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SubjectRe: [PATCH 1/3] drm: Widen vblank count to 64 bits. Change vblank time precision to ns
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On 07/07/17 10:34 AM, Michel Dänzer wrote:
> On 07/07/17 12:04 AM, Keith Packard wrote:
>> Michel Dänzer <michel@daenzer.net> writes:
>>
>>>> @@ -317,6 +317,9 @@ int via_driver_irq_postinstall(struct drm_device *dev)
>>>> if (!dev_priv)
>>>> return -EINVAL;
>>>>
>>>> + if (dev->driver->get_vblank_counter)
>>>> + dev->max_vblank_count = 0xffffffff;
>>>
>>> What's the purpose of this? All drivers providing get_vblank_counter
>>> should already initialize max_vblank_count correctly.
>>
>> Yeah, I couldn't prove that this driver did that,
>
> Which driver?
>
>> and as Daniel says, we haven't ever audited the drivers to make sure
>> they do.
>
> I don't think that's what he meant, rather that with the change above,
> all drivers have to be audited to make sure the added assignment doesn't
> clobber an earlier assignment by the driver.

... and if there are any drivers that set
dev->driver->get_vblank_counter but don't set dev->max_vblank_count to a
non-0 value, that the hardware counter actually has 32 bits.


I'd say don't bother, just drop this hunk.


--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer

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