linux-kernel - Re: [PATCH 3/4] mmc: sdhci: defer probing on regulator_get

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Message-ID: <CAL1qeaH19h3D49C3O3qQ+GtWSeOdu79TQTZGfj9dC-+-G1c3kA@mail.gmail.com>
Date:	Tue, 15 Apr 2014 12:44:02 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Tim Kryger <tim.kryger@...aro.org>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	linux-tegra@...r.kernel.org,
	ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	mike.looijmans@...ic.nl
Subject: Re: [PATCH 3/4] mmc: sdhci: defer probing on regulator_get_optional() failures

On Tue, Apr 15, 2014 at 12:03 PM, Tim Kryger <tim.kryger@...aro.org> wrote:
> On Mon, Apr 14, 2014 at 6:42 PM, Andrew Bresticker
> <abrestic@...omium.org> wrote:
>> If regulator_get_optional() returns EPROBE_DEFER, it indicates
>> that the regulator may show up later (e.g. the DT property is
>> present but the corresponding regulator may not have probed).
>> Instead of continuing without the regulator, return EPROBE_DEFER
>> from sdhci_add_host().  Also, fix regulator leaks in the error
>> paths in sdhci_add_host().
>>
>> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
>> ---
>>  drivers/mmc/host/sdhci.c | 19 ++++++++++++++++---
>>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> This appears to be an improvement on Mike Looijmans patch:
>
> https://lkml.org/lkml/2014/4/7/34
>
> The regulator_put() calls are appropriate but I wonder if we should
> take this a step farther.  Ulf is sure to point out that
> mmc_regulator_get_supply() can be used to get regulators (though it
> does stuff the pointers in host->mmc->supply.vmmc/vqmmc instead of
> host->vmmc/vqmmc).  However, that function doesn't put back the
> reference to vmmc if the request for vqmmc returns EPROBE_DEFER.  If
> it did, it believe it could be used here to simplify the error
> handling as all the regulator checks would happen up front.  What do
> you think?

Seems reasonable.  The put()s aren't necessary with
mmc_regulator_get_supply() since it uses the devm_* API, however it
doesn't return an error in case of EPROBE_DEFER when getting vqmmc,
which is what we want in this case.

>
> -Tim
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