drm/amd/display: Disable idle reallow as part of command/gpint execution

[Why]
Workaroud for a race condition where DMCUB is in the process of
committing to IPS1 during the handshake causing us to miss the
transition into IPS2 and touch the INBOX1 RPTR causing a HW hang.

[How]
Disable the reallow to ensure that we have enough of a gap between entry
and exit and we're not seeing back-to-back wake_and_executes.
Reviewed-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc.h

@@ -987,6 +987,7 @@ struct dc_debug_options {
 	bool psp_disabled_wa;
 	unsigned int ips2_eval_delay_us;
 	unsigned int ips2_entry_delay_us;
+	bool disable_dmub_reallow_idle;
 	bool disable_timeout;
 	bool disable_extblankadj;
 	unsigned int static_screen_wait_frames;

drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c

@@ -1374,7 +1374,7 @@ bool dc_wake_and_execute_dmub_cmd_list(const struct dc_context *ctx, unsigned in
 	else
 		result = dm_execute_dmub_cmd(ctx, cmd, wait_type);
 
-	if (result && reallow_idle)
+	if (result && reallow_idle && !ctx->dc->debug.disable_dmub_reallow_idle)
 		dc_dmub_srv_apply_idle_power_optimizations(ctx->dc, true);
 
 	return result;
@@ -1423,7 +1423,7 @@ bool dc_wake_and_execute_gpint(const struct dc_context *ctx, enum dmub_gpint_com
 
 	result = dc_dmub_execute_gpint(ctx, command_code, param, response, wait_type);
 
-	if (result && reallow_idle)
+	if (result && reallow_idle && !ctx->dc->debug.disable_dmub_reallow_idle)
 		dc_dmub_srv_apply_idle_power_optimizations(ctx->dc, true);
 
 	return result;

drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c

@@ -783,6 +783,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.psp_disabled_wa = true,
 	.ips2_eval_delay_us = 1650,
 	.ips2_entry_delay_us = 800,
+	.disable_dmub_reallow_idle = true,
 	.static_screen_wait_frames = 2,
 };