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This adds a mutex lock for both DPM/PP around the changes in
power gating state so that userspace can poll registers without
a race condition on power state.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>