL);
+ if (!options)
+ return -ENOMEM;
+
+ n = 0;
+ while ((name = strsep(&options, " ")) != NULL) {
+ if (sysfs_streq(name, ""))
+ continue;
+
+ name = strim(name);
+
+ m = reset_method_lookup(name);
+ if (!m) {
+ pci_err(pdev, "Invalid reset method '%s'", name);
+ goto error;
+ }
+
+ if (pci_reset_fn_methods[m].reset_fn(pdev, 1)) {
+ pci_err(pdev, "Unsupported reset method '%s'", name);
+ goto error;
+ }
+
+ if (n == PCI_NUM_RESET_METHODS - 1) {
+ pci_err(pdev, "Too many reset methods\n");
+ goto error;
+ }
+
+ reset_methods[n++] = m;
+ }
+
+ reset_methods[n] = 0;
+
+ /* Warn if dev-specific supported but not highest priority */
+ if (pci_reset_fn_methods[1].reset_fn(pdev, 1) == 0 &&
+ reset_methods[0] != 1)
+ pci_warn(pdev, "Device-specific reset disabled/de-prioritized by user");
+ memcpy(pdev->reset_methods, reset_methods, sizeof(pdev->reset_methods));
+ kfree(options);
+ return count;
+
+error:
+ /* Leave previous methods unchanged */
+ kfree(options);
+ return -EINVAL;
+}
+static DEVICE_ATTR_RW(reset_method);
+
+static struct attribute *pci_dev_reset_method_attrs[] = {
+ &dev_attr_reset_method.attr,
+ NULL,
+};
+
+static umode_t pci_dev_reset_method_attr_is_visible(struct kobject *kobj,
+ struct attribute *a, int n)
+{
+ struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
+
+ if (!pci_reset_supported(pdev))
+ return 0;
+
+ return a->mode;
+}
+
+const struct attribute_group pci_dev_reset_method_attr_group = {
+ .attrs = pci_dev_reset_method_attrs,
+ .is_visible = pci_dev_reset_method_attr_is_visible,
+};
+
/**
* __pci_reset_function_locked - reset a PCI device function while holding
* the @dev mutex lock.
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ebeacb3dbe1e..b31afd4669cc 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -718,4 +718,6 @@ static inline int pci_acpi_program_hp_params(struct pci_dev *dev)
extern const struct attribute_group aspm_ctrl_attr_group;
#endif
+extern const struct attribute_group pci_dev_reset_method_attr_group;
+
#endif /* DRIVERS_PCI_H */
--
2.26.2