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    SubjectRe: [git pull] drm merge for 3.9-rc1
    On Tue, Feb 26, 2013 at 05:39:46PM -0800, Linus Torvalds wrote:
    > On Mon, Feb 25, 2013 at 4:05 PM, Dave Airlie <airlied@linux.ie> wrote:
    > >
    > > Highlights:
    > >
    > > i915: all over the map, haswell power well enhancements, valleyview macro horrors cleaned up, killing lots of legacy GTT
    > > code,
    >
    > Lowlight:
    >
    > There's something wrong with i915 DP detection or whatever. I get
    > stuff like this:
    >
    > [ 5.710827] [drm:intel_dp_aux_wait_done] *ERROR* dp aux hw did not
    > signal timeout (has irq: 1)!
    > [ 5.720810] [drm:intel_dp_aux_wait_done] *ERROR* dp aux hw did not
    > signal timeout (has irq: 1)!
    > [ 5.730794] [drm:intel_dp_aux_wait_done] *ERROR* dp aux hw did not
    > signal timeout (has irq: 1)!
    > [ 5.740782] [drm:intel_dp_aux_wait_done] *ERROR* dp aux hw did not
    > signal timeout (has irq: 1)!
    > [ 5.750775] [drm:intel_dp_aux_wait_done] *ERROR* dp aux hw did not
    > signal timeout (has irq: 1)!
    > [ 5.750778] [drm:intel_dp_aux_ch] *ERROR* dp_aux_ch not done status
    > 0xa145003f
    > .....
    > [ 8.149931] [drm:intel_dp_aux_ch] *ERROR* dp_aux_ch not done status
    > 0xa145003f
    >
    > and after that the screen ends up black.
    >
    > It's happened twice now, but is not 100% repeatable. It looks like the
    > message itself is new, but the black screen is also new and does seem
    > to happen when I get the message, so...
    >
    > The second time I touched the power button, and the machine came back.
    > Apparently the suspend/resume cycle made it all magically work: the
    > suspend caused the same errors, but then the resume made it all good
    > again.
    >
    > Some kind of missed initialization at bootup? It's not reliable enough
    > to bisect, but I obviously suspect commit 9ee32fea5fe8 ("drm/i915:
    > irq-drive the dp aux communication") since that is where the message
    > was added..
    >
    > Btw, looking at that commit, what do you think the semantics of the
    > timeout in something like
    >
    > done = wait_event_timeout(dev_priv->gmbus_wait_queue, C, 10);
    >
    > would be? What's that magic "10"? It's some totally random number.
    >
    > Guys, it should be something meaningful. If you meant a tenth of a
    > second, use HZ/10 or something. Because just the plain "10" is crazy.
    > I happen to have CONFIG_HZ_1000=y, and you're apparently waiting for a
    > hundreth of a second. Was that what you intended? Because if it was,
    > it is still crap, since CONFIG_HZ might be 100, and then you're
    > waiting for ten times longer.
    >
    > IOW, passing in a random number like that is crazy. It cannot possibly
    > be right.
    >
    > I have no idea whether the timeout has anything to do with anything,
    > but it reinforces my suspicion that there is something wrong with that
    > commit.

    Ok, I've merged two patches from Paulo, one to fixup the harmless jiffies
    vs. msec confusion. And the other to plug a race in our irq handler which
    did lead to missed dp aux interrupts according to some digging done by
    Imre. The important patch is the current tip of

    git://people.freedesktop.org/~danvet/drm-intel drm-intel-fixes

    44498aea293b37af1d463acd9658cdce1ecdf427 drm/i915: also disable south interrupts when handling them

    Just in case you want to give it a quick whirl. Since the failed dp aux
    transaction caused the resume modeset to fail for you (resulting in the
    black screen) I hope that this should fix both issues.

    I'll forward the pull to Dave in a few days since atm I'm stalling a bit
    for confirmation on another little regression fix. And there's nothing
    earth-shattering in my -fixes queue right now.

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


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