[PATCH 11/13] drm/amd/display: Force p-state disallow if leaving no plane config

[Aurabindo Pillai <aurabindo.pillai@xxxxxxx>]

From: Alvin Lee <alvin.lee2@xxxxxxx>

[Description]
- When we're in a no plane config, DCN is always asserting
  P-State allow
- This creates a scenario where the P-State blackout can start
  just as VUPDATE takes place and transitions the DCN config to
  a one where one or more HUBP's are active which can result in
  underflow
- To fix this issue, force p-state disallow and unforce after
  the transition from no planes case -> one or more planes active

Reviewed-by: Samson Tam <samson.tam@xxxxxxx>
Acked-by: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Signed-off-by: Alvin Lee <alvin.lee2@xxxxxxx>
---
 .../amd/display/dc/hwss/dcn20/dcn20_hwseq.c   | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
index 608221b0dd5d..c3c83178eb1e 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
@@ -1877,6 +1877,8 @@ void dcn20_program_front_end_for_ctx(
 	int i;
 	struct dce_hwseq *hws = dc->hwseq;
 	DC_LOGGER_INIT(dc->ctx->logger);
+	unsigned int prev_hubp_count = 0;
+	unsigned int hubp_count = 0;
 
 	if (resource_is_pipe_topology_changed(dc->current_state, context))
 		resource_log_pipe_topology_update(dc, context);
@@ -1894,6 +1896,20 @@ void dcn20_program_front_end_for_ctx(
 		}
 	}
 
+	for (i = 0; i < dc->res_pool->pipe_count; i++) {
+		if (dc->current_state->res_ctx.pipe_ctx[i].plane_state)
+			prev_hubp_count++;
+		if (context->res_ctx.pipe_ctx[i].plane_state)
+			hubp_count++;
+	}
+
+	if (prev_hubp_count == 0 && hubp_count > 0) {
+		if (dc->res_pool->hubbub->funcs->force_pstate_change_control)
+			dc->res_pool->hubbub->funcs->force_pstate_change_control(
+					dc->res_pool->hubbub, true, false);
+		udelay(500);
+	}
+
 	/* Set pipe update flags and lock pipes */
 	for (i = 0; i < dc->res_pool->pipe_count; i++)
 		dcn20_detect_pipe_changes(&dc->current_state->res_ctx.pipe_ctx[i],
@@ -2039,6 +2055,10 @@ void dcn20_post_unlock_program_front_end(
 		}
 	}
 
+	if (dc->res_pool->hubbub->funcs->force_pstate_change_control)
+		dc->res_pool->hubbub->funcs->force_pstate_change_control(
+				dc->res_pool->hubbub, false, false);
+
 	for (i = 0; i < dc->res_pool->pipe_count; i++) {
 		struct pipe_ctx *pipe = &context->res_ctx.pipe_ctx[i];
 
-- 
2.39.2