[PATCH 5.10 012/202] drm/msm/dpu: change _dpu_plane_calc_bw() to use u64 to avoid overflow

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>

[ Upstream commit 95e681ca3b65e4ce3d2537b47672d787b7d30375 ]

_dpu_plane_calc_bw() uses integer variables to calculate the bandwidth
used during plane bandwidth calculations. However for high resolution
displays this overflows easily and leads to below errors

[dpu error]crtc83 failed performance check -7

Promote the intermediate variables to u64 to avoid overflow.

changes in v2:
	- change to u64 where actually needed in the math

Fixes: c33b7c0389e1 ("drm/msm/dpu: add support for clk and bw scaling for display")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Reported-by: Nia Espera <nespera@xxxxxxxxxx>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/32
Tested-by: Nia Espera <nespera@xxxxxxxxxx>
Patchwork: https://patchwork.freedesktop.org/patch/556288/
Link: https://lore.kernel.org/r/20230908012616.20654-1-quic_abhinavk@xxxxxxxxxxx
Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
index 7ea90d25a3b69..8aa9f2335f57a 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
@@ -147,6 +147,7 @@ static void _dpu_plane_calc_bw(struct drm_plane *plane,
 	const struct dpu_format *fmt = NULL;
 	struct dpu_kms *dpu_kms = _dpu_plane_get_kms(plane);
 	int src_width, src_height, dst_height, fps;
+	u64 plane_pixel_rate, plane_bit_rate;
 	u64 plane_prefill_bw;
 	u64 plane_bw;
 	u32 hw_latency_lines;
@@ -168,13 +169,12 @@ static void _dpu_plane_calc_bw(struct drm_plane *plane,
 	scale_factor = src_height > dst_height ?
 		mult_frac(src_height, 1, dst_height) : 1;
 
-	plane_bw =
-		src_width * mode->vtotal * fps * fmt->bpp *
-		scale_factor;
+	plane_pixel_rate = src_width * mode->vtotal * fps;
+	plane_bit_rate = plane_pixel_rate * fmt->bpp;
 
-	plane_prefill_bw =
-		src_width * hw_latency_lines * fps * fmt->bpp *
-		scale_factor * mode->vtotal;
+	plane_bw = plane_bit_rate * scale_factor;
+
+	plane_prefill_bw = plane_bw * hw_latency_lines;
 
 	do_div(plane_prefill_bw, (vbp+vpw));
 
-- 
2.40.1






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