On Fri, Jan 12, 2024 at 5:36 PM Krzysztof Kozlowski krzysztof.kozlowski@linaro.org wrote:

Add a simple driver to control GPIO-based resets using the reset controller API for the cases when the GPIOs are shared and reset should be coordinated. The driver is expected to be used by reset core framework for ad-hoc reset controllers.

Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Chris Packham chris.packham@alliedtelesis.co.nz Cc: Sean Anderson sean.anderson@seco.com Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org

---

MAINTAINERS | 5 ++ drivers/reset/Kconfig | 9 +++ drivers/reset/Makefile | 1 + drivers/reset/reset-gpio.c | 121 +++++++++++++++++++++++++++++++++++++ 4 files changed, 136 insertions(+) create mode 100644 drivers/reset/reset-gpio.c

diff --git a/MAINTAINERS b/MAINTAINERS index 7fe27cd60e1b..a0fbd4814bc7 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8866,6 +8866,11 @@ F: Documentation/i2c/muxes/i2c-mux-gpio.rst F: drivers/i2c/muxes/i2c-mux-gpio.c F: include/linux/platform_data/i2c-mux-gpio.h

+GENERIC GPIO RESET DRIVER +M: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org +S: Maintained +F: drivers/reset/reset-gpio.c

GENERIC HDLC (WAN) DRIVERS M: Krzysztof Halasa khc@pm.waw.pl S: Maintained diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig index ccd59ddd7610..bb1b5a326eb7 100644 --- a/drivers/reset/Kconfig +++ b/drivers/reset/Kconfig @@ -66,6 +66,15 @@ config RESET_BRCMSTB_RESCAL This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on BCM7216.

+config RESET_GPIO

•   tristate "GPIO reset controller"
  

•   help
  

•     This enables a generic reset controller for resets attached via
  

•     GPIOs.  Typically for OF platforms this driver expects "reset-gpios"
  

•     property.
  

•     If compiled as module, it will be called reset-gpio.
  

config RESET_HSDK bool "Synopsys HSDK Reset Driver" depends on HAS_IOMEM diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile index 8270da8a4baa..fd8b49fa46fc 100644 --- a/drivers/reset/Makefile +++ b/drivers/reset/Makefile @@ -11,6 +11,7 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o +obj-$(CONFIG_RESET_GPIO) += reset-gpio.o obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o obj-$(CONFIG_RESET_IMX7) += reset-imx7.o obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o diff --git a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c new file mode 100644 index 000000000000..0fe482740f1b --- /dev/null +++ b/drivers/reset/reset-gpio.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0

+#include <linux/gpio/consumer.h> +#include <linux/mod_devicetable.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/reset-controller.h>

+struct reset_gpio_priv {

•   struct reset_controller_dev rc;
  

•   struct gpio_desc *reset;
  

+};

+static inline struct reset_gpio_priv +*rc_to_reset_gpio(struct reset_controller_dev *rc) +{

•   return container_of(rc, struct reset_gpio_priv, rc);
  

+}

+static int reset_gpio_assert(struct reset_controller_dev *rc, unsigned long id) +{

•   struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
  

•   gpiod_set_value_cansleep(priv->reset, 1);
  

•   return 0;
  

+}

+static int reset_gpio_deassert(struct reset_controller_dev *rc,

•                          unsigned long id)
  

+{

•   struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
  

•   gpiod_set_value_cansleep(priv->reset, 0);
  

•   return 0;
  

+}

+static int reset_gpio_status(struct reset_controller_dev *rc, unsigned long id) +{

•   struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
  

•   return gpiod_get_value_cansleep(priv->reset);
  

+}

+static const struct reset_control_ops reset_gpio_ops = {

•   .assert = reset_gpio_assert,
  

•   .deassert = reset_gpio_deassert,
  

•   .status = reset_gpio_status,
  

+};

+static int reset_gpio_of_xlate(struct reset_controller_dev *rcdev,

•                          const struct of_phandle_args *reset_spec)
  

+{

•   return reset_spec->args[0];
  

+}

+static void reset_gpio_of_node_put(void *data) +{

•   of_node_put(data);
  

+}

+static int reset_gpio_probe(struct platform_device *pdev) +{

•   struct device *dev = &pdev->dev;
  

•   struct of_phandle_args *platdata = dev_get_platdata(dev);
  

•   struct reset_gpio_priv *priv;
  

•   int ret;
  

•   if (!platdata)
  

•           return -EINVAL;
  

•   priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
  

•   if (!priv)
  

•           return -ENOMEM;
  

•   platform_set_drvdata(pdev, &priv->rc);
  

•   /* Relies on GPIO_LOOKUP */
  

That doesn't mean anything. The GPIO abstraction is there to hide *how* the GPIO is assigned to the device. This relies on regular GPIO infrastructure common to all drivers. If at some point this gets an OF compatible or is instantiated from ACPI or otherwise, the same code will still work and not rely on "GPIO_LOOKUP").

