drm/msm/dpu: cast crtc_clk calculation to u64 in _dpu_core_perf_calc_clk()

There may be a potential integer overflow issue in
_dpu_core_perf_calc_clk(). crtc_clk is defined as u64, while
mode->vtotal, mode->hdisplay, and drm_mode_vrefresh(mode) are defined as
a smaller data type. The result of the calculation will be limited to
"int" in this case without correct casting. In screen with high
resolution and high refresh rate, integer overflow may happen.
So, we recommend adding an extra cast to prevent potential
integer overflow.

Fixes: c33b7c0 ("drm/msm/dpu: add support for clk and bw scaling for display")
Signed-off-by: Zichen Xie <[email protected]>
Reviewed-by: Abhinav Kumar <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/622206/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: Gax-c

drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c

@@ -80,7 +80,7 @@ static u64 _dpu_core_perf_calc_clk(const struct dpu_perf_cfg *perf_cfg,
 
 	mode = &state->adjusted_mode;
 
-	crtc_clk = mode->vtotal * mode->hdisplay * drm_mode_vrefresh(mode);
+	crtc_clk = (u64)mode->vtotal * mode->hdisplay * drm_mode_vrefresh(mode);
 
 	drm_atomic_crtc_for_each_plane(plane, crtc) {
 		pstate = to_dpu_plane_state(plane->state);