drm/i915: fix freeze with blank screen booting highmem
authorHugh Dickins <hughd@google.com>
Tue, 22 Jul 2014 04:34:30 +0000 (21:34 -0700)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Tue, 22 Jul 2014 06:10:36 +0000 (08:10 +0200)
commit88b98287356762cc16c9ff6cd48116160a5d4dba
treeb5248a91d0cd20322944ec88ea01c807cc57772a
parenta0d036b074b4a5a933e37fcb9bdd6b3cc80a0387
drm/i915: fix freeze with blank screen booting highmem

x86_64 boots and displays fine, but booting x86_32 with CONFIG_HIGHMEM
has frozen with a blank screen throughout 3.16-rc on this ThinkPad T420s,
with i915 generation 6 graphics.

Fix 9d0a6fa6c5e6 ("drm/i915: add render state initialization"): kunmap()
takes struct page * argument, not virtual address.  Which the compiler
kindly points out, if you use the appropriate u32 *batch, instead of
silencing it with a void *.

Why did bisection lead decisively to nearby 229b0489aa75 ("drm/i915:
add null render states for gen6, gen7 and gen8")?  Because the u32
deposited at that virtual address by the previous stub failed the
PageHighMem test, and so did no harm.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/i915_gem_render_state.c