Re: [PATCH] mmc: core: Optimize boot time by detecting cards simultaneously

[Shawn Lin <shawn.lin@rock-chips.com>]

On 2015/12/18 9:28, Jaehoon Chung wrote:
> Hi,
>
> On 12/18/2015 06:49 AM, Ulf Hansson wrote:
>> On 17 December 2015 at 20:47, Alan Cooper <alcooperx@gmail.com> wrote:
>>> On Wed, Dec 16, 2015 at 4:07 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>>> To find the improved card detection times, I just used the kernel boot
>>>> log and checked the time stamps for when the cards get detected. I ran
>>>> the tests ~10 times and picked up some average values.
>>>>
>>>> To notice the improvement you need at least two cards to be inserted
>>>> during boot. Perhaps you have a platform with one eMMC and one SD card
>>>> slot, you can test.
>>>
>>> I tested the patch on one of our ARM bases SoC's. The SoC has an SD
>>> card slot on the first controller and an eMMC device on the second
>>> controller. I found ~100ms improvement on the time it took for the
>>> rootfs on the eMMC device to be ready for use. Interestingly, I did
>>> see the SD/eMMC order swap once in 20 tries. This is not an issue for
>>> us as we already have to use UUID for the eMMC rootfs in case an SD
>>> card is installed.
>>>

hi Ulf,
     I'm interested in this patch since I also spent a little time 
optimzing the boot time and sequence for my local branch based on kernel 
3.1x. With you patch, it seems, the tablet only achieves very small 
improvement for the SD controller(less than 20ms).

My test environment:
Kernel: 3.14
Slot: 1 emmc(1st) + 1 SD card(2nd) + 1 sdio card(3rd)

I happen to run massive reboot test for my stable kernel branch this 
weekend, so I will apply this patch to see if any problem occurs. :)



>>> Al
>>
>> Al, thanks for your effort in testing. I assume I can apply a
>> tested-by tag for that!
>>
>> BTW, if you want to see an even better improvement, just find a
>> crappier SD card as I guess you have a quite good one. :-)
>
> I didn't test with this yet..actually, i have tested with only one board(Exynos4412).
> There is no the changing index. (Not too much for testing)
> but in my experiment, our platform(Tizen) should be produced the problem in SD-card case.
> I need to check with SystemFW guys. I will check this..ASAP.
>
> Best Regards,
> Jaehoon Chung
>
>>
>> Kind regards
>> Uffe
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>


-- 
Best Regards
Shawn Lin