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From: Ulf Hansson <ulf.hansson@linaro.org>
To: Doug Anderson <dianders@chromium.org>
Cc: Heiko Stuebner <heiko@sntech.de>,
	Jaehoon Chung <jh80.chung@samsung.com>,
	Seungwon Jeon <tgih.jun@samsung.com>,
	Mark Brown <broonie@kernel.org>,
	Alexandru Stan <amstan@chromium.org>,
	Alim Akhtar <alim.akhtar@samsung.com>,
	Sonny Rao <sonnyrao@chromium.org>,
	Andrew Bresticker <abrestic@chromium.org>,
	Addy Ke <addy.ke@rock-chips.com>,
	Javier Martinez Canillas <javier.martinez@collabora.co.uk>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Chris Ball <chris@printf.net>,
	Johan Rudholm <johan.rudholm@axis.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Tim Kryger <tim.kryger@gmail.com>,
	Andrew Gabbasov <andrew_gabbasov@mentor.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	linux-mmc <linux-mmc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc()
Date: Mon, 16 Mar 2015 15:05:59 +0100	[thread overview]
Message-ID: <CAPDyKFq_WMJfqNGuxwN7xPmhv2X6-+G1zXpdD6zYDkDe7-Jo2A@mail.gmail.com> (raw)
In-Reply-To: <1426112117-18220-2-git-send-email-dianders@chromium.org>

On 11 March 2015 at 23:15, Doug Anderson <dianders@chromium.org> wrote:
> This adds logic to the MMC core to set VQMMC.  This is expected to be
> called by MMC drivers like dw_mmc as part of (or instead of) their
> start_signal_voltage_switch() callback.
>
> A few notes:
>
> * When setting the signal voltage to 3.3V we do our best to make VQMMC
>   and VMMC match.  It's been reported that this makes some old cards
>   happy since they were tested back in the day before UHS when VQMMC
>   and VMMC were provided by the same regulator.  A nice side effect of
>   this is that we don't end up on the hairy edge of VQMMC (2.7V),
>   which some EEs claim is a little too close to the minimum for
>   comfort.
>
> * When setting the signal voltage to 1.8V or 1.2V we aim for that
>   specific voltage instead of picking the lowest one in the range.
>
> * We very purposely don't print errors in mmc_regulator_set_vqmmc().
>   There are cases where the MMC core will try several different
>   voltages and we don't want to pollute the logs.
>
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
> ---
> Changes in v4: None
> Changes in v3: None
> Changes in v2:
> - Now use existing regulator_set_voltage_tol() function.
>
>  drivers/mmc/core/core.c  | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mmc/host.h |  7 +++++++
>  2 files changed, 58 insertions(+)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 23f10f7..1d3b84e 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1394,6 +1394,57 @@ int mmc_regulator_set_ocr(struct mmc_host *mmc,
>  }
>  EXPORT_SYMBOL_GPL(mmc_regulator_set_ocr);
>
> +static int mmc_regulator_set_voltage_if_supported(struct regulator *regulator,
> +                                                 int new_uV, int tol_uV)
> +{
> +       /*
> +        * Check if supported first to avoid errors since we may try several
> +        * signal levels during power up and don't want to show errors.
> +        */
> +       if (!regulator_is_supported_voltage_tol(regulator, new_uV, tol_uV))
> +               return -EINVAL;
> +
> +       return regulator_set_voltage_tol(regulator, new_uV, tol_uV);
> +}
> +
> +/**
> + * mmc_regulator_set_vqmmc - Set VQMMC as per the ios
> + *
> + * For 3.3V signaling, we try to match VQMMC to VMMC as closely as possible.
> + * That will match the behavior of old boards where VQMMC and VMMC were supplied
> + * by the same supply.  The Bus Operating conditions for 3.3V signaling in the
> + * SD card spec also define VQMMC in terms of VMMC.
> + *
> + * For 1.2V and 1.8V signaling we'll try to get as close as possible to the
> + * requested voltage.  This is definitely a good idea for UHS where there's a
> + * separate regulator on the card that's trying to make 1.8V and it's best if
> + * we match.
> + *
> + * This function is expected to be used by a controller's
> + * start_signal_voltage_switch() function.
> + */
> +int mmc_regulator_set_vqmmc(struct mmc_host *mmc, struct mmc_ios *ios)
> +{
> +       /* If no vqmmc supply then we can't change the voltage */
> +       if (IS_ERR(mmc->supply.vqmmc))
> +               return -EINVAL;
> +
> +       switch (ios->signal_voltage) {
> +       case MMC_SIGNAL_VOLTAGE_120:
> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
> +                       1200000, 100000);

Is 1V the lowest possible value? How did you get to that?