•   priv->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
  

•   if (IS_ERR(priv->reset))
  

•           return dev_err_probe(dev, PTR_ERR(priv->reset),
  

•                                "Could not get reset gpios\n");
  

•   priv->rc.ops = &reset_gpio_ops;
  

•   priv->rc.owner = THIS_MODULE;
  

•   priv->rc.dev = dev;
  

•   priv->rc.of_args = platdata;
  

•   priv->rc.of_node = of_node_get(platdata->np);
  

•   ret = devm_add_action_or_reset(dev, reset_gpio_of_node_put,
  

•                                  priv->rc.of_node);
  

•   if (ret)
  

•           return ret;
  

•   /* Cells to match GPIO specifier, but it's not really used */
  

•   priv->rc.of_reset_n_cells = 2;
  

•   priv->rc.of_xlate = reset_gpio_of_xlate;
  

•   priv->rc.nr_resets = 1;
  

•   return devm_reset_controller_register(dev, &priv->rc);
  

+}

+static const struct platform_device_id reset_gpio_ids[] = {

•   { .name = "reset-gpio", },
  

•   {}
  

+}; +MODULE_DEVICE_TABLE(platform, reset_gpio_ids);

+static struct platform_driver reset_gpio_driver = {

•   .probe          = reset_gpio_probe,
  

•   .id_table       = reset_gpio_ids,
  

•   .driver = {
  

•           .name = "reset-gpio",
  

•   },
  

+}; +module_platform_driver(reset_gpio_driver);

+MODULE_AUTHOR("Krzysztof Kozlowski krzysztof.kozlowski@linaro.org"); +MODULE_DESCRIPTION("Generic GPIO reset driver");

+MODULE_LICENSE("GPL");

2.34.1

With the above dropped:

Reviewed-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org

On Fri, Jan 12, 2024 at 5:36 PM Krzysztof Kozlowski krzysztof.kozlowski@linaro.org 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@robh.at.kernel.org/ [1] Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Chris Packham chris.packham@alliedtelesis.co.nz Cc: Sean Anderson sean.anderson@seco.com Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org

---

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

On Fr, 2024-01-12 at 17:36 +0100, Krzysztof Kozlowski wrote: [...]

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

[...]

@@ -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;

+}

How about making this

return a2 && a1->np == a2->np && a1->args_count == a2->args_count && !memcmp(a1->args, a2->args, sizeof(a1->args[0]) * a1->args_count);

?

There's similar code in include/linux/cpufreq.h, maybe this could later be lifted into a common of_phandle_args_equal().

+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;
• 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));
• if (!gdev)

• return -EPROBE_DEFER;
  

• label = kstrdup(gpio_device_get_label(gdev), GFP_KERNEL);
• if (!label)

• return -EINVAL;
  

The kstrdup() failure looks like it should be -ENOMEM to me. I'd check the gpio_device_get_label(gdev) return value separately.

Is this going to be in v6.8-rc1, or does using gpio_device_get_label() introduce a dependency?

• /* 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));
• return 0;

+}

+/*

• • @reset_args: phandle to the GPIO provider with all the args like GPIO number

s/reset_//

• */

+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);
• 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);
• 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;

Now that this is moved into a function, there's no need for the r, rcdev split anymore. Just return a match when found, and NULL at the end:

struct reset_controller_dev *rcdev;

• lockdep_assert_held(&reset_list_mutex);
• rcdev = NULL;
• list_for_each_entry(r, &reset_controller_list, list) {

list_for_each_entry(rcdev, &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;
  

return rcdev;

• 		}
  

• 	} else {
  

• 		rcdev = r;
  

• 		break;
  

• 	}
  

• }
  

With the np check moved into __reset_gpios_args_match() above, the whole loop could be turned into:

if (gpio_fallback) { if (__reset_gpios_args_match(args, rcdev->of_args)) return rcdev; } else { if (args->np == rcdev->of_node) return rcdev; }

Explicitly checking against rcdev->of_args->np instead of rcdev-

of_node in gpio_fallback mode could avoid false positives in case

anybody ever creates a combined GPIO and reset controller device and then uses its GPIOs to drive a shared reset line..

• }
• return rcdev;

return NULL;

+}

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};

Is this still needed?

• 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)) {

Nice. I like that the __of_reset_control_get() changes are much less invasive now.

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);

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

Any plans what to do about this? With the above changes we could mandate that either of_node or of_args should be set, never both.

• • @of_args: for reset-gpios controllers: corresponding phandle args with GPIO

• •       number complementing of_node
    

regards Philipp

On Fr, 2024-01-12 at 17:36 +0100, Krzysztof Kozlowski wrote: [...]

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) {

I think this should continue to return optional ? NULL : ERR_PTR(ret) if !IS_ENABLED(CONFIG_RESET_GPIO), for example by just skipping the of_parse_phandle_with_args(). That should allow the GPIO fallback in patch 5 to work as expected.

• /*
  

•  * 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;
  

  } }

regards Philipp

On Fr, 2024-01-12 at 17:36 +0100, Krzysztof Kozlowski wrote:

From: Chris Packham chris.packham@alliedtelesis.co.nz

Some hardware designs with multiple PCA954x devices use a reset GPIO connected to all the muxes. Support this configuration by making use of the reset controller framework which can deal with the shared reset GPIOs. Fall back to the old GPIO descriptor method if the reset controller framework is not enabled.

