question: Why the nand_wait() wait for 20ms for nand program.

[Huang Shijie]

于 2013年01月21日 17:15, Matthieu CASTET 写道:
> Huang Shijie a écrit :
>>   于 2013年01月21日 16:57, Matthieu CASTET 写道:
>>> Huang Shijie a écrit :
>>>> 于 2013年01月18日 20:26, Matthieu CASTET 写道:
>>>>> Huang Shijie a écrit :
>>>>>> Hi all:
>>>>>> Why the nand_wait() wait for 20ms for nand program. could we
>>>>>> expand this time to 40ms? I have a nand chip : Micron MT29F64G08CBABAWP.
>>>>>> The chip's BUSY/READY pin may needs more then 20ms to become ready,
>>>>>> though its
>>>>>> datasheet tells me the tPROG's max value is 2.5ms.
>>>>>>
>>>>> Don't you have an hardware problem (missing pullup/down on ready busy pin) ?
>>>>>
>>>>> If the datasheet say the max value is 2.5 ms , how it can be more than 20 ms.
>>>> I finally found the root cause.
>>>>
>>>> I added the do_gettimeofday() in the nand_wait() to measure the
>>>> READY/BUSY time. The code is like this:
>>>> ---------------------------------------------------- code start
>>>>
>>> Could you dump jiffies and timeo in your code ?
>> The following just shows some part of the log:
>>
>> [my_nand_wait]status : 80,<21480, 21480>,<  665911, 664170>,<1, 1741>
>> [my_nand_wait]status : 80,<21480, 21480>,<  735989, 734626>,<1, 1363>
>> [my_nand_wait]status : 80,<21480, 21480>,<  805693, 804825>,<0, 868>
>>
>>  From the log, we can see that the kernel just waits for 1741us to break
>> the while loop,
>> not 20ms.
>>
> Yes but you should display jiffies and timeo value to understand why the kernel
> thinks 2 jiffies elapsed.
I dumpped the jiffies and timeo too. The jiffies is really _equal_ to 
the timeo, and then the while loop breaks.

thanks for your comments.

I think there is something wrong with the timer.

Huang Shijie





>
> Matthieu
>