[PATCH v2] drm/msm/dpu: change _dpu_plane_calc_bw() to use u64 to avoid overflow

[Abhinav Kumar]

_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")
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/32
Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
---
 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 c2aaaded07ed..98c1b22e9bca 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
@@ -119,6 +119,7 @@ static u64 _dpu_plane_calc_bw(const struct dpu_mdss_cfg *catalog,
 	struct dpu_sw_pipe_cfg *pipe_cfg)
 {
 	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;
@@ -136,13 +137,12 @@ static u64 _dpu_plane_calc_bw(const struct dpu_mdss_cfg *catalog,
 	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;
 
 	if ((vbp+vpw) > hw_latency_lines)
 		do_div(plane_prefill_bw, (vbp+vpw));
-- 
2.40.1