[Intel-gfx] [PATCH] drm/i915: check the power wells on assert_{cursor, plane}

[Daniel Vetter]

On Thu, Jul 17, 2014 at 2:53 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
> 2014-07-17 5:38 GMT-03:00 Daniel Vetter <daniel at ffwll.ch>:
>> On Wed, Jul 16, 2014 at 05:06:34PM -0300, Paulo Zanoni wrote:
>>> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>>
>>> Since we merged runtime PM support for DPMS, it is possible that these
>>> functions will be called when the power wells are disabled but a mode
>>> is "set", resulting in "failed assertion" and "device suspended while
>>> reading register" WARNs.
>>>
>>> To reproduce the bug: disable all screens using mode unset, do a
>>> modeset on one screen, disable it using DPMS, then try to do a mode
>>> unset on it again to see the WARNs.
>>>
>>> Testcase: igt/rpm_rpm/dpms-mode-unset-lpsp
>>> Testcase: igt/rpm_rpm/dpms-mode-unset-non-lpsp
>>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>
>> Hm, where do we call these asserts while the pipe is off? Do you have some
>> example backtraces at hand?
>
> Function __intel_set_mode() directly calls intel_crtc_disable(), which
> calls both assert_plane_disabled() and assert_cursor_disabled().

Hm, I think it makes more sense to drop the three asserts in there.
The modeset state checker will already notice when we've failed to
turn off the pipe. And we check cursors and plane state in the enable
sequence, too.

Since we use these asserts a lot to lock down the precise modeset
sequence I actually prefer if they're a bit dumb and don't check the
power wells.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch