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Wysocki" Subject: Re: [PATCH v7 2/8] PCI: Add new array for keeping track of ordering of reset methods Message-ID: <20210621171518.vs4h4y6ag2benlwp@archlinux> References: <20210608054857.18963-3-ameynarkhede03@gmail.com> <20210617231305.GA3139128@bjorn-Precision-5520> <20210618172242.vs3qwimjpcicb4m4@archlinux> <1fb0a184-908c-5f98-ef6d-74edc602c2e0@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1fb0a184-908c-5f98-ef6d-74edc602c2e0@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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