Signed-off-by: Chris Packham chris.packham@alliedtelesis.co.nz Acked-by: Peter Rosin peda@axentia.se Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://lore.kernel.org/r/20240108041913.7078-1-chris.packham@alliedtelesis.... Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org

---

If previous patches are fine, then this commit is independent and could be taken via I2C.

Cc: Chris Packham chris.packham@alliedtelesis.co.nz Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Sean Anderson sean.anderson@seco.com

---

drivers/i2c/muxes/i2c-mux-pca954x.c | 46 ++++++++++++++++++++++++----- 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 2219062104fb..1702e8d49b91 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -49,6 +49,7 @@ #include <linux/pm.h> #include <linux/property.h> #include <linux/regulator/consumer.h> +#include <linux/reset.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <dt-bindings/mux/mux.h> @@ -102,6 +103,9 @@ struct pca954x { unsigned int irq_mask; raw_spinlock_t lock; struct regulator *supply;

• struct gpio_desc *reset_gpio;
• struct reset_control *reset_cont;

};

/* Provide specs for the MAX735x, PCA954x and PCA984x types we know about */ @@ -477,6 +481,35 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data) return ret; }

+static int pca954x_get_reset(struct device *dev, struct pca954x *data) +{

• data->reset_cont = devm_reset_control_get_optional_shared(dev, NULL);
• if (IS_ERR(data->reset_cont))

• return dev_err_probe(dev, PTR_ERR(data->reset_cont),
  

• 		     "Failed to get reset\n");
  

• else if (data->reset_cont)

• return 0;
  

• /*

• * fallback to legacy reset-gpios
  

• */
  

devm_reset_control_get_optional_shared() won't return NULL if the "reset-gpios" property is found in the device tree, so the GPIO fallback is dead code.

• data->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
• if (IS_ERR(data->reset_gpio)) {

• return dev_err_probe(dev, PTR_ERR(data->reset_gpio),
  

• 		     "Failed to get reset gpio");
  

• }
• return 0;

+}

regards Philipp

On Di, 2024-01-16 at 19:58 +0000, Chris Packham wrote:

On 17/01/24 04:18, Philipp Zabel wrote:

...

On Fr, 2024-01-12 at 17:36 +0100, Krzysztof Kozlowski wrote:

...

From: Chris Packham chris.packham@alliedtelesis.co.nz

Some hardware designs with multiple PCA954x devices use a reset GPIO connected to all the muxes. Support this configuration by making use of the reset controller framework which can deal with the shared reset GPIOs. Fall back to the old GPIO descriptor method if the reset controller framework is not enabled.

Signed-off-by: Chris Packham chris.packham@alliedtelesis.co.nz Acked-by: Peter Rosin peda@axentia.se Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://scanmail.trustwave.com/?c=20988&d=8p6m5Tfi2yYJWYV9xYGcYnz7UYxB6W... Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org

---

If previous patches are fine, then this commit is independent and could be taken via I2C.

Cc: Chris Packham chris.packham@alliedtelesis.co.nz Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Sean Anderson sean.anderson@seco.com

---

drivers/i2c/muxes/i2c-mux-pca954x.c | 46 ++++++++++++++++++++++++----- 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 2219062104fb..1702e8d49b91 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -49,6 +49,7 @@ #include <linux/pm.h> #include <linux/property.h> #include <linux/regulator/consumer.h> +#include <linux/reset.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <dt-bindings/mux/mux.h> @@ -102,6 +103,9 @@ struct pca954x { unsigned int irq_mask; raw_spinlock_t lock; struct regulator *supply;

• struct gpio_desc *reset_gpio;

• struct reset_control *reset_cont; };

  /* Provide specs for the MAX735x, PCA954x and PCA984x types we know about */

@@ -477,6 +481,35 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data) return ret; }

+static int pca954x_get_reset(struct device *dev, struct pca954x *data) +{

• data->reset_cont = devm_reset_control_get_optional_shared(dev, NULL);
• if (IS_ERR(data->reset_cont))

• return dev_err_probe(dev, PTR_ERR(data->reset_cont),
  

• 		     "Failed to get reset\n");
  

• else if (data->reset_cont)

• return 0;
  

• /*

• * fallback to legacy reset-gpios
  

• */
  

devm_reset_control_get_optional_shared() won't return NULL if the "reset-gpios" property is found in the device tree, so the GPIO fallback is dead code.

Hmm, I was attempting to handle the case where CONFIG_RESET_GPIO wasn't set [...] [...] it looks like we'd get -EPROBE_DEFER. I could change to check for that or just remove the GPIO fallback entirely. Any preference?

I hadn't considered this.

If CONFIG_RESET_GPIO=n, devm_reset_control_get_optional_shared() probably shouldn't return -EPROBE_DEFER. If we change that, the GPIO fallback here can stay as is.

The alternative would be to drop the fallback and select RESET_GPIO. Using -EPROBE_DEFER for fallback detection is no good, as there could be a valid probe deferral if reset-gpio is compiled as a module that will be loaded later.

regards Philipp