linux-kernel - [PATCH AUTOSEL 6.4 10/31] drm/amd/display: Add stream overhead in BW calculations for 128b/132b

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Message-Id: <20230908193201.3462957-10-sashal@kernel.org>
Date:   Fri,  8 Sep 2023 15:31:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     George Shen <george.shen@....com>,
        Wenjing Liu <wenjing.liu@....com>,
        Alan Liu <haoping.liu@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, harry.wentland@....com,
        sunpeng.li@....com, Rodrigo.Siqueira@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, aric.cyr@....com, qingqing.zhuo@....com,
        jun.lei@....com, alvin.lee2@....com, Mike.Hsieh@....com,
        nasir.osman@....com, hamza.mahfooz@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.4 10/31] drm/amd/display: Add stream overhead in BW calculations for 128b/132b

From: George Shen <george.shen@....com>

[ Upstream commit 974764180838516f80a13257da67a1ec6afb87d4 ]

[Why]
Current BW calculations do not account for the additional padding added
for uncompressed pixel-to-symbol packing.

This results in X.Y being too low for 128b/132b SST streams in certain
scenarios. If X.Y is too low, end user can observe image corruption.

[How]
Add function to calculate stream overhead to timing BW calculation for
128b/132b SST cases.

Reviewed-by: Wenjing Liu <wenjing.liu@....com>
Acked-by: Alan Liu <haoping.liu@....com>
Signed-off-by: George Shen <george.shen@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/dc.h         |  2 +
 drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c | 42 +++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index 9279990e43694..508fd6ab58e80 100644
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -1375,6 +1375,8 @@ struct dc_plane_state *dc_get_surface_for_mpcc(struct dc *dc,
 
 uint32_t dc_get_opp_for_plane(struct dc *dc, struct dc_plane_state *plane);
 
+void dc_set_disable_128b_132b_stream_overhead(bool disable);
+
 /* The function returns minimum bandwidth required to drive a given timing
  * return - minimum required timing bandwidth in kbps.
  */
diff --git a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
index 2bdc47615543c..9a0c9f9353b41 100644
--- a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
+++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
@@ -40,6 +40,8 @@ static bool dsc_policy_enable_dsc_when_not_needed;
 
 static bool dsc_policy_disable_dsc_stream_overhead;
 
+static bool disable_128b_132b_stream_overhead;
+
 #ifndef MAX
 #define MAX(X, Y) ((X) > (Y) ? (X) : (Y))
 #endif
@@ -47,6 +49,41 @@ static bool dsc_policy_disable_dsc_stream_overhead;
 #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
 #endif
 
+/* Need to account for padding due to pixel-to-symbol packing
+ * for uncompressed 128b/132b streams.
+ */
+static uint32_t apply_128b_132b_stream_overhead(
+	const struct dc_crtc_timing *timing, const uint32_t kbps)
+{
+	uint32_t total_kbps = kbps;
+
+	if (disable_128b_132b_stream_overhead)
+		return kbps;
+
+	if (!timing->flags.DSC) {
+		struct fixed31_32 bpp;
+		struct fixed31_32 overhead_factor;
+
+		bpp = dc_fixpt_from_int(kbps);
+		bpp = dc_fixpt_div_int(bpp, timing->pix_clk_100hz / 10);
+
+		/* Symbols_per_HActive = HActive * bpp / (4 lanes * 32-bit symbol size)
+		 * Overhead_factor = ceil(Symbols_per_HActive) / Symbols_per_HActive
+		 */
+		overhead_factor = dc_fixpt_from_int(timing->h_addressable);
+		overhead_factor = dc_fixpt_mul(overhead_factor, bpp);
+		overhead_factor = dc_fixpt_div_int(overhead_factor, 128);
+		overhead_factor = dc_fixpt_div(
+			dc_fixpt_from_int(dc_fixpt_ceil(overhead_factor)),
+			overhead_factor);
+
+		total_kbps = dc_fixpt_ceil(
+			dc_fixpt_mul_int(overhead_factor, total_kbps));
+	}
+
+	return total_kbps;
+}
+
 uint32_t dc_bandwidth_in_kbps_from_timing(
 	const struct dc_crtc_timing *timing)
 {
@@ -1160,6 +1197,11 @@ void dc_dsc_policy_set_disable_dsc_stream_overhead(bool disable)
 	dsc_policy_disable_dsc_stream_overhead = disable;
 }
 
+void dc_set_disable_128b_132b_stream_overhead(bool disable)
+{
+	disable_128b_132b_stream_overhead = disable;
+}
+
 void dc_dsc_get_default_config_option(const struct dc *dc, struct dc_dsc_config_options *options)
 {
 	options->dsc_min_slice_height_override = dc->debug.dsc_min_slice_height_override;
-- 
2.40.1