[U-Boot] [PATCH] mmc: dw_mmc: reduce timeout detection cycle

[Ziyuan Xu <xzy.xu@rock-chips.com>]

Hi Jaehoon,

On 2016?07?19? 15:51, Jaehoon Chung wrote:
> Hi,
>
> On 07/19/2016 04:40 PM, Ziyuan Xu wrote:
>> Hi Jaehoon,
>>
>> On 2016?07?19? 12:22, Jaehoon Chung wrote:
>>> Hi Ziyuan,
>>>
>>> On 07/19/2016 11:33 AM, Ziyuan Xu wrote:
>>>> Hi Jaehoon,
>>>>
>>>> On 2016?07?19? 10:03, Jaehoon Chung wrote:
>>>>> Hi Ziyuan,
>>>>>
>>>>> On 07/19/2016 10:38 AM, Ziyuan Xu wrote:
>>>>>> It's no need to speed 10 seconds to wait the mmc device out from busy
>>>>>> status. 500 milliseconds enough.
>>>>> I agreed that 10 seconds is too big..
>>>>> Could you explain more how you get 500ms and feel enough?
>>>> Ordinarily, there are 3 types of scenarios that the mmc device was busy:
>>>> 1. The mmc interface didn't initialize (eg. gpio  iomux)
>>>> The device will be busy status until gpio iomux.
>>>>
>>>> 2. The last command with data transfer.
>>>> The maximum value of data timeout is 0xffffff cyles(see dwi databook Timeout Register), and the clock is up to 52MHZ under high speed mode.
>>>> timeout = 0xffffff * 1/52M = 0.32s
>>>>
>>>> 3. voltage switch
>>>> U-BOOT doesn't support voltage switch.
>>>>
>>>> In summary, I think 500 milliseconds is enough. What do you think?
>>> I think it's not important thing.
>>>
>>> This is for checking whether card is busy or not before sending command.
>>> I think it's not relevant to Timeout register. Just ensure that card is not busy before sending command.
>>> And there is no effect for I/O performance, isn't?
>> Yup,  I agree with you.  For scenarios 2, I mean that if the last command with data transfer, we will hit data_busy assertion probably. If the mmc device remains in a busy state more than 500ms, I think it may also be busy state after 10s.
>>> But 50ms is not bad. :) It's personal preference.
>> BTW, the timeout value is 500ms in kernel.
> Yep, it looks good to me. :)
> I have tested your patch with Exynos SoCs.
>
> Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
> Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Thanks for your test and review!
>
> Best Regards,
> Jaehoon Chung
>
>>> Best Regards,
>>> Jaehoon Chung
>>>
>>>>> Best Regards,
>>>>> Jaehoon Chung
>>>>>
>>>>>> Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
>>>>>> ---
>>>>>>
>>>>>>     drivers/mmc/dw_mmc.c | 2 +-
>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/mmc/dw_mmc.c b/drivers/mmc/dw_mmc.c
>>>>>> index 2cf7bae..790a166 100644
>>>>>> --- a/drivers/mmc/dw_mmc.c
>>>>>> +++ b/drivers/mmc/dw_mmc.c
>>>>>> @@ -195,7 +195,7 @@ static int dwmci_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd,
>>>>>>         ALLOC_CACHE_ALIGN_BUFFER(struct dwmci_idmac, cur_idmac,
>>>>>>                      data ? DIV_ROUND_UP(data->blocks, 8) : 0);
>>>>>>         int ret = 0, flags = 0, i;
>>>>>> -    unsigned int timeout = 100000;
>>>>>> +    unsigned int timeout = 500;
>>>>>>         u32 retry = 100000;
>>>>>>         u32 mask, ctrl;
>>>>>>         ulong start = get_timer(0);
>>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
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