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    SubjectRe: [2/2] 2.6.21-rc7: known regressions
    On Mon, Apr 16, 2007 at 03:16:37AM +0200, Adrian Bunk wrote:
    > On Sun, Apr 15, 2007 at 08:54:46PM -0400, Dave Jones wrote:
    > > On Mon, Apr 16, 2007 at 02:37:23AM +0200, Adrian Bunk wrote:
    > >
    > > > Subject : ThinkPad X60: resume no longer works (PCI related?)
    > > > workaround: booting with "hpet=disable"
    > > > References :
    > > > Submitter : Dave Jones <>
    > > > Jeremy Fitzhardinge <>
    > > > Caused-By : PCI merge
    > > > commit 78149df6d565c36675463352d0bfe0000b02b7a7
    > > > Handled-By : Eric W. Biederman <>
    > > > Rafael J. Wysocki <>
    > > > Status : unknown
    > >
    > > note that this workaround doesn't seem to work in all cases.
    > > Mine may a slightly different model (I have the tablet version)
    > > but disabling hpet shows the same regression.
    > > I've been fighting Eric's USB debug cable code in the hope
    > > of getting _something_ useful out of it other than a black screen,
    > > but I've been getting nowhere with it.
    > I'm not sure why I thought you two ran into the same regression.

    I'm not sure why I never hit the same bug that Jeremy did
    (again, maybe subtle hardware differences between our models),
    but I finally got somewhere. -rc7 with the same config I've
    been testing exhibited exactly the same bug. Disabling
    the FB_BACKLIGHT option (and all the FB drivers that 'select' it),
    I get a working display on resume again.

    This makes a lot of sense. As before, when I resumed, the backlight
    wasn't coming back on, but I knew the machine was alive, as
    capslock was working. (Amusingly, I never noticed the backlight
    wasn't coming back on until tonight, when I started debugging this
    with the lights off. Late-night debugging ftw).

    I'll try and narrow down exactly where it's failing in the
    backlight code next, but it's getting late here, so I may
    leave this until tomorrow for further investigation.
    Some other clues for anyone playing along at home:
    This X60 has Intel graphics. ie, I'm not using any of
    the drivers that 'select FB_BACKLIGHT', so somewhere in
    the common fb code is code that I'm guessing is dependant
    upon the framebuffer driver doing something or other
    if FB_BACKLIGHT is set.

    (Adding Richard to Cc: as he seems to be responsible for
    the FB backlight code from what I can tell.)


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