[PATCH v11 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism

Shanker Donthineni
2021-07-15T21:32:34Z

Add reset_method sysfs attribute to enable user to query and set user
preferred device reset methods and their ordering.

Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
---
Documentation/ABI/testing/sysfs-bus-pci | 19 +++++
drivers/pci/pci-sysfs.c | 103 ++++++++++++++++++++++++
2 files changed, 122 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 793cbb76cd250..beb94b9c18c78 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -121,6 +121,25 @@ Description:
child buses, and re-discover devices removed earlier
from this part of the device tree.

+What: /sys/bus/pci/devices/.../reset_method
+Date: March 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 will be present in sysfs. Initially reading
+ this file will give names of the device supported reset
+ methods and their ordering. After write, this file will
+ give names and ordering of currently enabled reset methods.
+ Writing the name or comma separated list of names of any of
+ the device supported reset methods to this file will set
+ the reset methods and their ordering to be used when
+ resetting the device. Writing empty string to this file
+ will disable ability to reset the device and writing
+ "default" will return to the original value.
+
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 a1d9b0e83615a..65791d8b07aa5 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1334,6 +1334,108 @@ static const struct attribute_group pci_dev_rom_attr_group = {
.is_bin_visible = pci_dev_rom_attr_is_visible,
};

+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, idx;
+
+ for (i = 0; i < PCI_NUM_RESET_METHODS; i++) {
+ idx = pdev->reset_methods[i];
+ if (!idx)
+ break;
+
+ len += sysfs_emit_at(buf, len, "%s%s", len ? "," : "",
+ pci_reset_fn_methods[idx].name);
+ }
+
+ if (len)
+ len += sysfs_emit_at(buf, len, "\n");
+
+ return len;
+}
+
+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);
+ int n = 0;
+ char *name, *options = NULL;
+ u8 reset_methods[PCI_NUM_RESET_METHODS] = { 0 };
+
+ if (count >= (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ if (sysfs_streq(buf, "")) {
+ pci_warn(pdev, "All device reset methods disabled by user");
+ goto set_reset_methods;
+ }
+
+ if (sysfs_streq(buf, "default")) {
+ pci_init_reset_methods(pdev);
+ return count;
+ }
+
+ options = kstrndup(buf, count, GFP_KERNEL);
+ if (!options)
+ return -ENOMEM;
+
+ while ((name = strsep(&options, ",")) != NULL) {
+ int i;
+
+ if (sysfs_streq(name, ""))
+ continue;
+
+ name = strim(name);
+
+ for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
+ if (sysfs_streq(name, pci_reset_fn_methods[i].name) &&
+ !pci_reset_fn_methods[i].reset_fn(pdev, 1)) {
+ reset_methods[n++] = i;
+ break;
+ }
+ }
+
+ if (i == PCI_NUM_RESET_METHODS) {
+ kfree(options);
+ return -EINVAL;
+ }
+ }
+
+ if (!pci_reset_fn_methods[1].reset_fn(pdev, 1) && reset_methods[0] != 1)
+ pci_warn(pdev, "Device specific reset disabled/de-prioritized by user");
+
+set_reset_methods:
+ memcpy(pdev->reset_methods, reset_methods, sizeof(reset_methods));
+ kfree(options);
+ return count;
+}
+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;
+}
+
+static 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,
+};
+
static ssize_t reset_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
@@ -1491,6 +1593,7 @@ 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,
--
2.25.1