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    SubjectRe: [BISECTED] agp/intel: revert "Remove confusion of stolen entries not stolen memory"
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    On Monday 20 December 2010 22:06:47 Chris Wilson wrote:
    > On Mon, 20 Dec 2010 21:52:38 +0100, Arnd Bergmann <arnd@arndb.de> wrote:
    > > On Monday 20 December 2010 20:52:07 Chris Wilson wrote:
    > > >
    > > > Also, which modules do you have loaded when using VESA? i.e. is the
    > > > i915.ko loaded, but in UMS mode (i915.modeset=0)?
    > >
    > > This doesn't seem to matter, as far as I can tell, i915 can be loaded
    > > or now.
    >
    > Thanks, that rules out the likely explanation that we [i915] loaded the
    > GTT with some conflicting entries. Instead it is likely the initialisation
    > of the GTT to point to the scratch page that is triggering the problem.
    > Can you try disabling it with:
    >
    > diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
    > index 356f73e..238848e 100644
    > --- a/drivers/char/agp/intel-gtt.c
    > +++ b/drivers/char/agp/intel-gtt.c
    > @@ -867,11 +867,13 @@ static int intel_fake_agp_configure(void)
    >
    > agp_bridge->gart_bus_addr = intel_private.gma_bus_addr;
    >
    > +#if 0
    > for (i = 0; i < intel_private.base.gtt_total_entries; i++) {
    > intel_private.driver->write_entry(intel_private.scratch_page_dma,
    > i, 0);
    > }
    > readl(intel_private.gtt+i-1); /* PCI Posting. */
    > +#endif
    >
    > global_cache_flush();

    Yes, this works as well, good catch!

    > > I've seen the system crash once while loading i915 with
    > > modeset=1 and my revert patch applied and backed it out.
    > >
    > > After that, I could no longer even get i915 to do modesetting,
    > > the ioremap in intel_opregion_setup now fails because reserve_memtype
    > > decides that the opregion should be write-back when we ask for
    > > an uncached mapping. That's probably an unrelated problem, but
    > > I'm mentioning it anyway in case it's significant.
    >
    > I hope not. But it sounds like we're in for a turbulent ride if ioremap is
    > failing in -next.

    It only fails for the opregion. I feel I've done enough bisecting for today,
    but it's certainly broken in -next and the ioremap works in 2.6.37-rc6.
    Should the opregion actually be writeback cached? Maybe something is
    wrong in reserve_memtype.

    Loading i915 in -rc6 also crashes my system hard when modeset=1, but
    that may be a hardware problem -- the same one that used to cause occasional
    hangs with i915 KMS, forcing me to run X11 with the vesa driver.

    Arnd


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