drm/i915: Acquire dpio_lock for VLV sideband programming in DP/HDMI
Otherwise we get flooded by the kernel warning us that we are doing long sequences of IO without serialisation. For example, WARNING: CPU: 0 PID: 11136 at drivers/gpu/drm/i915/intel_sideband.c:40 vlv_sideband_rw+0x48/0x1ef() Modules linked in: CPU: 0 PID: 11136 Comm: kworker/u2:0 Tainted: G W 3.11.0-rc2+ #4 Call Trace: [<c2028564>] ? warn_slowpath_common+0x63/0x78 [<c227ad43>] ? vlv_sideband_rw+0x48/0x1ef [<c20285dd>] ? warn_slowpath_null+0xf/0x13 [<c227ad43>] ? vlv_sideband_rw+0x48/0x1ef [<c227b060>] ? vlv_dpio_write+0x1c/0x21 [<c2262b3b>] ? intel_dp_set_signal_levels+0x24a/0x385 [<c2264909>] ? intel_dp_complete_link_train+0x25/0x1d1 [<c2264c55>] ? intel_dp_check_link_status+0xf7/0x106 [<c2238ced>] ? i915_hotplug_work_func+0x17b/0x221 [<c203a204>] ? process_one_work+0x12e/0x210 [<c203a5e4>] ? worker_thread+0x116/0x1ad [<c203a4ce>] ? rescuer_thread+0x1cb/0x1cb [<c203d8f5>] ? kthread+0x67/0x6c [<c2457ebb>] ? ret_from_kernel_thread+0x1b/0x30 [<c203d88e>] ? init_completion+0x18/0x18 v2: Retire the locking in vlv_crtc_enable() and do it close to the meat. Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk> Reviewed-by: NJani Nikula <jani.nikula@intel.com> [danvet: Squash in a s/mutex_lock/mutex_unlock/ fixup spotted by the 0 day kernel build/coccinelle and reported by Dan Carpenter.] Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
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