[cc'ing the authors]
On Sat, Apr 11, 2015 at 07:40:34PM -0300, Ismael Luceno wrote:
> A bisect showed that commit 32b7eeec4d1e861230b09d437e95d76c86ff4a68
> introduced the issue.
>
> The issue starts as soon as X takes control of the screen, even if just
> a plain X doing nothing, so based on the code touched by the commit I
> thought it had to be related to the so called "hardware cursor". I
> confirmed it when hiding the cursor made the flickering go away.
>
> The aforementioned commit removed some suspicious code, and the
> Programmer's Reference Manual confirmed my suspicion:
>
> "Incorrectly programmed watermark values can result in screen corruption.
>
> The watermarks should be calculated and programmed when any of the
> watermark calculation inputs change. This includes planes enabling or
> disabling, plane source format or size changing, etc."
>
> So I'm re-adding the few lines that update the watermarks after a cursor
> size change.
>
> Signed-off-by: Ismael Luceno <ism...@iodev.co.uk>
> ---
> drivers/gpu/drm/i915/intel_display.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c
> index f75173c..e23f062 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12258,6 +12258,7 @@ intel_commit_cursor_plane(struct drm_plane *plane,
> struct intel_crtc *intel_crtc;
> struct intel_plane *intel_plane = to_intel_plane(plane);
> struct drm_i915_gem_object *obj = intel_fb_obj(state->base.fb);
> + unsigned old_width;
> uint32_t addr;
>
> crtc = crtc ? crtc : plane->crtc;
> @@ -12282,11 +12283,15 @@ intel_commit_cursor_plane(struct drm_plane *plane,
> intel_crtc->cursor_addr = addr;
> intel_crtc->cursor_bo = obj;
> update:
> + old_width = intel_crtc->cursor_width;
> intel_crtc->cursor_width = state->base.crtc_w;
> intel_crtc->cursor_height = state->base.crtc_h;
>
> - if (intel_crtc->active)
> + if (intel_crtc->active) {
> + if (old_width != intel_crtc->cursor_width)
> + intel_update_watermarks(crtc);
> intel_crtc_update_cursor(crtc, state->visible);
> + }
> }
>
> static struct drm_plane *intel_cursor_plane_create(struct drm_device *dev,
> --
> 2.3.4
--
Chris Wilson, Intel Open Source Technology Centre
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