On Mon, Feb 16, 2009 at 5:33 PM, Michel Dänzer <[email protected]> wrote:
> On Fri, 2009-02-13 at 10:27 -0800, Jesse Barnes wrote:
>> On Friday, February 13, 2009 2:33 am Michel Dänzer wrote:
>> > On Thu, 2009-02-12 at 09:15 -0800, Jesse Barnes wrote:
>> > > It does, but take a look at that code again.  If interrupts are disabled
>> > > by the timer, we'll capture the frame count.  If, sometime later, they're
>> > > re-enabled, we'll end up in drm_update_vblank_count.  And if, between
>> > > those two points, we've had a DPMS event, the frame counter will have
>> > > been reset and will now be a lower value, so our drm_update_vblank_count
>> > > will detect a wraparound.  I think any hardware that resets its frame
>> > > count will be susceptible to this problem unless we make wraparounds
>> > > harmless.
>> >
>> > The modeset ioctl makes wraparounds harmless if used correctly.
>>
>> I don't think it does.  And you may not be seeing this problem on radeon
>> because your max_vblank_count is only 0x1fffff, which wouldn't trigger this
>> behavior.
>
> Which btw looks like it's incorrect for newer Radeons with AVIVO display
> engine, which seem to have 24 bits in the frame counter registers -
> Dave/Alex?

Yes 24-bits on r500 and above.

Dave.

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