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Message-ID: <20210621171518.vs4h4y6ag2benlwp@archlinux>
Date: Mon, 21 Jun 2021 22:45:18 +0530
From: Amey Narkhede <ameynarkhede03@...il.com>
To: Shanker R Donthineni <sdonthineni@...dia.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>, alex.williamson@...hat.com,
Raphael Norwitz <raphael.norwitz@...anix.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
kw@...ux.com, Sinan Kaya <okaya@...nel.org>,
Len Brown <lenb@...nel.org>,
"Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v7 2/8] PCI: Add new array for keeping track of ordering
of reset methods
On 21/06/21 10:02AM, Shanker R Donthineni wrote:
> Hi Bjorn,
>
> On 6/18/21 12:22 PM, Amey Narkhede wrote:
> > I wonder if this would be easier if dev->reset_methods[] contained
> > indices into pci_reset_fn_methods[], highest priority first, with the
> > priority being determined when dev->reset_methods[] is updated. For
> > example:
> >
> > const struct pci_reset_fn_method pci_reset_fn_methods[] = {
> > { }, # 0
> > { &pci_dev_specific_reset, .name = "device_specific" }, # 1
> > { &pci_dev_acpi_reset, .name = "acpi" }, # 2
> > { &pcie_reset_flr, .name = "flr" }, # 3
> > { &pci_af_flr, .name = "af_flr" }, # 4
> > { &pci_pm_reset, .name = "pm" }, # 5
> > { &pci_reset_bus_function, .name = "bus" }, # 6
> > };
> >
> > dev->reset_methods[] = [1, 2, 3, 4, 5, 6]
> > means all reset methods are supported, in the default priority
> > order
> >
> > dev->reset_methods[] = [1, 0, 0, 0, 0, 0]
> > means only pci_dev_specific_reset is supported
> >
> > dev->reset_methods[] = [3, 5, 0, 0, 0, 0]
> > means pcie_reset_flr and pci_pm_reset are supported, in that
> > priority order
> What about keeping two bitmap fields 'resets_supported' and 'resets_enabled' in
> pci_dev object and mange it through sysfs and probe helper function. We can avoid
> two loops multiple paces and takes only 2Bytes of memory to keep track resets.
>
> resets_supported ---> initialized during pci_dev setup
> resets_enabled ---> Exposed to userspace through sysfs by default set to resets_supported
>
> include/linux/pci.h:
> ------------------------
> /* Different types of PCI resets possible, lower number is higher priority */
> #define PCI_RESET_METHOD_DEVSPEC 0
> #define PCI_RESET_METHOD_ACPI 1
> #define PCI_RESET_METHOD_FLR 2
> #define PCI_RESET_METHOD_Af_FLR 3
> #define PCI_RESET_METHOD_PM 4
> #define PCI_RESET_METHOD_BUS 5
> #define PCI_RESET_METHOD_MAX 6
>
> struct pci_dev {
> ...
> u8 resets_supported;
> u8 resets_enabled;
> };
>
> static inline bool pci_reset_supported(struct pci_dev *dev)
> {
> return !!(dev->resets_supported);
> }
>
>
> drivers/pci/pci.c:
> --------------------
> const struct pci_reset_fn_method pci_reset_fn_methods[PCI_RESET_METHOD_MAX] = {
> [PCI_RESET_METHOD_DEVSPEC] = { &pci_dev_specific_reset,
> .name = "device_specific" },
> [PCI_RESET_METHOD_ACPI] = { &pci_dev_acpi_reset, .name = "acpi" },
> [PCI_RESET_METHOD_FLR] = { &pcie_reset_flr, .name = "flr" },
> [PCI_RESET_METHOD_Af_FLR] = { &pci_af_flr, .name = "af_flr" },
> [PCI_RESET_METHOD_PM] = { &pci_pm_reset, .name = "pm" },
> [PCI_RESET_METHOD_BUS] = { &pci_reset_bus_function, .name = "bus" }
> };
>
>
> void pci_init_reset_methods(struct pci_dev *dev)
> {
> int i, rc;
>
> BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_RESET_METHOD_MAX);
> might_sleep();
>
> for (i = 0; i < PCI_RESET_METHOD_MAX; i++) {
> rc = pci_reset_fn_methods[i].reset_fn(dev, PCI_RESET_PROBE);
> if (!rc)
> dev->resets_supported |= BIT(i);
> else if (rc != -ENOTTY)
> break;
> }
> dev->resets_enabled = dev->resets_supported;
> }
>
> int __pci_reset_function_locked(struct pci_dev *dev)
> {
> int i, rc = -ENOTTY;
>
> might_sleep();
>
> for (i = 0; i < PCI_RESET_METHOD_MAX; i++) {
> if (dev->resets_enabled & BIT(i)) {
> rc = pci_reset_fn_methods[i].reset_fn(dev, 0);
> if (rc != -ENOTTY)
> return rc;
> }
> }
>
> if (rc == -ENOTTY)
> pci_warn(dev, "No reset happened reason %s\n",
> !!dev->resets_supported ?
> "disabled by user" : "not supported");
>
> return rc;
> }
>
> drivers/pci/pci-sysfs.c
> ----------------------------
> 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);
> u8 resets_enabled = 0;
> ...
> if (sysfs_streq(options, "default")) {
> pdev->resets_enabled = pdev->resets_supported;
> goto set_reset_methods;
> }
>
> while ((name = strsep(&options, ",")) != NULL) {
> if (sysfs_streq(name, ""))
> continue;
> name = strim(name);
>
> for (i = 0; i < PCI_RESET_METHOD_MAX; i++) {
> if ((pdev->resets_supported & BIT(i)) &&
> sysfs_streq(name, pci_reset_fn_methods[i].name)) {
> resets_enabled |= BIT(i);
> break;
> }
> }
> ...
> }
>
> set_reset_methods:
> kfree(options);
> pdev->resets_enabled = resets_enabled;
> return count;
> }
>
> 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;
>
> for (i = 0; i < PCI_RESET_METHOD_MAX; i++) {
> if (pdev->resets_enabled & BIT(i))
> len += sysfs_emit_at(buf, len, "%s%s",
> len ? "," : "",
> pci_reset_fn_methods[i].name);
> }
> len += sysfs_emit_at(buf, len, len ? "\n" : "");
>
> return len;
> }
>
Thank you for the idea.
Actually that would be coming full circle because Alex, Raphael and I
tried similar approach earlier while prototyping for v2 but this implementation
does look better than what I had at that time.
Thanks,
Amey
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