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Message-ID: <20210809112337.GD867@raphael-debian-dev>
Date: Mon, 9 Aug 2021 11:23:38 +0000
From: Raphael Norwitz <raphael.norwitz@...anix.com>
To: Amey Narkhede <ameynarkhede03@...il.com>
CC: Bjorn Helgaas <bhelgaas@...gle.com>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
Raphael Norwitz <raphael.norwitz@...anix.com>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kw@...ux.com" <kw@...ux.com>,
Shanker Donthineni <sdonthineni@...dia.com>,
Sinan Kaya <okaya@...nel.org>, Len Brown <lenb@...nel.org>,
"Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v15 5/9] PCI: Allow userspace to query and set device
reset mechanism
On Thu, Aug 05, 2021 at 09:59:13PM +0530, Amey Narkhede wrote:
> 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@...hat.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@...anix.com>
> ---
> Documentation/ABI/testing/sysfs-bus-pci | 19 ++++
> drivers/pci/pci-sysfs.c | 1 +
> drivers/pci/pci.c | 117 ++++++++++++++++++++++++
> drivers/pci/pci.h | 2 +
> 4 files changed, 139 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index ef00fada2efb..ef66b62bf025 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@...il.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 space 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@...hat.com>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 316f70c3e3b4..54ee7193b463 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 8a516e9ca316..53d73770881f 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5132,6 +5132,123 @@ 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 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 i, m = 0, n = 0;
> + char *name, *options;
> +
> + if (count >= (PAGE_SIZE - 1))
> + return -EINVAL;
> +
> + if (sysfs_streq(buf, "")) {
> + goto exit;
> + }
> +
> + 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) {
> + if (sysfs_streq(name, ""))
> + continue;
> +
> + name = strim(name);
> +
> + for (m = 1; m < PCI_NUM_RESET_METHODS; m++) {
> + if (sysfs_streq(name, pci_reset_fn_methods[m].name))
> + break;
> + }
> +
> + if (m == PCI_NUM_RESET_METHODS) {
> + pci_warn(pdev, "Skip invalid reset method '%s'", name);
> + continue;
> + }
> +
> + for (i = 0; i < n; i++) {
> + if (pdev->reset_methods[i] == m)
> + break;
> + }
> +
> + if (i < n)
> + continue;
> +
> + if (pci_reset_fn_methods[m].reset_fn(pdev, 1)) {
> + pci_warn(pdev, "Unsupported reset method '%s'", name);
> + continue;
> + }
> +
> + pdev->reset_methods[n++] = m;
> + BUG_ON(n == PCI_NUM_RESET_METHODS);
> + }
> +
> + kfree(options);
> +
> +exit:
> + /* All the reset methods are invalid */
> + if (n == 0 && m == PCI_NUM_RESET_METHODS)
> + return -EINVAL;
> + pdev->reset_methods[n] = 0;
> + if (pdev->reset_methods[0] == 0) {
> + pci_warn(pdev, "All device reset methods disabled by user");
> + } else if ((pdev->reset_methods[0] != 1) &&
> + !pci_reset_fn_methods[1].reset_fn(pdev, 1)) {
> + pci_warn(pdev, "Device specific reset disabled/de-prioritized by user");
> + }
> + 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;
> +}
> +
> +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 7438953745e0..31458d48eda7 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -714,4 +714,6 @@ 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 */
> --
> 2.32.0
>
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