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, which is missing but there is a reset-gpios property, 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]. All newly registered "reset-gpio" platform devices will be stored on their own list to avoid any duplicated devices. The key to find each of such platform device is the entire Devicetree GPIO specifier: phandle to GPIO controller, GPIO number and GPIO flags. If two devices have conflicting "reset-gpios" property, e.g. with different ACTIVE_xxx flags, this would spawn two separate "reset-gpio" devices, where the second would fail probing on busy GPIO reques Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@xxxxxxxxxxxxxxxxxx/ [1] Cc: Bartosz Golaszewski <brgl@xxxxxxxx> Cc: Sean Anderson <sean.anderson@xxxxxxxx> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> --- drivers/reset/core.c | 176 ++++++++++++++++++++++++++++--- include/linux/reset-controller.h | 4 + 2 files changed, 167 insertions(+), 13 deletions(-) diff --git a/drivers/reset/core.c b/drivers/reset/core.c index 4d5a78d3c085..ec9b3ff419cf 100644 --- a/drivers/reset/core.c +++ b/drivers/reset/core.c @@ -13,6 +13,7 @@ #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 +24,10 @@ static LIST_HEAD(reset_controller_list); static DEFINE_MUTEX(reset_lookup_mutex); static LIST_HEAD(reset_lookup_list); +/* Protects reset_gpio_device_list */ +static DEFINE_MUTEX(reset_gpio_device_mutex); +static LIST_HEAD(reset_gpio_device_list); + /** * struct reset_control - a reset control * @rcdev: a pointer to the reset controller device @@ -63,6 +68,16 @@ struct reset_control_array { struct reset_control *rstc[] __counted_by(num_rstcs); }; +/** + * struct reset_gpio_device - ad-hoc created reset-gpio device + * @of_args: phandle to the reset controller with all the args like GPIO number + * @list: list entry for the reset_lookup_list + */ +struct reset_gpio_device { + 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 +828,119 @@ 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]) + break; + + /* All args matched? */ + if (i == a1->args_count) + return true; + + return false; +} + +/* + * @node: node of the device requesting reset + * @reset_args: phandle to the reset controller with all the args like GPIO number + */ +static int __reset_add_reset_gpio_device(struct device_node *node, + struct of_phandle_args *args) +{ + struct reset_gpio_device *rgpio_dev; + struct platform_device *pdev; + int ret; + + lockdep_assert_not_held(&reset_list_mutex); + + mutex_lock(&reset_gpio_device_mutex); + + list_for_each_entry(rgpio_dev, &reset_gpio_device_list, list) { + if (args->np == rgpio_dev->of_args.np) { + if (__reset_gpios_args_match(args, + &rgpio_dev->of_args)) { + ret = 0; + goto out_unlock; + } + } + } + + /* Not freed in normal path, persisent subsyst data */ + rgpio_dev = kzalloc(sizeof(*rgpio_dev), GFP_KERNEL); + if (!rgpio_dev) { + ret = -ENOMEM; + goto out_unlock; + } + + rgpio_dev->of_args = *args; + pdev = platform_device_register_data(NULL, "reset-gpio", + PLATFORM_DEVID_AUTO, &node, + sizeof(node)); + ret = PTR_ERR_OR_ZERO(pdev); + if (!ret) + list_add(&rgpio_dev->list, &reset_gpio_device_list); + else + kfree(rgpio_dev); + +out_unlock: + mutex_unlock(&reset_gpio_device_mutex); + + return ret; +} + +static struct reset_controller_dev *__reset_find_rcdev(struct of_phandle_args *args, + bool gpio_fallback, + const void *cookie) +{ + 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)) { + /* + * Fake args (take first reset) and + * args_count (to matcg reset-gpio + * of_reset_n_cells) because reset-gpio + * has only one reset and does not care + * about reset of GPIO specifier. + */ + args->args[0] = 0; + args->args_count = 1; + 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; @@ -839,21 +960,50 @@ __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; } + mutex_lock(&reset_list_mutex); + rcdev = __reset_find_rcdev(&args, gpio_fallback, NULL); + if (!rcdev) { - rstc = ERR_PTR(-EPROBE_DEFER); - goto out; + if (gpio_fallback) { + /* + * Registering reset-gpio device might cause immediate + * bind, thus taking reset_list_mutex lock via + * reset_controller_register(). + */ + mutex_unlock(&reset_list_mutex); + ret = __reset_add_reset_gpio_device(node, &args); + mutex_lock(&reset_list_mutex); + if (ret) { + rstc = ERR_PTR(ret); + goto out; + } + /* + * Success: reset-gpio could probe immediately, so + * re-check the lookup. + */ + rcdev = __reset_find_rcdev(&args, gpio_fallback, NULL); + if (!rcdev) { + rstc = ERR_PTR(-EPROBE_DEFER); + goto out; + } + /* Success, rcdev is valid thus do not bail out */ + } else { + rstc = ERR_PTR(-EPROBE_DEFER); + goto out; + } } if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) { 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
