tree db6296c490af826669c964c65fb6a34d4476dfcf
parent 163f53a2611c98a9f8e25cbda30ce8ce268b92de
author Jesse Barnes <jbarnes@virtuousgeek.org> 1412884663 -0700
committer Daniel Vetter <daniel.vetter@ffwll.ch> 1414161249 +0200

drm/i915: preserve swizzle settings if necessary v4

Some machines (like MBAs) might use a tiled framebuffer but not enable
display swizzling at boot time.  We want to preserve that configuration
if possible to prevent a boot time mode set.  On IVB+ it shouldn't
affect performance anyway since the memory controller does internal
swizzling anyway.

For most other configs we'll be able to enable swizzling at boot time,
since the initial framebuffer won't be tiled, thus we won't see any
corruption when we enable it.

v2: preserve swizzling if BIOS had it set (Daniel)
v3: preserve swizzling only if we inherited a tiled framebuffer (Daniel)
    check display swizzle setting in detect_bit_6_swizzle (Daniel)
    use gen6 as cutoff point (Daniel)
v4: fixup swizzle preserve again, had wrong init order (Daniel)

Reported-by: Kristian Høgsberg <hoegsberg@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>