• Ben Widawsky's avatar
    drm/i915: Disable GGTT PTEs on GEN6+ suspend · 828c7908
    Ben Widawsky authored
    Once the machine gets to a certain point in the suspend process, we
    expect the GPU to be idle. If it is not, we might corrupt memory.
    Empirically (with an early version of this patch) we have seen this is
    not the case. We cannot currently explain why the latent GPU writes
    occur.
    
    In the technical sense, this patch is a workaround in that we have an
    issue we can't explain, and the patch indirectly solves the issue.
    However, it's really better than a workaround because we understand why
    it works, and it really should be a safe thing to do in all cases.
    
    The noticeable effect other than the debug messages would be an increase
    in the suspend time. I have not measure how expensive it actually is.
    
    I think it would be good to spend further time to root cause why we're
    seeing these latent writes, but it shouldn't preclude preventing the
    fallout.
    
    NOTE: It should be safe (and makes some sense IMO) to also keep the
    VALID bit unset on resume when we clear_range(). I've opted not to do
    this as properly clearing those bits at some later point would be extra
    work.
    
    v2: Fix bugzilla link
    
    Bugzilla: http://bugs.freedesktop.org/show_bug.cgi?id=65496
    Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=59321Tested-by: default avatarTakashi Iwai <tiwai@suse.de>
    Tested-by: default avatarPaulo Zanoni <paulo.r.zanoni@intel.com>
    Signed-off-by: default avatarBen Widawsky <ben@bwidawsk.net>
    Tested-By: default avatarTodd Previte <tprevite@gmail.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    828c7908
i915_reg.h 191 KB