drm/amd/display: Improve x86 and dmub ips handshake

[Why]
There is a race condition between x86 and dmcub fw when attempting to exit
IPS2. Scenarios including exiting IPS2 before IPS2 has been entered. This
can cause unexpected hang when DMCUB attempt to exit while PMFW still
tries to enter IPS2.

[How]
A new design has been introduced to remove race conditions and improve the
handshake between x86 and DMCUB. An AON scratch register is borrowed from
PMFW to determine whether DMCUB has committed to IPS entry or not.

In the case when dmcub has committed IPS entry, x86 must poll until an exit
event occurred either from DMCUB(IPS1) or PMFW(IPS2). x86 will wait
upperbound of evaluation and IPS entry time to ensure IPS2 exit event has
been sent to PMFW.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Duncan Ma <duncan.ma@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index c0081d756694..c15b4d5c4e6c 100644
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -965,6 +965,8 @@ struct dc_debug_options {
 	bool replay_skip_crtc_disabled;
 	bool ignore_pg;/*do nothing, let pmfw control it*/
 	bool psp_disabled_wa;
+	unsigned int ips2_eval_delay_us;
+	unsigned int ips2_entry_delay_us;
 };
 
 struct gpu_info_soc_bounding_box_v1_0;