[Intel-gfx] [PATCH 2/2] drm/i915: wait for IPS_ENABLE when enabling IPS

[Paulo Zanoni]

2013/9/20 Daniel Vetter <daniel at ffwll.ch>:
> On Thu, Sep 19, 2013 at 09:24:33PM +0100, Chris Wilson wrote:
>> On Thu, Sep 19, 2013 at 05:03:06PM -0300, Paulo Zanoni wrote:
>> > From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>> >
>> > At the end of haswell_crtc_enable we have an intel_wait_for_vblank
>> > with a big comment, and the message suggests it's a workaround for
>> > something we don't really understand. So I removed that wait and
>> > started getting HW state readout error messages saying that the IPS
>> > state is not what we expected.
>> >
>> > I investigated and concluded that after you write IPS_ENABLE to
>> > IPS_CTL, the bit will only actually become 1 on the next vblank. So
>> > add code to wait for the IPS_ENABLE bit. We don't really need this
>> > wait right now due to the wait I already mentioned, but at least this
>> > one has a reason to be there, while the other one is just to
>> > workaround some problem: we may remove it in the future.
>> >
>> > The wait also acts as a POSTING_READ which we missed.
>> >
>> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>
>> Both patches:
>> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
>>
>> I was thinking that maybe the intel_wait_for_vblank would be better from
>> a documenting perspective - and it would also give warnings for trying
>> to enable ips whilst the pipe was off. But you would still need the wait
>> for IPS_ENABLE as confirmation anyway.
>
> Both queued for -next, thanks for the patches&review.

Hmmm, this patch depends on the "enable planes only after the pipe is
really running" patch. Due to that missing patch, now I get
"[drm:hsw_enable_ips] *ERROR* Timed out waiting for IPS enable" when
booting. I should have said this, sorry :(

I

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Paulo Zanoni