From mboxrd@z Thu Jan  1 00:00:00 1970
From: Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH 1/3] mmc: core: Remove power_restore bus_ops for mmc and
 sd
Date: Thu, 04 Apr 2013 14:44:17 +0300
Message-ID: <515D6791.4010803@intel.com>
References: <1362142035-8403-1-git-send-email-ulf.hansson@stericsson.com> <1362142035-8403-2-git-send-email-ulf.hansson@stericsson.com> <515D3DCC.8000505@intel.com> <CAPDyKFr983eazpW=ky2knujur+RND4m0nL=n1pZmUyzxVSe3uA@mail.gmail.com>
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To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Ulf Hansson <ulf.hansson@stericsson.com>, linux-mmc <linux-mmc@vger.kernel.org>, Chris Ball <cjb@laptop.org>, Johan Rudholm <johan.rudholm@stericsson.com>

On 04/04/13 12:55, Ulf Hansson wrote:
> On 4 April 2013 10:46, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> On 01/03/13 14:47, Ulf Hansson wrote:
>>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>>
>>> The mmc_power_restore|save_host API is only used by SDIO func drivers. SDIO
>>
>> NAK - it is also used by eMMC hardware reset i.e. mmc_do_hw_reset()
> 
> True for eMMC, but for SD card the bus_ops can go away. Thanks for
> spotting this Adrian!
> 
> Although, I see some serious problems with the mmc_do_hw_reset
> function - it could cause eMMC data corruption.
> 
> Issuing hw reset and doing re-initialization by using the mmc
> bus_ops->power_restore will mean no consideration is taken to "cache
> ctrl", "bkops" and "power off notify". I think it must.
> 
> So the more proper way instead of calling power_restore, should be to
> use bus_ops->suspend and bus_ops->resume callbacks from the
> mmc_do_hw_reset function. Additionally if bus_ops->suspend is done
> successfully, we should be able to skip the actual hw reset and just
> do bus_ops->resume.
> 
> Do you have any thoughts on this?

Certainly the bootloader should leave the eMMC is a safe state including:
flushing the cache or turning it off (why did it turn on?), stopping
background operations (why did it start them?), disabling power-off
notification CMD0? (again why it it enable it?)

Note that according to spec. CMD0 anyway clears the cache so you have lost
your data anyway.