From: Chris Wilson <chris@chris-wilson.co.uk>
To: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, stable@vger.kernel.org
Subject: Re: [PATCH] drm/i915: fix overlay on i830M
Date: Mon, 22 Oct 2012 11:54:05 +0100 [thread overview]
Message-ID: <eeac1e$4ngd7v@AZSMGA002.ch.intel.com> (raw)
In-Reply-To: <1350902658-1956-1-git-send-email-daniel.vetter@ffwll.ch>
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On Mon, 22 Oct 2012 12:44:18 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> The overlay on the i830M has a peculiar failure mode: It works the
> first time around after boot-up, but consistenly hangs the second time
> it's used.
>
> Chris Wilson has dug out a nice errata:
>
> "1.5.12 Clock Gating Disable for Display Register
> Address Offset: 06200h–06203h
>
> "Bit 3
> Ovrunit Clock Gating Disable.
> 0 = Clock gating controlled by unit enabling logic
> 1 = Disable clock gating function
> DevALM Errata ALM049: Overlay Clock Gating Must be Disabled: Overlay
> & L2 Cache clock gating must be disabled in order to prevent device
> hangs when turning off overlay.SW must turn off Ovrunit clock gating
> (6200h) and L2 Cache clock gating (C8h)."
>
> Now I've nowhere found that 0xc8 register and hence couldn't apply the
> l2 cache workaround. But I've remembered that part of the magic that
> the OVERLAY_ON/OFF commands are supposed to do is to rearrange cache
> allocations so that the overlay scaler has some scratch space.
>
> And while pondering how that could explain the hang the 2nd time we
> enable the overlay, I've remembered that the old ums overlay code did
> _not_ issue the OVERLAY_OFF cmd.
>
> And indeed, disabling the OFF cmd results in the overlay working
> flawlessly, so I guess we can workaround the lack of the above
> workaround by simply never disabling the overlay engine once it's
> enabled.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47827
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
That looks fun, and indeed will probably work. So if we never issue the
OFF command, do we still need i830_init_clock_gating()?
And if we do still need i830_init_clock_gating() wouldn't it be better
applied as a quirk to intel_overlay_on()?
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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next prev parent reply other threads:[~2012-10-22 10:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-22 10:44 [PATCH] drm/i915: fix overlay on i830M Daniel Vetter
2012-10-22 10:54 ` Chris Wilson [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-10-22 10:55 Daniel Vetter
2012-10-23 9:12 ` Daniel Vetter
2012-10-23 9:56 ` Chris Wilson
2012-10-23 10:59 ` Daniel Vetter
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