linux-kernel - Re: [PATCH v2 2/3] mmc: dw_mmc: Use mmc_regulator_set_vqmmc in start_signal_voltage

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Date:	Mon, 15 Dec 2014 15:44:24 -0800
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Mark Brown <broonie@...nel.org>,
	Alexandru Stan <amstan@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Chris Ball <chris@...ntf.net>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] mmc: dw_mmc: Use mmc_regulator_set_vqmmc in start_signal_voltage_switch

Hi Doug,

On Mon, Dec 15, 2014 at 3:25 PM, Doug Anderson <dianders@...omium.org> wrote:
> We've introduced a new helper in the MMC core:
> mmc_regulator_set_vqmmc().  Let's use this in dw_mmc.  Using this new
> helper has some advantages:
>
> 1. We get the mmc_regulator_set_vqmmc() behavior of trying to match
>    VQMMC and VMMC when the signal voltage is 3.3V.  This ensures max
>    compatibility.
>
> 2. We get rid of a few more warnings when probing unsupported
>    voltages.
>
> 3. We get rid of some non-dw_mmc specific code in dw_mmc.
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>

One small comment below...

> @@ -1170,24 +1168,11 @@ static int dw_mci_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
>          */
>         uhs = mci_readl(host, UHS_REG);
>         if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
> -               min_uv = 2700000;
> -               max_uv = 3600000;
>                 uhs &= ~v18;
>         } else {
> -               min_uv = 1700000;
> -               max_uv = 1950000;
>                 uhs |= v18;
>         }
> -       if (!IS_ERR(mmc->supply.vqmmc)) {
> -               ret = regulator_set_voltage(mmc->supply.vqmmc, min_uv, max_uv);
> -
> -               if (ret) {
> -                       dev_dbg(&mmc->class_dev,
> -                                        "Regulator set error %d: %d - %d\n",
> -                                        ret, min_uv, max_uv);
> -                       return ret;
> -               }
> -       }
> +       mmc_regulator_set_vqmmc(mmc, ios);

Shouldn't we check the return value here and bail out of the voltage
switch procedure if it fails?
--
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