by Amey Narkhede

[permalink] [raw]

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

2021-06-21 18:40:53

by Bjorn Helgaas

[permalink] [raw]

Subject: Re: [PATCH v7 2/8] PCI: Add new array for keeping track of ordering of reset methods

On Mon, Jun 21, 2021 at 10:45:18PM +0530, Amey Narkhede wrote:
> On 21/06/21 10:02AM, Shanker R Donthineni wrote:
> > 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.

I thought part of the point of this series was to allow the user to
change the *order* of reset types. I don't think we can control the
ordering if we only keep a bit (or even two) per reset type.