On Tue, 2017-05-23 at 22:08 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Mario Kleiner <mario.kleiner.de@xxxxxxxxx> > > commit d63c277dc672e0c568481af043359420fa9d4736 upstream. > > Avoid big roundoff errors in scanline/hactive durations for > high pixel clocks, especially for >= 500 Mhz, and thereby > program more accurate display fifo watermarks. [...] > --- a/drivers/gpu/drm/amd/amdgpu/dce_v10_0.c > +++ b/drivers/gpu/drm/amd/amdgpu/dce_v10_0.c > @@ -1237,14 +1237,14 @@ static void dce_v10_0_program_watermarks > { > struct drm_display_mode *mode = &amdgpu_crtc->base.mode; > struct dce10_wm_params wm_low, wm_high; > - u32 pixel_period; > + u32 active_time; > u32 line_time = 0; > u32 latency_watermark_a = 0, latency_watermark_b = 0; > u32 tmp, wm_mask, lb_vblank_lead_lines = 0; > > if (amdgpu_crtc->base.enabled && num_heads && mode) { > - pixel_period = 1000000 / (u32)mode->clock; > - line_time = min((u32)mode->crtc_htotal * pixel_period, (u32)65535); > + active_time = 1000000UL * (u32)mode->crtc_hdisplay / (u32)mode->clock; > + line_time = min((u32) (1000000UL * (u32)mode->crtc_htotal / (u32)mode->clock), (u32)65535); [...] Won't these multiplications overflow if a >4K display is attached to a 32-bit machine? Ben. -- Ben Hutchings Software Developer, Codethink Ltd.