From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>,
Paulo Zanoni <przanoni@gmail.com>,
intel-gfx@lists.freedesktop.org,
Paulo Zanoni <paulo.r.zanoni@intel.com>
Subject: Re: [PATCH 2/2] drm/i915: wait for IPS_ENABLE when enabling IPS
Date: Fri, 20 Sep 2013 10:12:32 +0200 [thread overview]
Message-ID: <20130920081232.GI32145@phenom.ffwll.local> (raw)
In-Reply-To: <20130919202433.GC7745@nuc-i3427.alporthouse.com>
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@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@intel.com>
>
> Both patches:
> Reviewed-by: Chris Wilson <chris@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.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
next prev parent reply other threads:[~2013-09-20 8:12 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-19 20:03 [PATCH 0/2] Small IPS fixes Paulo Zanoni
2013-09-19 20:03 ` [PATCH 1/2] drm/i915: POSTING_READ IPS_CTL before waiting for the vblank Paulo Zanoni
2013-09-19 20:03 ` [PATCH 2/2] drm/i915: wait for IPS_ENABLE when enabling IPS Paulo Zanoni
2013-09-19 20:24 ` Chris Wilson
2013-09-20 8:12 ` Daniel Vetter [this message]
2013-09-20 15:18 ` Paulo Zanoni
2013-09-20 21:49 ` Daniel Vetter
2013-10-08 21:02 ` Paulo Zanoni
2013-10-08 21:58 ` Daniel Vetter
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