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Date: Mon, 21 Jan 2013 10:15:40 +0100
From: Matthieu CASTET <matthieu.castet@parrot.com>
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To: Huang Shijie <b32955@freescale.com>
Subject: Re: question: Why the nand_wait() wait for 20ms for nand program.
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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.


Matthieu