Re: [PATCH v2 1/4] sh-pfc: do not call sh_pfc_get_pin_index() when unnecessary

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

Hi Sergei,

Thank you for the patch.

On Thursday 04 June 2015 16:25:01 Sergei Shtylyov wrote:
> Calling sh_pfc_get_pin_index()  to calculate a pin index based on the
> collected pin range data is unnecessary when we're dealing with
> 'pfc->info->pins' and 'chip->pins' arrays as those always reperesent the
> pins starting from index 0 sequentially. Being a  mere  optimization at
> this time, this change will become crucial when we'll allow the "holes" in
> those arrays...

Pin information is stored in per-SoC pins arrays (a.k.a. pfc->info->pins). The 
driver support two models to number pins:

- The sequential model, in which pins are numbered sequentially starting at 0. 
Pin numbers are equal to the index in the array.

- The explicit numbering model, in which each pin entry has an explicit number 
(stored in struct sh_pfc_pin.pin). Pins numbers are not necessarily equal to 
the index of the pin entry in the array.

The sh_pfc_get_pin_index() function converts a pin number to the pin index in 
the pins array.

Let's consider the sh_pfc_pinconf_validate() from which your patch removes the 
call to sh_pfc_get_pin_index() and uses the pin number directly. The function 
is called from the .pin_config_get() and .pin_config_set() handlers. One 
possible call path is

pinconf_pins_show() -> pinconf_dump_pin() -> pinconf_dump_pins() -> 
pinconf_generic_dump_pins() -> pinconf_generic_dump_one() -> 
pin_config_get_for_pin() -> .pin_config_get()

The pin value passed to the .pin_config_get() function is pctldev->desc-
>pins[i].number, which is the pin number, not its index. It thus looks like 
this patch introduces a bug.

There might be something obvious I'm not getting though, so please feel free 
to prove me wrong.

> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
> 
> ---
> Changes in version 2:
> - new patch.
> 
>  drivers/pinctrl/sh-pfc/gpio.c    |    6 ++----
>  drivers/pinctrl/sh-pfc/pinctrl.c |    7 +++----
>  2 files changed, 5 insertions(+), 8 deletions(-)
> 
> Index: linux-pinctrl/drivers/pinctrl/sh-pfc/gpio.c
> ===================================================================
> --- linux-pinctrl.orig/drivers/pinctrl/sh-pfc/gpio.c
> +++ linux-pinctrl/drivers/pinctrl/sh-pfc/gpio.c
> @@ -52,8 +52,7 @@ static void gpio_get_data_reg(struct sh_
>  			      struct sh_pfc_gpio_data_reg **reg,
>  			      unsigned int *bit)
>  {
> -	int idx = sh_pfc_get_pin_index(chip->pfc, offset);
> -	struct sh_pfc_gpio_pin *gpio_pin = &chip->pins[idx];
> +	struct sh_pfc_gpio_pin *gpio_pin = &chip->pins[offset];
> 
>  	*reg = &chip->regs[gpio_pin->dreg];
>  	*bit = gpio_pin->dbit;
> @@ -138,9 +137,8 @@ static int gpio_setup_data_regs(struct s
>  static int gpio_pin_request(struct gpio_chip *gc, unsigned offset)
>  {
>  	struct sh_pfc *pfc = gpio_to_pfc(gc);
> -	int idx = sh_pfc_get_pin_index(pfc, offset);
> 
> -	if (idx < 0 || pfc->info->pins[idx].enum_id == 0)
> +	if (pfc->info->pins[offset].enum_id == 0)
>  		return -EINVAL;
> 
>  	return pinctrl_request_gpio(offset);
> Index: linux-pinctrl/drivers/pinctrl/sh-pfc/pinctrl.c
> ===================================================================
> --- linux-pinctrl.orig/drivers/pinctrl/sh-pfc/pinctrl.c
> +++ linux-pinctrl/drivers/pinctrl/sh-pfc/pinctrl.c
> @@ -370,7 +370,7 @@ static int sh_pfc_gpio_request_enable(st
>  		/* If GPIOs are handled externally the pin mux type need to be
>  		 * set to GPIO here.
>  		 */
> -		const struct sh_pfc_pin *pin = &pfc->info->pins[idx];
> +		const struct sh_pfc_pin *pin = &pfc->info->pins[offset];
> 
>  		ret = sh_pfc_config_mux(pfc, pin->enum_id, PINMUX_TYPE_GPIO);
>  		if (ret < 0)
> @@ -410,7 +410,7 @@ static int sh_pfc_gpio_set_direction(str
>  	struct sh_pfc *pfc = pmx->pfc;
>  	int new_type = input ? PINMUX_TYPE_INPUT : PINMUX_TYPE_OUTPUT;
>  	int idx = sh_pfc_get_pin_index(pfc, offset);
> -	const struct sh_pfc_pin *pin = &pfc->info->pins[idx];
> +	const struct sh_pfc_pin *pin = &pfc->info->pins[offset];
>  	struct sh_pfc_pin_config *cfg = &pmx->configs[idx];
>  	unsigned long flags;
>  	unsigned int dir;
> @@ -452,8 +452,7 @@ static const struct pinmux_ops sh_pfc_pi
>  static bool sh_pfc_pinconf_validate(struct sh_pfc *pfc, unsigned int _pin,
>  				    enum pin_config_param param)
>  {
> -	int idx = sh_pfc_get_pin_index(pfc, _pin);
> -	const struct sh_pfc_pin *pin = &pfc->info->pins[idx];
> +	const struct sh_pfc_pin *pin = &pfc->info->pins[_pin];
> 
>  	switch (param) {
>  	case PIN_CONFIG_BIAS_DISABLE:

-- 
Regards,

Laurent Pinchart

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