[PATCH] gpio: pca953x_gpio: support optional reset-gpios property
The DT bindings for the pca953x family has an optional reset-gpios property. If present, ensure that the device is taken out of reset before attempting to read from it.
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk --- drivers/gpio/pca953x_gpio.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/gpio/pca953x_gpio.c b/drivers/gpio/pca953x_gpio.c index b0c66d18317..24b0732f89a 100644 --- a/drivers/gpio/pca953x_gpio.c +++ b/drivers/gpio/pca953x_gpio.c @@ -306,6 +306,7 @@ static int pca953x_probe(struct udevice *dev) struct pca953x_info *info = dev_get_plat(dev); struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev); char name[32], label[8], *str; + struct gpio_desc reset; int addr; ulong driver_data; int ret; @@ -321,6 +322,13 @@ static int pca953x_probe(struct udevice *dev)
driver_data = dev_get_driver_data(dev);
+ /* If a reset-gpios property is present, take the device out of reset. */ + ret = gpio_request_by_name(dev, "reset-gpios", 0, &reset, GPIOD_IS_OUT); + if (ret && ret != -ENOENT) { + dev_err(dev, "requesting reset-gpios failed: %d\n", ret); + return ret; + } + info->gpio_count = driver_data & PCA_GPIO_MASK; if (info->gpio_count > MAX_BANK * BANK_SZ) { dev_err(dev, "Max support %d pins now\n", MAX_BANK * BANK_SZ);
Hi Rasmus,
On 4/10/24 13:11, Rasmus Villemoes wrote:
The DT bindings for the pca953x family has an optional reset-gpios property. If present, ensure that the device is taken out of reset before attempting to read from it.
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk
drivers/gpio/pca953x_gpio.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/gpio/pca953x_gpio.c b/drivers/gpio/pca953x_gpio.c index b0c66d18317..24b0732f89a 100644 --- a/drivers/gpio/pca953x_gpio.c +++ b/drivers/gpio/pca953x_gpio.c @@ -306,6 +306,7 @@ static int pca953x_probe(struct udevice *dev) struct pca953x_info *info = dev_get_plat(dev); struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev); char name[32], label[8], *str;
- struct gpio_desc reset; int addr; ulong driver_data; int ret;
@@ -321,6 +322,13 @@ static int pca953x_probe(struct udevice *dev)
driver_data = dev_get_driver_data(dev);
- /* If a reset-gpios property is present, take the device out of reset. */
- ret = gpio_request_by_name(dev, "reset-gpios", 0, &reset, GPIOD_IS_OUT);
- if (ret && ret != -ENOENT) {
This seems to differ from the implementation we have for optionally getting gpios by index, c.f. https://elixir.bootlin.com/u-boot/latest/source/drivers/gpio/gpio-uclass.c#L...
""" struct gpio_desc *devm_gpiod_get_index(struct udevice *dev, const char *id, unsigned int index, int flags) { [...] rc = gpio_request_by_name(dev, propname, index, desc, flags);
end: [...] if (rc) return ERR_PTR(rc); [...] return desc; }
struct gpio_desc *devm_gpiod_get_index_optional(struct udevice *dev, const char *id, unsigned int index, int flags) { struct gpio_desc *desc = devm_gpiod_get_index(dev, id, index, flags);
if (IS_ERR(desc)) return NULL;
return desc; } """
It seems we only need to check whether rc is non-zero, but it doesn't check that it's not ENOENT. I think we would benefit from having the same logic here.
Also, maybe we need a devm_gpio_get_by_name_optional implementation in the subsystem so we don't have to reimplement it in drivers that want to use this?
Cheers, Quentin
On 10/04/2024 14.24, Quentin Schulz wrote:
Hi Rasmus,
@@ -321,6 +322,13 @@ static int pca953x_probe(struct udevice *dev) driver_data = dev_get_driver_data(dev); + /* If a reset-gpios property is present, take the device out of reset. */ + ret = gpio_request_by_name(dev, "reset-gpios", 0, &reset, GPIOD_IS_OUT); + if (ret && ret != -ENOENT) {
This seems to differ from the implementation we have for optionally getting gpios by index, c.f. https://elixir.bootlin.com/u-boot/latest/source/drivers/gpio/gpio-uclass.c#L...
""" struct gpio_desc *devm_gpiod_get_index(struct udevice *dev, const char *id, unsigned int index, int flags) { [...] rc = gpio_request_by_name(dev, propname, index, desc, flags);
end: [...] if (rc) return ERR_PTR(rc); [...] return desc; }
struct gpio_desc *devm_gpiod_get_index_optional(struct udevice *dev, const char *id, unsigned int index, int flags)
Well, that doesn't seem to have a lot of users outside tests? We really have way too many APIs for doing the same thing.
