RE: [PATCH 1/3] mmc: dw_mmc: use mmc_regulator_get_supply to handle regulators

From: Seungwon Jeon <tgih.jun@samsung.com>
To: 'Doug Anderson' <dianders@chromium.org>
Cc: 'Jaehoon Chung' <jh80.chung@samsung.com>,
	'Yuvaraj Kumar C D' <yuvaraj.cd@gmail.com>,
	'linux-samsung-soc' <linux-samsung-soc@vger.kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	'Chris Ball' <cjb@laptop.org>,
	linux-mmc@vger.kernel.org, 'Ulf Hansson' <ulf.hansson@linaro.org>,
	'Sonny Rao' <sonnyrao@chromium.org>,
	'Tomasz Figa' <t.figa@samsung.com>,
	'Kukjin Kim' <kgene.kim@samsung.com>,
	'sunil joshi' <joshi@samsung.com>,
	ks.giri@samsung.com, 'Prashanth G' <prashanth.g@samsung.com>,
	'Alim Akhtar' <alim.akhtar@samsung.com>,
	'Yuvaraj Kumar C D' <yuvaraj.cd@samsung.com>
Subject: RE: [PATCH 1/3] mmc: dw_mmc: use mmc_regulator_get_supply to handle regulators
Date: Thu, 26 Jun 2014 19:30:52 +0900	[thread overview]
Message-ID: <004f01cf9129$b4ac9690$1e05c3b0$%jun@samsung.com> (raw)
In-Reply-To: <CAD=FV=UCinFuZQW+_GYFw=M046ziTLRNvvHUvsx_GQ0kjw5DfQ@mail.gmail.com>

Hi Doug,

On Thu, June 26, 2014, Doug Anderson wrote:
> Seungwon,
> 
> On Wed, Jun 25, 2014 at 4:18 AM, Seungwon Jeon <tgih.jun@samsung.com> wrote:
> >> >> +       case MMC_POWER_ON:
> >> >> +               if (!IS_ERR(mmc->supply.vqmmc) &&
> >> >> +                               !test_bit(DW_MMC_IO_POWERED, &slot->flags)) {
> > You can use regulator_is_enabled() instead of flag bit, DW_MMC_IO_POWERED.
> 
> I'd be a little worried about regulator_is_enabled() since regulators
> are reference counted.  What if someone else is sharing this
> regulator?  The regulator might happen to be enabled when you check it
> but unless you add your own dw_mmc reference count they might turn it
> off.
Cool, that's a possibility. Some assumption may need.
If mmc's core can guarantee its balance, I think we don't need to consider some flag.

Thanks,
Seungwon Jeon
> 
> > Important thing is that if powering vmmc failed at MMC_POWER_UP, vqmmc should not be powered.
> 
> Good point.
> --
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