[U-Boot] [RFC] ARM timing code refactoring

[Andreas Bießmann]

Hi Albert,

Am 24.01.2011 12:58, schrieb Albert ARIBAUD:
> Hi Andreas,
> 
> Le 24/01/2011 09:25, Andreas Bießmann a écrit :
> 
>>> That's where I come back to one point of my proposal: if we can get a
>>> general framework for get_timer() to return a 64-bit free-running tick
>>> value, then we might not need a ms-based get_time() at all, because we
>>> could use get_timer() as well for ms timings, provided we can convert
>>> our timeout from ms to ticks, i.e.
>>>
>>>     /* let's wait 200 milliseconds */
>>>     /* Timing loop uses ticks: convert 200 ms to 'timeout' ticks */
>>>     timeout = ms_to_ticks(200);
>>>     u32 start = get_timer(); /* start time, in ticks */
>>>     do {
>>>         ...
>>>     } while ( (get_timer() -start)<  timeout);
>>
>> You may think about the following change to this proposal:
>>
>> /* lets wait 200 ms */
>> /* get the end point of our timeout in ticks */
>> u64 timeout_end = get_timer() + ms_to_ticks(200);
>> do {
>>   ...
>> } while ( get_timer()<  timeout_end);
> 
> The problem here is that in the loop exit condition you replace a
> difference between two unsigned times (which always yields the correct
> duration) with a comparison of two dates (which does not).

Ok, I got your point.

regards

Andreas Bießmann