[PATCH 6.1 037/131] drm/msm/dpu: change _dpu_plane_calc_bw() to use u64 to avoid overflow

Greg Kroah-Hartman
2023-10-16T08:56:32Z

From: Abhinav Kumar <quic_abhinavk@quicinc.com>

[ 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@linaro.org>
Reported-by: Nia Espera <nespera@igalia.com>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/32
Tested-by: Nia Espera <nespera@igalia.com>
Patchwork: https://patchwork.freedesktop.org/patch/556288/
Link: https://lore.kernel.org/r/20230908012616.20654-1-quic_abhinavk@quicinc.com
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3fbda2a1f77fc..62d48c0f905e4 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
@@ -142,6 +142,7 @@ 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;
@@ -164,13 +165,12 @@ 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;

if ((vbp+vpw) > hw_latency_lines)
do_div(plane_prefill_bw, (vbp+vpw));
--
2.40.1