Re: [PATCH 1/3] mmc: core: Remove power_restore bus_ops for mmc and sd

Adrian Hunter
2013-04-04T11:54:58Z

On 04/04/13 14:52, Ulf Hansson wrote:
> On 4 April 2013 13:44, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> 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?)
>
> Not sure what you mean here. What has a booloader to do with this?

When do you think hw reset is used?

>
>>
>> Note that according to spec. CMD0 anyway clears the cache so you have lost
>> your data anyway.
>
> What I am saying that we can try send "cache ctrl" and "power off
> notify" before we send CMD0 / do hw reset. The no data shall be lost.

With an uninitialized bus? Or an unresponsive card?