[Intel-gfx] [PATCH 2/2] drm/i915: Limit the busy wait on requests to 2us not 10ms!

[Tvrtko Ursulin]

On 16/11/15 12:55, Chris Wilson wrote:
> On Mon, Nov 16, 2015 at 12:08:08PM +0000, Tvrtko Ursulin wrote:
>>
>> On 16/11/15 11:12, Chris Wilson wrote:
>>> On Mon, Nov 16, 2015 at 10:24:45AM +0000, Tvrtko Ursulin wrote:
>>>> On 15/11/15 13:32, Chris Wilson wrote:
>>>>> +static u64 local_clock_us(unsigned *cpu)
>>>>> +{
>>>>> +	u64 t;
>>>>> +
>>>>> +	*cpu = get_cpu();
>>>>> +	t = local_clock() >> 10;
>>>>
>>>> Needs comment I think to explicitly mention the approximation, or
>>>> maybe drop the _us suffix?
>>>
>>> I did consider _approx_us but thought that was overkill. A comment along
>>> the lines of
>>> /* Approximately convert ns to us - the error is less than the
>>>   * truncation!
>>>   */
>>
>> And the result is not used in subsequent calculations apart from
>> comparing against an approximate timeout?
>
> Exactly, the timeout is fairly arbitrary and defined in the same units.
> That we truncate is a much bigger cause for concern in terms of spinning
> accurately for a definite length of time.

Bah sorry that was not supposed to be a question but a suggestion to add 
to the comment. Must had mistyped the question mark. :)

Regards,

Tvrtko