linux-kernel - Re: [PATCH 1/3] pinctrl: sunxi: Add support for fetching pinconf settings from hardware

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Message-ID: <CAGb2v65BAx9EHhuyM-85F2vD+tXeiakLs8CQYuQOBVsVn=+BTw@mail.gmail.com>
Date:   Tue, 4 Oct 2016 23:49:27 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH 1/3] pinctrl: sunxi: Add support for fetching pinconf
 settings from hardware

On Tue, Oct 4, 2016 at 4:02 PM, Maxime Ripard
<maxime.ripard@...e-electrons.com> wrote:
> On Tue, Oct 04, 2016 at 09:51:10AM +0800, Chen-Yu Tsai wrote:
>> The sunxi pinctrl driver only caches whatever pinconf setting was last
>> set on a given pingroup. This is not particularly helpful, nor is it
>> correct.
>>
>> Fix this by actually reading the hardware registers and returning
>> the correct results or error codes. Also filter out unsupported
>> pinconf settings. Since this driver has a peculiar setup of 1 pin
>> per group, we can support both pin and pingroup pinconf setting
>> read back with the same code. The sunxi_pconf_reg helper and code
>> structure is inspired by pinctrl-msm.
>>
>> With this done we can also claim to support generic pinconf, by
>> setting .is_generic = true in pinconf_ops.
>>
>> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>> ---
>>  drivers/pinctrl/sunxi/pinctrl-sunxi.c | 85 +++++++++++++++++++++++++++++++++--
>>  1 file changed, 82 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.c b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
>> index 54455af566ec..609843c9a65c 100644
>> --- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c
>> +++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
>> @@ -10,6 +10,7 @@
>>   * warranty of any kind, whether express or implied.
>>   */
>>
>> +#include <dt-bindings/pinctrl/sun4i-a10.h>
>>  #include <linux/io.h>
>>  #include <linux/clk.h>
>>  #include <linux/gpio/driver.h>
>> @@ -269,15 +270,91 @@ static const struct pinctrl_ops sunxi_pctrl_ops = {
>>       .get_group_pins         = sunxi_pctrl_get_group_pins,
>>  };
>>
>> +static int sunxi_pconf_reg(unsigned pin, enum pin_config_param param,
>> +                        u32 *offset, u32 *shift, u32 *mask)
>> +{
>> +     switch (param) {
>> +     case PIN_CONFIG_DRIVE_STRENGTH:
>> +             *offset = sunxi_dlevel_reg(pin);
>> +             *shift = sunxi_dlevel_offset(pin);
>> +             *mask = DLEVEL_PINS_MASK;
>> +             break;
>> +
>> +     case PIN_CONFIG_BIAS_PULL_UP:
>> +     case PIN_CONFIG_BIAS_PULL_DOWN:
>> +     case PIN_CONFIG_BIAS_DISABLE:
>> +             *offset = sunxi_pull_reg(pin);
>> +             *shift = sunxi_pull_offset(pin);
>> +             *mask = PULL_PINS_MASK;
>> +             break;
>> +
>> +     default:
>> +             return -ENOTSUPP;
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static int sunxi_pconf_get(struct pinctrl_dev *pctldev, unsigned pin,
>> +                        unsigned long *config)
>> +{
>> +     struct sunxi_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev);
>> +     enum pin_config_param param = pinconf_to_config_param(*config);
>> +     u32 offset, shift, mask, val;
>> +     u16 arg;
>> +     int ret;
>> +
>> +     pin -= pctl->desc->pin_base;
>> +
>> +     ret = sunxi_pconf_reg(pin, param, &offset, &shift, &mask);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     val = (readl(pctl->membase + offset) >> shift) & mask;
>> +
>> +     switch (pinconf_to_config_param(*config)) {
>> +     case PIN_CONFIG_DRIVE_STRENGTH:
>> +             arg = (val + 1) * 10;
>> +             break;
>> +
>> +     case PIN_CONFIG_BIAS_PULL_UP:
>> +             if (val != SUN4I_PINCTRL_PULL_UP)
>> +                     return -EINVAL;
>> +             arg = 1; /* hardware is weak pull-up */
>> +             break;
>> +
>> +     case PIN_CONFIG_BIAS_PULL_DOWN:
>> +             if (val != SUN4I_PINCTRL_PULL_DOWN)
>> +                     return -EINVAL;
>> +             arg = 1; /* hardware is weak pull-down */
>> +             break;
>> +
>> +     case PIN_CONFIG_BIAS_DISABLE:
>> +             if (val != SUN4I_PINCTRL_NO_PULL)
>> +                     return -EINVAL;
>> +             arg = 0;
>> +             break;
>> +
>> +     default:
>> +             /* sunxi_pconf_reg should catch anything unsupported */
>> +             WARN_ON(1);
>> +             return -ENOTSUPP;
>
> This should be EINVAL. The operation is supported, but one of the
> argument is not valid.

According to include/linux/pinctrl/pinconf.h

 * @pin_config_get: get the config of a certain pin, if the requested config
 *      is not available on this controller this should return -ENOTSUPP
 *      and if it is available but disabled it should return -EINVAL

So I think it is correct to return -ENOTSUPP here.

ChenYu