[U-Boot] [PATCH v2] mmc: Split device init to decouple OCR-polling delay

[Simon Glass]

Hi,

On Fri, Nov 30, 2012 at 3:13 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Jaehoon,
>
> On Fri, Nov 30, 2012 at 12:25 AM, Jaehoon Chung <jh80.chung at samsung.com> wrote:
>> Hi,
>>
>> This concept is very good.
>> But I have one question. I think need to call mmc_init() one more, right?
>> how did you save the boot time(200ms)?
>>
>> On 11/29/2012 10:21 AM, Simon Glass wrote:
>>> From: Che-Liang Chiou <clchiou at chromium.org>
>>>
>>> Most of time that MMC driver spends on initializing a device is polling
>>> OCR (operation conditions register).  To decouple this polling loop,
>>> device init is split into two parts: The first part fires the OCR query
>>> command, and the second part polls the result.  So the caller is now no
>>> longer bound to the OCR-polling delay; he may fire the query, go
>>> somewhere and then come back later for the result.
>>>
>>> To use this, call mmc_set_preinit() on any device which needs this.
>>>
>>> This can save significant amounts of time on boot (e.g. 200ms) by
>>> hiding the MMC init time behind other init.
>> snip..
>>> +int mmc_init(struct mmc *mmc)
>>> +{
>>> +     int err = IN_PROGRESS;
>>> +     unsigned start = get_timer(0);
>>> +
>>> +     if (mmc->has_init)
>>> +             return 0;
>>> +     if (!mmc->init_in_progress)
>>> +             err = mmc_start_init(mmc);
>> It need not to return? if err is IN_PROGRESS, next condition is immediately run.
>> Then i think we didn't save the time before adjust this patch.
>
> It's a little confusing, but the way it works is that mmc_preinit()
> calls mmc_start_init() early in boot. Then when mmc_init() finally
> gets called (later) it finishes off the init. We still need mmc_init()
> to actually fully complete the init. If it were to return before
> completing the init then we would be unable to use the MMC.
>
>>> +
>>> +     if (!err || err == IN_PROGRESS)
>>> +             err = mmc_complete_init(mmc);
>>> +     debug("%s: %d, time %lu\n", __func__, err, get_timer(start));
>>>       return err;
>>>  }
>

Does this patch look good now? I am wondering if it will be including
in release, or in next?

Regards,
Simon

> [snip]
>
> Regards,
> Simon