drm/amd/display: Add shared firmware state for DMUB IPS handshake
[Why] Read modify write hazards can occur when using a single shared scratch register between driver and firmware leading to driver accessing DCN in IPS2 and a system hang. [How] Add infrastructure for using REGION6 as a shared firmware state between driver and firmware. This region is uncachable. Replace the existing get/set idle calls with reads/writes to the (volatile) shared firmware state blocks that a separated by at least a cache line between firmware and driver. Remove the workarounds that required rewriting/checking read modify write hazards. Reviewed-by: Charlene Liu <charlene.liu@amd.com> Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com> Tested-by: Daniel Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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