[U-Boot] [PATCH] [Timer]Remove calls to [get, reset]_timer outside arch/

[J. William Campbell]

On 5/23/2011 1:10 PM, Graeme Russ wrote:
> On 24/05/11 04:29, Scott McNutt wrote:
>> Hi Bill,
>>
>> J. William Campbell wrote:
>>> On 5/23/2011 6:12 AM, Scott McNutt wrote:
>>>> Dear Graeme,
>>>>
>>>> Graeme Russ wrote:
>>>>> On 23/05/11 22:19, Scott McNutt wrote:
>>>>>> Hi Graeme,
>>>>>>
>>>>>> Graeme Russ wrote:
>>>>>>> There is no need to use get_timer() and reset_timer() and there are
>>>>>>> build
>>>>>> I must have missed something WRT reset_timer() -- my apologies
>>>>>> if I'm covering old ground.
>>>>>>
>>>>>> When the timestamp is incremented using an interrupt that occurs with
>>>>>> a period greater than 1 ms, we can get early timeouts. reset_timer()
>>>>>> solved the problem. What's the recommended approach for dealing with
>>>>>> this without reset_timer() ?
>>> Hi Scott,
>>>            Are you saying that the interrupt frequency is greater than
>>> 1000 times per second, or as I read it, the frequency is less than 1000
>>> per second (period greater than 1 ms). If anything, that should make the
>>> timer run slow, not fast.
>>>   I wonder if it is a resolution issue. What are the typical delays in ms
>>> you are using?
>> Some older nios2 implementations have _fixed_ 10 msec timers.
>> Basically, the timestamp is incremented asynchronous to get_timer(0).
>> So a  10 msec timeout can occur, for example, almost immediately if
>> the timer isn't reset just prior to calling get_timer(0). There are
>> more details in the comments for the following commits:
>>
>> nios2: Reload timer count in reset_timer():
>>    d8bc0a2889700ba063598de6d4e7d135360b537e
>>
>> cfi_flash: reset timer in flash status check:
>>    22d6c8faac4e9fa43232b0cf4da427ec14d72ad3
>>
>> I'm totally in favor of cleaning this stuff up. It caused some
>> headaches (and wasted time) about 13 months ago. My primary concern
>> is to avoid breaking things that currently work for us nios2
>> weenies ... at least for any length of time.
>>
>> Things are a bit tight for me until next week or so. I'll probably
>> come up for air around June 1st ... and I'll be glad to help out.
>>
> Is there any reason why we cannot silently perform a reset_timer() any time
> set_timer() is called with a parameter of 0?
Hi All,
      I assume you mean get_timer(0)?  In principle, you cannot do this 
because it could be inside another get_timer(0) loop that has already 
some time elapsed before you hit the inner get_timer(0). I think what 
needs to happen on the old NIOS with 10 ms resolution on the interrupt 
times is that all timer intervals must have 10 ms added and then rounded 
up to the nearest multiple of 10. Thus, if you wanted to wait for 1 
millisecond, you must use an argument of 20 ms to be sure you wait at 
all! If you use an argument of 10, it won't help because you could get 
an interrupt right away and exit. If these routines are nios2 specific, 
you could add a local reset_timer, but I assume they are generic. . Note 
that if these routines are not nios2 specific, is there any harm in 
waiting "too long"?

Best Regards,
Bill Campbell
> Regards,
>
> Graeme
>
>