linux-kernel - Re: [PATCH v2 10/22] mmc: tmio: support IP-builtin card detection logic

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Date:   Wed, 6 Dec 2017 00:03:29 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        linux-renesas-soc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v2 10/22] mmc: tmio: support IP-builtin card detection logic

2017-12-05 0:13 GMT+09:00 Wolfram Sang <wsa@...-dreams.de>:
>> +static int tmio_mmc_get_cd(struct mmc_host *mmc)
>> +{
>> +     struct tmio_mmc_host *host = mmc_priv(mmc);
>> +     int ret;
>> +
>> +     ret = mmc_gpio_get_cd(mmc);
>> +     if (ret >= 0)
>> +             return ret;
>> +
>> +     return !!(sd_ctrl_read16_and_16_as_32(host, CTL_STATUS) &
>> +                                                     TMIO_STAT_SIGSTATE);
>> +}


I just followed tmio_mmc_get_ro() implementation.

If we do not care the symmetry between _get_ro() and _get_cd() hooks,
yes, your suggestion makes sense.



> I wonder if we shouldn't do something like:
>
>         if (mmc_can_gpio_cd())
>                 return mmc_gpio_get_cd()
>         else
>                 return !!(sd_ctrl_read16_and_16_as_32...)
>
> If we have a GPIO CD defined, I think we want the value of
> mmc_gpio_get_cd() in all cases. It makes clearer that this is an
> 'either-or' case and not a fallback mechanism.
>


Another possibility would select this in _probe().
We would need to evaluate mmc_can_gpio_cd() only once when probing.

I will follow your suggestion, though.
Either way is fine with me.



static int tmio_mmc_get_cd(struct mmc_host *mmc)
{
       struct tmio_mmc_host *host = mmc_priv(mmc);

       return !!(sd_ctrl_read16_and_16_as_32(host, CTL_STATUS) &
                                                TMIO_STAT_SIGSTATE);
}

static const struct mmc_host_ops tmio_mmc_ops = {
      ...
      .get_cd      = tmio_mmc_get_cd,
      ...
};

int tmio_mmc_host_probe( ... )
{
      ....

      /* replace get_cd hook when we use GPIO for card detection */
      if (mmc_can_gpio_cd(mmc))
                _host->ops.get_cd = mmc_gpio_get_cd;


}





-- 
Best Regards
Masahiro Yamada