linux-kernel - Re: [PATCH] mmc: dw_mmc: try pick the exact same voltage as vmmc for vqmmc

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Date:	Fri, 21 Nov 2014 09:42:08 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	addy ke <addy.ke@...k-chips.com>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	"tgih.jun@...sung.com" <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Chris Ball <chris@...ntf.net>,
	Dinh Nguyen <dinguyen@...era.com>,
	Heiko Stübner <heiko@...ech.de>,
	Olof Johansson <olof@...om.net>,
	Sonny Rao <sonnyrao@...omium.org>,
	Alexandru Stan <amstan@...omium.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"zhenfu.fang" <zhenfu.fang@...k-chips.com>,
	Eddie Cai <cf@...k-chips.com>, lintao <lintao@...k-chips.com>,
	chenfen <chenfen@...k-chips.com>, zyf <zyf@...k-chips.com>,
	Jianqun Xu <xjq@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Chris Zhong <zyw@...k-chips.com>,
	姚智情 <yzq@...k-chips.com>,
	han jiang <hj@...k-chips.com>,
	Kever Yang <kever.yang@...k-chips.com>,
	zhangqing <zhangqing@...k-chips.com>,
	Lin Huang <hl@...k-chips.com>
Subject: Re: [PATCH] mmc: dw_mmc: try pick the exact same voltage as vmmc for vqmmc

Ulf,

On Fri, Nov 21, 2014 at 4:06 AM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> [...]
>
>> Sure
>> If the first card is sd2.0 since startup, dw_mci_switch_voltage will not be called,
>
> That can't be right. mmc_power_up() should trigger
> dw_mci_switch_voltage() to be invoked.

Hmmm, I think you're right.  Addy: can you double check if it's only
the 2nd card for you?  I was thinking that if a regulator is currently
3.3V and you request 2.7 - 3.3V the regulator framework will treat
that as a noop.  ...but that definitely doesn't appear to be the case.
When I boot up the first time even with no SD card plugged in, I see
this at bootup:

[    3.042234] vccio_sd: 1800 <--> 3300 mV at 3300 mV

...showing that it started at 3.3V.  Then I see:

$ grep "" /sys/class/regulator/regulator.16/{name,microvolts}
/sys/class/regulator/regulator.16/name:vccio_sd
/sys/class/regulator/regulator.16/microvolts:2700000

...so it is certainly getting changed even with no card plugged in.


BTW: I don't actually have one of these failing cards--all of mine
work.  Addy, do you know the make and model of the card you have that
fails?


-Doug
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