From: Pierre Ossman <drzeus-mmc@drzeus.cx>
To: Madhusudhan C <madhu_lkml@yahoo.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: mmc select voltage functionality
Date: Mon, 26 Nov 2007 18:46:17 +0100 [thread overview]
Message-ID: <20071126184617.04029484@poseidon.drzeus.cx> (raw)
In-Reply-To: <655340.80743.qm@web44811.mail.sp1.yahoo.com>
On Thu, 22 Nov 2007 05:34:11 -0800 (PST)
Madhusudhan C <madhu_lkml@yahoo.com> wrote:
> Hi Pierre,
>
> I have a question on the mmc_select_voltage fn of the mmc core file drivers/mmc/core/core.c.
>
> During the power up sequence the mmc_power_up fn sets the OCR bit to setup 3V. Subsequentely the mmc_select_voltage fn selects the lowest voltage
> the card can support.The host->ios.power_mode is not changed to MMC_POWER_UP before calling mmc_set_ios from this function hence the power_mode remains in MMC_POWER_ON state.So my question is, how should the controller driver handle this change in volatge. Under which case of power mode should the controller driver change the voltage again when a dual voltage card is detected?
>
To be completely correct, the MMC layer should probably power down the card first, yes. Right now most drivers will handle all of these things as they see fit. Haven't seen a single bug report about it yet so...
Just change the voltage in whatever way makes sense for your controller.
Rgds
--
-- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org
PulseAudio, core developer http://pulseaudio.org
rdesktop, core developer http://www.rdesktop.org
parent reply other threads:[~2007-11-26 17:46 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <655340.80743.qm@web44811.mail.sp1.yahoo.com>]
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