Re: [PATCH 10/20] gpio: pca953x: Add optional reset gpio control

[Steve Longerbeam]

Hi Linus, Lothar,


On 12/30/2016 05:17 AM, Linus Walleij wrote:

On Thu, Dec 29, 2016 at 11:27 PM, Steve Longerbeam
 wrote:


Add optional reset-gpios pin control. If present, de-assert the
specified reset gpio pin to bring the chip out of reset.

Signed-off-by: Steve Longerbeam 
Cc: Linus Walleij 
Cc: Alexandre Courbot 
Cc: linux-g...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org

This seems like a separate patch from the other 19 patches so please send it
separately so I can handle logistics easier in the future.


Ok, I'll send the next version separately.





@@ -133,6 +134,7 @@ struct pca953x_chip {
 const char *const *names;
 unsigned long driver_data;
 struct regulator *regulator;
+   struct gpio_desc *reset_gpio;

Why do you even keep this around in the device state container?

As you only use it in the probe() function, use a local variable.

The descriptor will be free():ed by the devm infrastructure anyways.


I think my reasoning for putting the gpio handle into the device
struct was for possibly using it for run-time reset control at some
point. But that could be done later if needed, so I'll go ahead and
make it local.


+   /* see if we need to de-assert a reset pin */
+   chip->reset_gpio = devm_gpiod_get_optional(>dev,
+  "reset",
+  GPIOD_OUT_LOW);
+   if (IS_ERR(chip->reset_gpio)) {
+   dev_err(>dev, "request for reset pin failed\n");
+   return PTR_ERR(chip->reset_gpio);
+   }

Nice.


+   if (chip->reset_gpio) {
+   /* bring chip out of reset */
+   dev_info(>dev, "releasing reset\n");
+   gpiod_set_value(chip->reset_gpio, 0);
+   }

Is this really needed given that you set it low in the
devm_gpiod_get_optional()?


Yep, this is left over from a previous iteration, but it isn't needed now.
I'll remove it.

Steve

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Re: [PATCH 10/20] gpio: pca953x: Add optional reset gpio control

[Linus Walleij]

On Thu, Dec 29, 2016 at 11:27 PM, Steve Longerbeam
 wrote:

> Add optional reset-gpios pin control. If present, de-assert the
> specified reset gpio pin to bring the chip out of reset.
>
> Signed-off-by: Steve Longerbeam 
> Cc: Linus Walleij 
> Cc: Alexandre Courbot 
> Cc: linux-g...@vger.kernel.org
> Cc: linux-ker...@vger.kernel.org

This seems like a separate patch from the other 19 patches so please send it
separately so I can handle logistics easier in the future.


> @@ -133,6 +134,7 @@ struct pca953x_chip {
> const char *const *names;
> unsigned long driver_data;
> struct regulator *regulator;
> +   struct gpio_desc *reset_gpio;

Why do you even keep this around in the device state container?

As you only use it in the probe() function, use a local variable.

The descriptor will be free():ed by the devm infrastructure anyways.

> +   /* see if we need to de-assert a reset pin */
> +   chip->reset_gpio = devm_gpiod_get_optional(>dev,
> +  "reset",
> +  GPIOD_OUT_LOW);
> +   if (IS_ERR(chip->reset_gpio)) {
> +   dev_err(>dev, "request for reset pin 
> failed\n");
> +   return PTR_ERR(chip->reset_gpio);
> +   }

Nice.

> +   if (chip->reset_gpio) {
> +   /* bring chip out of reset */
> +   dev_info(>dev, "releasing reset\n");
> +   gpiod_set_value(chip->reset_gpio, 0);
> +   }

Is this really needed given that you set it low in the
devm_gpiod_get_optional()?

Yours,
Linus Walleij
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Re: [PATCH 10/20] gpio: pca953x: Add optional reset gpio control

[Lothar Waßmann]

Hi,

On Thu, 29 Dec 2016 14:27:25 -0800 Steve Longerbeam wrote:
> Add optional reset-gpios pin control. If present, de-assert the
> specified reset gpio pin to bring the chip out of reset.
> 
> Signed-off-by: Steve Longerbeam 
> Cc: Linus Walleij 
> Cc: Alexandre Courbot 
> Cc: linux-g...@vger.kernel.org
> Cc: linux-ker...@vger.kernel.org
> 
> ---
> 
> v2:
> - documented optional reset-gpios property in
>   Documentation/devicetree/bindings/gpio/gpio-pca953x.txt.
> ---
>  Documentation/devicetree/bindings/gpio/gpio-pca953x.txt |  4 
>  drivers/gpio/gpio-pca953x.c | 17 
> +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-pca953x.txt 
> b/Documentation/devicetree/bindings/gpio/gpio-pca953x.txt
> index 08dd15f..da54f4c 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio-pca953x.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio-pca953x.txt
> @@ -29,6 +29,10 @@ Required properties:
>   onsemi,pca9654
>   exar,xra1202
>  
> +Optional properties:
> + - reset-gpios: GPIO specification for the RESET input
> +
> +
>  Example:
>  
>  
> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> index d5d72d8..d1c0bd5 100644
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -22,6 +22,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  
>  #define PCA953X_INPUT0
>  #define PCA953X_OUTPUT   1
> @@ -133,6 +134,7 @@ struct pca953x_chip {
>   const char *const *names;
>   unsigned long driver_data;
>   struct regulator *regulator;
> + struct gpio_desc *reset_gpio;
>  
>   const struct pca953x_reg_config *regs;
>  
> @@ -756,6 +758,21 @@ static int pca953x_probe(struct i2c_client *client,
>   } else {
>   chip->gpio_start = -1;
>   irq_base = 0;
> +
> + /* see if we need to de-assert a reset pin */
> + chip->reset_gpio = devm_gpiod_get_optional(>dev,
> +"reset",
> +GPIOD_OUT_LOW);

> + if (IS_ERR(chip->reset_gpio)) {
> + dev_err(>dev, "request for reset pin failed\n");
> + return PTR_ERR(chip->reset_gpio);
> + }
> +
> + if (chip->reset_gpio) {
> + /* bring chip out of reset */
> + dev_info(>dev, "releasing reset\n");
> + gpiod_set_value(chip->reset_gpio, 0);
>
The pin is already initialized to the inactive state thru the
GPIOD_OUT_LOW flag in devm_gpiod_get_optional(), so this call to
gpiod_set_value() is useless.


Lothar Waßmann
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