linux-kernel - Re: [PATCH v2 2/5] mmc: mediatek: Add Mediatek MMC driver

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Date:	Fri, 17 Apr 2015 11:37:44 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	Chaotian Jing <chaotian.jing@...iatek.com>,
	Mark Rutland <mark.rutland@....com>,
	James Liao <jamesjj.liao@...iatek.com>,
	Arnd Bergmann <arnd@...db.de>,
	srv_heupstream <srv_heupstream@...iatek.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Hongzhou Yang <hongzhou.yang@...iatek.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Bin Zhang (章斌) <bin.zhang@...iatek.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Chris Ball <chris@...ntf.net>,
	Will Deacon <will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	linux-mediatek@...ts.infradead.org,
	Sascha Hauer <kernel@...gutronix.de>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"Joe.C" <yingjoe.chen@...iatek.com>,
	Eddie Huang <eddie.huang@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 2/5] mmc: mediatek: Add Mediatek MMC driver

On 17 April 2015 at 11:12, Sascha Hauer <s.hauer@...gutronix.de> wrote:
> Ulf,
>
> On Tue, Mar 31, 2015 at 02:23:06PM +0200, Ulf Hansson wrote:
>> On 17 March 2015 at 04:13, Chaotian Jing <chaotian.jing@...iatek.com> wrote:
>> > +
>> > +       msdc_set_buswidth(host, ios->bus_width);
>> > +
>> > +       /* Suspend/Resume will do power off/on */
>> > +       switch (ios->power_mode) {
>> > +       case MMC_POWER_UP:
>> > +               msdc_init_hw(host);
>> > +               if (!IS_ERR(mmc->supply.vmmc)) {
>> > +                       ret = mmc_regulator_set_ocr(mmc, mmc->supply.vmmc,
>> > +                                       ios->vdd);
>> > +                       if (ret) {
>> > +                               dev_err(host->dev, "Failed to set vmmc power!\n");
>> > +                               return;
>> > +                       }
>> > +               }
>> > +               break;
>> > +       case MMC_POWER_ON:
>> > +               if (!IS_ERR(mmc->supply.vqmmc)) {
>> > +                       ret = regulator_enable(mmc->supply.vqmmc);
>>
>> The calls to regulator_enable|disable() for the vqmmc will not be
>> balanced properly here. You need a local cache variable like
>> "is_enabled" to keep track of this.
>
> Shouldn't the MMC core provide balanced hooks for this? What about
> MMC_POWER_UP, can this be used for enabling regulators?

Currently host drivers deals with vqmmc enabling/disabling, setting
voltage, etc - entirely by them selves.

Dough Anderson is working on fixing that:
http://lkml.iu.edu/hypermail/linux/kernel/1503.1/03108.html

MMC_POWER_UP is when vmmc shall be enabled.

MMC_POWER_ON is when vqmmc shall be enabled.

Kind regards
Uffe
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