> +       case MMC_SIGNAL_VOLTAGE_180:
> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
> +                       1800000, 100000);

Is 1V the lowest possible value? How did you get to that?

> +       case MMC_SIGNAL_VOLTAGE_330:
> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
> +                       regulator_get_voltage(mmc->supply.vmmc), 300000);

Why 3V? Shouldn't it be 2.7V? How will else those SoC that for example
supports 2.9V only work?

> +       default:
> +               return -EINVAL;
> +       }
> +}
> +EXPORT_SYMBOL_GPL(mmc_regulator_set_vqmmc);
> +
>  #endif /* CONFIG_REGULATOR */
>
>  int mmc_regulator_get_supply(struct mmc_host *mmc)
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 0c8cbe5..edd7d59 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -416,6 +416,7 @@ int mmc_regulator_get_ocrmask(struct regulator *supply);
>  int mmc_regulator_set_ocr(struct mmc_host *mmc,
>                         struct regulator *supply,
>                         unsigned short vdd_bit);
> +int mmc_regulator_set_vqmmc(struct mmc_host *mmc, struct mmc_ios *ios);
>  #else
>  static inline int mmc_regulator_get_ocrmask(struct regulator *supply)
>  {
> @@ -428,6 +429,12 @@ static inline int mmc_regulator_set_ocr(struct mmc_host *mmc,
>  {
>         return 0;
>  }
> +
> +static inline int mmc_regulator_set_vqmmc(struct mmc_host *mmc,
> +                                         struct mmc_ios *ios)
> +{
> +       return -EINVAL;
> +}
>  #endif
>
>  int mmc_regulator_get_supply(struct mmc_host *mmc);

One more thought,s as for the vmmc regulator we have a
"regulator_enabled" member in the mmc_host. Should we add a similar
member for vqmmc? That would prevent host drivers from keeping track
of this state themselves.

Kind regards
Uffe

> --
> 2.2.0.rc0.207.ga3a616c
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

  reply	other threads:[~2015-03-16 14:06 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-11 22:15 [PATCH v4 1/4] mmc: dw_mmc: Don't try to enable the CD until we're sure we're not deferring Doug Anderson
2015-03-11 22:15 ` [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc() Doug Anderson
2015-03-16 14:05   ` Ulf Hansson [this message]
2015-03-16 15:12     ` Doug Anderson
2015-03-17 10:23       ` Ulf Hansson
2015-03-17 10:38         ` Mark Brown
2015-03-17 11:28           ` Ulf Hansson
2015-03-19  4:09         ` Doug Anderson
2015-03-19 11:14           ` Ulf Hansson
2015-03-19 11:36             ` Mark Brown
2015-03-20 10:55               ` Ulf Hansson
2015-03-20 11:28                 ` Mark Brown
2015-04-07 20:05                   ` Doug Anderson
2015-04-08 11:28                     ` Mark Brown
2015-03-11 22:15 ` [PATCH v4 3/4] mmc: dw_mmc: Use mmc_regulator_set_vqmmc in start_signal_voltage_switch Doug Anderson
2015-03-11 22:15 ` [PATCH v4 4/4] ARM: dts: Specify VMMC and VQMMC on rk3288-evb Doug Anderson
2015-03-11 23:30   ` Heiko Stuebner
2015-04-07 21:37     ` Heiko Stübner
2015-03-13 11:32 ` [PATCH v4 1/4] mmc: dw_mmc: Don't try to enable the CD until we're sure we're not deferring Jaehoon Chung
2015-03-13 12:10   ` Heiko Stuebner
2015-03-16  2:09     ` Jaehoon Chung
2015-03-27  5:55 ` Jaehoon Chung
2015-03-27 15:46   ` Doug Anderson

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