From: Ulf Hansson <ulf.hansson@stericsson.com>
To: Jassi Brar <jaswinder.singh@linaro.org>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>,
Liam Girdwood <lrg@slimlogic.co.uk>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Mattias WALLIN <mattias.wallin@stericsson.com>,
Jonas ABERG <jonas.aberg@stericsson.com>,
Lee Jones <lee.jones@linaro.org>
Subject: Re: [PATCH] regulator: core: Keep boot_on regulators powered during init
Date: Wed, 25 Apr 2012 17:44:30 +0200 [thread overview]
Message-ID: <4F981BDE.4050906@stericsson.com> (raw)
In-Reply-To: <CAJe_Zhd9gUJX05=q9Zjb5QX_SBtPYMBxDz5Gu+=H+GWt97Rf9w@mail.gmail.com>
On 04/25/2012 05:34 PM, Jassi Brar wrote:
>> On Mon, Apr 23, 2012 at 02:45:10PM +0200, Ulf Hansson wrote:
>>
>>> If the platform already have booted from the eMMC card, the card is
>>> already powered an initialized from a bootloader. Cutting the power
>>> without first notifying the card by sending commands to it, must be
>>> prevented and also violates the eMMC specification. In the end, it
>>> will mean that the detect and initialization procedure fails.
>>
> Shouldn't the bootloader be responsible for ensuring MMC is
> put down after using it and before passing control to the kernel.
This is kind of complicated. eMMC is powered by two regulators. VCC and
VCCQ. Cutting VCC uncontrolled is not allowed. If doing so anyway there
is two options to recover.
1. Cut VCCQ as well and do full reinit of the eMMC
2. Pull a hw-reset pin to the eMMC and do a full reinit of the eMMC.
In some cases neither is possible due to HW constraints. Thus we have to
make sure VCC is not cut.
>
> Even if the bootloader didn't power off properly, unless there is
> some outstanding data to be written when the kernel is passed
> control, perhaps it's not that serious?
The kernel will not be to re-init the eMMC... quite serious. :-)
Kind regards
Ulf Hansson
next prev parent reply other threads:[~2012-04-25 15:44 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 9:37 [PATCH] regulator: core: Keep boot_on regulators powered during init Ulf Hansson
2012-04-23 10:18 ` Mark Brown
2012-04-23 10:52 ` Ulf Hansson
2012-04-23 11:05 ` Mark Brown
2012-04-23 12:21 ` Ulf Hansson
2012-04-23 12:25 ` Mark Brown
2012-04-23 12:45 ` Ulf Hansson
2012-04-23 18:01 ` Mark Brown
2012-04-24 8:09 ` Ulf Hansson
2012-04-24 10:56 ` Mark Brown
2012-04-24 12:43 ` Ulf Hansson
2012-04-25 8:02 ` Mark Brown
2012-04-25 9:37 ` Ulf Hansson
2012-04-25 9:58 ` Mark Brown
2012-04-25 16:45 ` Jassi Brar
2012-04-25 15:34 ` Jassi Brar
2012-04-25 15:44 ` Ulf Hansson [this message]
2012-04-25 16:31 ` Jassi Brar
2012-04-26 8:35 ` Mark Brown
2012-04-26 9:10 ` Jassi Brar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4F981BDE.4050906@stericsson.com \
--to=ulf.hansson@stericsson.com \
--cc=broonie@opensource.wolfsonmicro.com \
--cc=jaswinder.singh@linaro.org \
--cc=jonas.aberg@stericsson.com \
--cc=lee.jones@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lrg@slimlogic.co.uk \
--cc=mattias.wallin@stericsson.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.