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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yongqiang Sun <yongqiang.sun@amd.com>,
        Tony Cheng <Tony.Cheng@amd.com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 044/168] drm/amd/display: Not doing optimize bandwidth if flip pending.
Date:   Tue, 28 Apr 2020 20:23:38 +0200
Message-Id: <20200428182237.448944669@linuxfoundation.org>
In-Reply-To: <20200428182231.704304409@linuxfoundation.org>
References: <20200428182231.704304409@linuxfoundation.org>
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From: Yongqiang Sun <yongqiang.sun@amd.com>

[ Upstream commit 9941b8129030c9202aaf39114477a0e58c0d6ffc ]

[Why]
In some scenario like 1366x768 VSR enabled connected with a 4K monitor
and playing 4K video in clone mode, underflow will be observed due to
decrease dppclk when previouse surface scan isn't finished

[How]
In this use case, surface flip is switching between 4K and 1366x768,
1366x768 needs smaller dppclk, and when decrease the clk and previous
surface scan is for 4K and scan isn't done, underflow will happen.  Not
doing optimize bandwidth in case of flip pending.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 71c574d1e8be2..2028dc017f7a0 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -1182,6 +1182,26 @@ bool dc_commit_state(struct dc *dc, struct dc_state *context)
 	return (result == DC_OK);
 }
 
+static bool is_flip_pending_in_pipes(struct dc *dc, struct dc_state *context)
+{
+	int i;
+	struct pipe_ctx *pipe;
+
+	for (i = 0; i < MAX_PIPES; i++) {
+		pipe = &context->res_ctx.pipe_ctx[i];
+
+		if (!pipe->plane_state)
+			continue;
+
+		/* Must set to false to start with, due to OR in update function */
+		pipe->plane_state->status.is_flip_pending = false;
+		dc->hwss.update_pending_status(pipe);
+		if (pipe->plane_state->status.is_flip_pending)
+			return true;
+	}
+	return false;
+}
+
 bool dc_post_update_surfaces_to_stream(struct dc *dc)
 {
 	int i;
@@ -1192,6 +1212,9 @@ bool dc_post_update_surfaces_to_stream(struct dc *dc)
 
 	post_surface_trace(dc);
 
+	if (is_flip_pending_in_pipes(dc, context))
+		return true;
+
 	for (i = 0; i < dc->res_pool->pipe_count; i++)
 		if (context->res_ctx.pipe_ctx[i].stream == NULL ||
 		    context->res_ctx.pipe_ctx[i].plane_state == NULL) {
-- 
2.20.1