I copied the logic from some other driver that also had an optional reset-gpios and checked for -ENOENT, so I assumed that was the right thing to do.
{ struct gpio_desc *desc = devm_gpiod_get_index(dev, id, index, flags);
if (IS_ERR(desc)) return NULL;
return desc; } """
It seems we only need to check whether rc is non-zero, but it doesn't check that it's not ENOENT. I think we would benefit from having the same logic here.
What are you proposing exactly? That devm_gpiod_get_index_optional() starts propagating errors which are not -ENOENT? That would make sense, but requires that callers check three-ways (NULL, IS_ERR or valid), not just two-ways. Dunno.
Also, maybe we need a devm_gpio_get_by_name_optional implementation in the subsystem so we don't have to reimplement it in drivers that want to use this?
Maybe, but as I said, we already have too many helpers implemented in terms of each other with drivers using some random one even if there happens to be another helper that "helpfully" plugs in a 0 for the index or whatnot.
I'm unsure just exactly what I should do from here?
Rasmus
Hi Rasmus,
On 4/10/24 14:59, Rasmus Villemoes wrote:
On 10/04/2024 14.24, Quentin Schulz wrote:
Hi Rasmus,
@@ -321,6 +322,13 @@ static int pca953x_probe(struct udevice *dev) driver_data = dev_get_driver_data(dev); + /* If a reset-gpios property is present, take the device out of reset. */ + ret = gpio_request_by_name(dev, "reset-gpios", 0, &reset, GPIOD_IS_OUT); + if (ret && ret != -ENOENT) {
This seems to differ from the implementation we have for optionally getting gpios by index, c.f. https://elixir.bootlin.com/u-boot/latest/source/drivers/gpio/gpio-uclass.c#L...
""" struct gpio_desc *devm_gpiod_get_index(struct udevice *dev, const char *id, unsigned int index, int flags) { [...] rc = gpio_request_by_name(dev, propname, index, desc, flags);
end: [...] if (rc) return ERR_PTR(rc); [...] return desc; }
struct gpio_desc *devm_gpiod_get_index_optional(struct udevice *dev, const char *id, unsigned int index, int flags)
Well, that doesn't seem to have a lot of users outside tests? We really have way too many APIs for doing the same thing.
It is actually used outside of tests as well:
#define devm_gpiod_get_optional(dev, id, flags) \ devm_gpiod_get_index_optional(dev, id, 0, flags)
Then:
""" $ git grep devm_gpiod_get_optional drivers/phy/ti/phy-j721e-wiz.c: wiz->gpio_typec_dir = devm_gpiod_get_optional(dev, "typec-dir", drivers/power/pmic/pca9450.c: priv->sd_vsel_gpio = devm_gpiod_get_optional(dev, "sd-vsel", drivers/usb/dwc3/dwc3-generic.c: priv->ulpi_reset = devm_gpiod_get_optional(dev->parent, "reset", """
It's not THAT many but at least there are a few *real* users :)
Also, I think you actually want to use devm_gpiod_get_optional since it's basically just wrapping
""" gpio_request_by_name(dev, "reset-gpios", 0, &reset, GPIOD_IS_OUT); """
with devres?
-ENOENT seems to happen (at least) if the property reset-gpios isn't found, which very much would be the case if it's optional. Now it seems -EINVAL could also be returned in some cases... https://elixir.bootlin.com/u-boot/latest/source/drivers/core/of_access.c#L66...
Now... reading what the kernel does:
https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpiolib-devres.c...
checks the return value with https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpiolib.h#L189
Soooo... it seems they are doing what you're doing.
So, what I suggest is the following:
1) fix devm_gpiod_get_index_optional
to return desc (which may be a pointer or an ERR_PTR, so users should do an IS_ERR(desc) check after call) ONLY when NOT IS_ERR(desc) && PTR_ERR(desc) == -ENOENT.
So:
""" struct gpio_desc *devm_gpiod_get_index_optional(struct udevice *dev, const char *id, unsigned int index, int flags) { struct gpio_desc *desc = devm_gpiod_get_index(dev, id, index, flags);
if (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT) return NULL;
return desc; } """
Maybe some adding some new test also for this new part of the if check?
2) use devm_gpiod_get_optional in your driver
What do you think?
Cheers, Quentin
participants (2)
-
Quentin Schulz -
Rasmus Villemoes