On Fri, Jan 12, 2024 at 5:36 PM Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: > > Devices sharing a reset GPIO could use the reset framework for > coordinated handling of that shared GPIO line. We have several cases of > such needs, at least for Devicetree-based platforms. > > If Devicetree-based device requests a reset line, while "resets" > Devicetree property is missing but there is a "reset-gpios" one, > instantiate a new "reset-gpio" platform device which will handle such > reset line. This allows seamless handling of such shared reset-gpios > without need of changing Devicetree binding [1]. > > To avoid creating multiple "reset-gpio" platform devices, store the > Devicetree "reset-gpios" GPIO specifiers used for new devices on a > linked list. Later such Devicetree GPIO specifier (phandle to GPIO > controller, GPIO number and GPIO flags) is used to check if reset > controller for given GPIO was already registered. > > If two devices have conflicting "reset-gpios" property, e.g. with > different ACTIVE_xxx flags, this would allow to spawn two separate > "reset-gpio" devices, where the second would fail probing on busy GPIO > request. > > Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@xxxxxxxxxxxxxxxxxx/ [1] > Cc: Bartosz Golaszewski <brgl@xxxxxxxx> > Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > Cc: Sean Anderson <sean.anderson@xxxxxxxx> > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > --- > drivers/reset/core.c | 227 +++++++++++++++++++++++++++++-- > include/linux/reset-controller.h | 4 + > 2 files changed, 217 insertions(+), 14 deletions(-) > > diff --git a/drivers/reset/core.c b/drivers/reset/core.c > index 4d5a78d3c085..86e33a703ad2 100644 > --- a/drivers/reset/core.c > +++ b/drivers/reset/core.c > @@ -10,9 +10,13 @@ > #include <linux/export.h> > #include <linux/kernel.h> > #include <linux/kref.h> > +#include <linux/gpio/driver.h> > +#include <linux/gpio/machine.h> > +#include <linux/idr.h> > #include <linux/module.h> > #include <linux/of.h> > #include <linux/acpi.h> > +#include <linux/platform_device.h> > #include <linux/reset.h> > #include <linux/reset-controller.h> > #include <linux/slab.h> > @@ -23,6 +27,11 @@ static LIST_HEAD(reset_controller_list); > static DEFINE_MUTEX(reset_lookup_mutex); > static LIST_HEAD(reset_lookup_list); > > +/* Protects reset_gpio_lookup_list */ > +static DEFINE_MUTEX(reset_gpio_lookup_mutex); > +static LIST_HEAD(reset_gpio_lookup_list); > +static DEFINE_IDA(reset_gpio_ida); > + > /** > * struct reset_control - a reset control > * @rcdev: a pointer to the reset controller device > @@ -63,6 +72,16 @@ struct reset_control_array { > struct reset_control *rstc[] __counted_by(num_rstcs); > }; > > +/** > + * struct reset_gpio_lookup - lookup key for ad-hoc created reset-gpio devices > + * @of_args: phandle to the reset controller with all the args like GPIO number > + * @list: list entry for the reset_gpio_lookup_list > + */ > +struct reset_gpio_lookup { > + struct of_phandle_args of_args; > + struct list_head list; > +}; > + > static const char *rcdev_name(struct reset_controller_dev *rcdev) > { > if (rcdev->dev) > @@ -813,13 +832,183 @@ static void __reset_control_put_internal(struct reset_control *rstc) > kref_put(&rstc->refcnt, __reset_control_release); > } > > +static bool __reset_gpios_args_match(const struct of_phandle_args *a1, > + const struct of_phandle_args *a2) > +{ > + unsigned int i; > + > + if (!a2) > + return false; > + > + if (a1->args_count != a2->args_count) > + return false; > + > + for (i = 0; i < a1->args_count; i++) > + if (a1->args[i] != a2->args[i]) > + return false; > + > + return true; > +} > + > +static int __reset_add_reset_gpio_lookup(int id, struct device_node *np, > + unsigned int gpio, > + unsigned int of_flags) > +{ > + struct gpiod_lookup_table *lookup __free(kfree) = NULL; > + struct gpio_device *gdev __free(gpio_device_put) = NULL; > + char *label __free(kfree) = NULL; I got yelled at by Linus Torvalds personally for doing it like this. I know this is a common pattern in code using GLib but Linus wants auto variables to be initialized where they're declared... > + unsigned int lookup_flags; > + > + /* > + * Later we map GPIO flags between OF and Linux, however not all > + * constants from include/dt-bindings/gpio/gpio.h and > + * include/linux/gpio/machine.h match each other. > + */ > + if (of_flags > GPIO_ACTIVE_LOW) { > + pr_err("reset-gpio code does not support GPIO flags %u for GPIO %u\n", > + of_flags, gpio); > + return -EINVAL; > + } > + > + gdev = gpio_device_find_by_fwnode(of_fwnode_handle(np)); ... so this should become: struct gpio_device *gdev __free(gpio_device_put) = gpio_device_find(...) and same for the rest. Don't get me wrong, I love cleanup.h but there's a (unofficial for now) coding style. > + if (!gdev) > + return -EPROBE_DEFER; > + > + label = kstrdup(gpio_device_get_label(gdev), GFP_KERNEL); > + if (!label) > + return -EINVAL; > + > + /* Size: one lookup entry plus sentinel */ > + lookup = kzalloc(struct_size(lookup, table, 2), GFP_KERNEL); > + if (!lookup) > + return -ENOMEM; > + > + lookup->dev_id = kasprintf(GFP_KERNEL, "reset-gpio.%d", id); > + if (!lookup->dev_id) > + return -ENOMEM; > + > + lookup_flags = GPIO_PERSISTENT; > + lookup_flags |= of_flags & GPIO_ACTIVE_LOW; > + lookup->table[0] = GPIO_LOOKUP(no_free_ptr(label), gpio, "reset", > + lookup_flags); > + > + gpiod_add_lookup_table(no_free_ptr(lookup)); You told me that this doesn't need to be removed or ever freed but a comment on that would be in order. > + > + return 0; > +} > + > +/* > + * @reset_args: phandle to the GPIO provider with all the args like GPIO number > + */ > +static int __reset_add_reset_gpio_device(const struct of_phandle_args *args) > +{ > + struct reset_gpio_lookup *rgpio_dev; > + struct platform_device *pdev; > + int id, ret; > + > + /* > + * Registering reset-gpio device might cause immediate > + * bind, resulting in its probe() registering new reset controller thus > + * taking reset_list_mutex lock via reset_controller_register(). > + */ > + lockdep_assert_not_held(&reset_list_mutex); So how does dumping the stack help here exactly? > + > + mutex_lock(&reset_gpio_lookup_mutex); > + > + list_for_each_entry(rgpio_dev, &reset_gpio_lookup_list, list) { > + if (args->np == rgpio_dev->of_args.np) { > + if (__reset_gpios_args_match(args, &rgpio_dev->of_args)) > + goto out; /* Already on the list, done */ > + } > + } > + > + id = ida_alloc(&reset_gpio_ida, GFP_KERNEL); > + if (id < 0) { > + ret = id; > + goto err_unlock; > + } > + > + /* > + * Not freed in normal path, persisent subsystem data (which is assumed > + * also in the reset-gpio driver). > + */ > + rgpio_dev = kzalloc(sizeof(*rgpio_dev), GFP_KERNEL); > + if (!rgpio_dev) { > + ret = -ENOMEM; > + goto err_ida_free; > + } > + > + ret = __reset_add_reset_gpio_lookup(id, args->np, args->args[0], > + args->args[1]); > + if (ret < 0) > + goto err_kfree; > + > + rgpio_dev->of_args = *args; > + /* > + * We keep the device_node reference, but of_args.np is put at the end > + * of __of_reset_control_get(), so get it one more time. > + * Hold reference as long as rgpio_dev memory is valid. > + */ > + of_node_get(rgpio_dev->of_args.np); > + pdev = platform_device_register_data(NULL, "reset-gpio", id, > + &rgpio_dev->of_args, > + sizeof(rgpio_dev->of_args)); > + ret = PTR_ERR_OR_ZERO(pdev); > + if (ret) > + goto err_put; > + > + list_add(&rgpio_dev->list, &reset_gpio_lookup_list); > + > +out: > + mutex_unlock(&reset_gpio_lookup_mutex); > + > + return 0; > + > +err_put: > + of_node_put(rgpio_dev->of_args.np); > +err_kfree: > + kfree(rgpio_dev); > +err_ida_free: > + ida_free(&reset_gpio_ida, id); > +err_unlock: > + mutex_unlock(&reset_gpio_lookup_mutex); > + You're already using cleanup helpers above, why not here too? Would make this function much more readable and allow you to drop all but the ida_free() here. Possibly you'd need to define the __free() callback for of_node_put() though. > + return ret; > +} > + > +static struct reset_controller_dev *__reset_find_rcdev(const struct of_phandle_args *args, > + bool gpio_fallback) > +{ > + struct reset_controller_dev *r, *rcdev; > + > + lockdep_assert_held(&reset_list_mutex); > + > + rcdev = NULL; > + list_for_each_entry(r, &reset_controller_list, list) { > + if (args->np == r->of_node) { > + if (gpio_fallback) { > + if (__reset_gpios_args_match(args, r->of_args)) { > + rcdev = r; > + break; > + } > + } else { > + rcdev = r; > + break; > + } > + } > + } > + > + return rcdev; > +} > + > struct reset_control * > __of_reset_control_get(struct device_node *node, const char *id, int index, > bool shared, bool optional, bool acquired) > { > + struct of_phandle_args args = {0}; > + bool gpio_fallback = false; > struct reset_control *rstc; > - struct reset_controller_dev *r, *rcdev; > - struct of_phandle_args args; > + struct reset_controller_dev *rcdev; > int rstc_id; > int ret; > > @@ -839,39 +1028,49 @@ __of_reset_control_get(struct device_node *node, const char *id, int index, > index, &args); > if (ret == -EINVAL) > return ERR_PTR(ret); > - if (ret) > - return optional ? NULL : ERR_PTR(ret); > + if (ret) { > + /* > + * There can be only one reset-gpio for regular devices, so > + * don't bother with GPIO index. > + */ > + ret = of_parse_phandle_with_args(node, "reset-gpios", "#gpio-cells", > + 0, &args); > + if (ret) > + return optional ? NULL : ERR_PTR(ret); > > - mutex_lock(&reset_list_mutex); > - rcdev = NULL; > - list_for_each_entry(r, &reset_controller_list, list) { > - if (args.np == r->of_node) { > - rcdev = r; > - break; > + gpio_fallback = true; > + > + ret = __reset_add_reset_gpio_device(&args); > + if (ret) { > + rstc = ERR_PTR(ret); > + goto out_put; > } > } > > + mutex_lock(&reset_list_mutex); > + rcdev = __reset_find_rcdev(&args, gpio_fallback); > if (!rcdev) { > rstc = ERR_PTR(-EPROBE_DEFER); > - goto out; > + goto out_unlock; > } > > if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) { > rstc = ERR_PTR(-EINVAL); > - goto out; > + goto out_unlock; > } > > rstc_id = rcdev->of_xlate(rcdev, &args); > if (rstc_id < 0) { > rstc = ERR_PTR(rstc_id); > - goto out; > + goto out_unlock; > } > > /* reset_list_mutex also protects the rcdev's reset_control list */ > rstc = __reset_control_get_internal(rcdev, rstc_id, shared, acquired); > > -out: > +out_unlock: > mutex_unlock(&reset_list_mutex); > +out_put: > of_node_put(args.np); I suggest reworking this to use cleanup.h as well. Bartosz > > return rstc; > diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h > index 0fa4f60e1186..e064473215de 100644 > --- a/include/linux/reset-controller.h > +++ b/include/linux/reset-controller.h > @@ -61,6 +61,9 @@ struct reset_control_lookup { > * @dev: corresponding driver model device struct > * @of_node: corresponding device tree node as phandle target > * @of_reset_n_cells: number of cells in reset line specifiers > + * TODO: of_args have of_node, so we have here duplication > + * @of_args: for reset-gpios controllers: corresponding phandle args with GPIO > + * number complementing of_node > * @of_xlate: translation function to translate from specifier as found in the > * device tree to id as given to the reset control ops, defaults > * to :c:func:`of_reset_simple_xlate`. > @@ -74,6 +77,7 @@ struct reset_controller_dev { > struct device *dev; > struct device_node *of_node; > int of_reset_n_cells; > + const struct of_phandle_args *of_args; > int (*of_xlate)(struct reset_controller_dev *rcdev, > const struct of_phandle_args *reset_spec); > unsigned int nr_resets; > -- > 2.34.1 >
