On Thu, May 03, 2018 at 01:22:14PM +0200, Maarten Lankhorst wrote:
> Instead of relying on a scale which may increase rounding errors,
> clip src by doing: src * (dst - clip) / dst and rounding the result
> away from 1, so the new coordinates get closer to 1. We won't need
> to fix up with a magic macro afterwards, because our scaling factor
> will never go to the other side of 1.
>
> Changes since v1:
> - Adjust dst immediately, else drm_rect_width/height on dst gives bogus
> results.
> Change since v2:
> - Get rid of macros and use 64-bits math.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 2 +-
> drivers/gpu/drm/drm_rect.c | 45 ++++++++++++++++++++---------
> drivers/gpu/drm/i915/intel_sprite.c | 2 +-
> include/drm/drm_rect.h | 3 +-
> 4 files changed, 35 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 9cb2209f6fc8..130da5195f3b 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -766,7 +766,7 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
> if (crtc_state->enable)
> drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>
> - plane_state->visible = drm_rect_clip_scaled(src, dst, &clip, hscale, vscale);
> + plane_state->visible = drm_rect_clip_scaled(src, dst, &clip);
>
> drm_rect_rotate_inv(src, fb->width << 16, fb->height << 16, rotation);
>
> diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c
> index 4735526297aa..f477063f18ea 100644
> --- a/drivers/gpu/drm/drm_rect.c
> +++ b/drivers/gpu/drm/drm_rect.c
> @@ -50,13 +50,21 @@ bool drm_rect_intersect(struct drm_rect *r1, const struct drm_rect *r2)
> }
> EXPORT_SYMBOL(drm_rect_intersect);
>
> +static u32 clip_scaled(u32 src, u32 dst, u32 clip)
> +{
> + u64 newsrc = mul_u32_u32(src, dst - clip);
'newsrc' feels slightly misleading. It would be a decent name for
the final return value of the function, but for this intermediate
value 'tmp' or something equally non specific might be better.
> +
> + if (src < (dst << 16))
> + return DIV_ROUND_UP_ULL(newsrc, dst);
> + else
> + return DIV_ROUND_DOWN_ULL(newsrc, dst);
I think we could use a comment here to explain the choice of
rounding direction. Eg.
/*
* Round toward 1.0 when clipping so that we don't accidentally
* change upscaling to downscaling or vice versa.
*/
?
> +}
> +
> /**
> * drm_rect_clip_scaled - perform a scaled clip operation
> * @src: source window rectangle
> * @dst: destination window rectangle
> * @clip: clip rectangle
> - * @hscale: horizontal scaling factor
> - * @vscale: vertical scaling factor
> *
> * Clip rectangle @dst by rectangle @clip. Clip rectangle @src by the
> * same amounts multiplied by @hscale and @vscale.
> @@ -66,33 +74,44 @@ EXPORT_SYMBOL(drm_rect_intersect);
> * %false otherwise
> */
> bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
> - const struct drm_rect *clip,
> - int hscale, int vscale)
> + const struct drm_rect *clip)
> {
> int diff;
>
> diff = clip->x1 - dst->x1;
> if (diff > 0) {
> - int64_t tmp = src->x1 + (int64_t) diff * hscale;
> - src->x1 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
> + u32 new_src_w = clip_scaled(drm_rect_width(src),
> + drm_rect_width(dst), diff);
Could have precomputed the src/dst width/height upfront maybe.
Oh, I guess you can't since your clip_scaled() uses the dst width/height
for more than the scaling factor. If it just computed diff*src/dst
like the original code does then precomputing would work just fine.
Your way feels a bit more complicated to me, but looks like it should
work.
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> +
> + src->x1 = clamp_t(int64_t, src->x2 - new_src_w, INT_MIN, INT_MAX);
> + dst->x1 = clip->x1;
> }
> diff = clip->y1 - dst->y1;
> if (diff > 0) {
> - int64_t tmp = src->y1 + (int64_t) diff * vscale;
> - src->y1 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
> + u32 new_src_h = clip_scaled(drm_rect_height(src),
> + drm_rect_height(dst), diff);
> +
> + src->y1 = clamp_t(int64_t, src->y2 - new_src_h, INT_MIN, INT_MAX);
> + dst->y1 = clip->y1;
> }
> diff = dst->x2 - clip->x2;
> if (diff > 0) {
> - int64_t tmp = src->x2 - (int64_t) diff * hscale;
> - src->x2 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
> + u32 new_src_w = clip_scaled(drm_rect_width(src),
> + drm_rect_width(dst), diff);
> +
> + src->x2 = clamp_t(int64_t, src->x1 + new_src_w, INT_MIN, INT_MAX);
> + dst->x2 = clip->x2;
> }
> diff = dst->y2 - clip->y2;
> if (diff > 0) {
> - int64_t tmp = src->y2 - (int64_t) diff * vscale;
> - src->y2 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
> + u32 new_src_h = clip_scaled(drm_rect_height(src),
> + drm_rect_height(dst), diff);
> +
> + src->y2 = clamp_t(int64_t, src->y1 + new_src_h, INT_MIN, INT_MAX);
> + dst->y2 = clip->y2;
> }
>
> - return drm_rect_intersect(dst, clip);
> + return drm_rect_visible(dst);
> }
> EXPORT_SYMBOL(drm_rect_clip_scaled);
>
> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> index aa1dfaa692b9..44d7aca222b0 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -1008,7 +1008,7 @@ intel_check_sprite_plane(struct intel_plane *plane,
> drm_mode_get_hv_timing(&crtc_state->base.mode,
> &clip.x2, &clip.y2);
>
> - state->base.visible = drm_rect_clip_scaled(src, dst, &clip, hscale, vscale);
> + state->base.visible = drm_rect_clip_scaled(src, dst, &clip);
>
> crtc_x = dst->x1;
> crtc_y = dst->y1;
> diff --git a/include/drm/drm_rect.h b/include/drm/drm_rect.h
> index 44bc122b9ee0..6c54544a4be7 100644
> --- a/include/drm/drm_rect.h
> +++ b/include/drm/drm_rect.h
> @@ -175,8 +175,7 @@ static inline bool drm_rect_equals(const struct drm_rect *r1,
>
> bool drm_rect_intersect(struct drm_rect *r, const struct drm_rect *clip);
> bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
> - const struct drm_rect *clip,
> - int hscale, int vscale);
> + const struct drm_rect *clip);
> int drm_rect_calc_hscale(const struct drm_rect *src,
> const struct drm_rect *dst,
> int min_hscale, int max_hscale);
> --
> 2.17.0
--
Ville Syrjälä
Intel
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