[PATCH 06/18] drm/amd/display: intermittent underflow observed when PIP is toggled in Full screen

[Rodrigo Siqueira]

From: Tashfique Abdullah <tabdullah at amd.com>

[Why]
The MPCC may change and request data when the pipes are switching from 2
to 1 or 1 to 2. During the switch there is a possibility of underflow
and flicker/missing data.

[How]
During VBlank the MPCC won't request data. The trick is to delay and
wait on VBlank, ONLY when pipes are either turning on or off, right
before MPCC is reset for the pipes.

Signed-off-by: Tashfique Abdullah <Tashfique.Abdullah at amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr at amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
---
 drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c
index b9c20e30d99d..abcb06044e6e 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c
@@ -1695,6 +1695,15 @@ void dcn20_program_front_end_for_ctx(
 				&& context->res_ctx.pipe_ctx[i].stream)
 			hws->funcs.blank_pixel_data(dc, &context->res_ctx.pipe_ctx[i], true);
 
+	/* wait for outstanding pending changes before adding or removing planes */
+	for (i = 0; i < dc->res_pool->pipe_count; i++) {
+		if (context->res_ctx.pipe_ctx[i].update_flags.bits.disable ||
+				context->res_ctx.pipe_ctx[i].update_flags.bits.enable) {
+			dc->hwss.wait_for_pending_cleared(dc, context);
+			break;
+		}
+	}
+
 	/* Disconnect mpcc */
 	for (i = 0; i < dc->res_pool->pipe_count; i++)
 		if (context->res_ctx.pipe_ctx[i].update_flags.bits.disable
-- 
2.29.2