On Thu, May 03, 2018 at 01:22:13PM +0200, Maarten Lankhorst wrote: > When calculating limits we want to be as pessimistic as possible, > so we have to explicitly say whether we want to round up or down > to accurately calculate whether we are below min_scale or above > max_scale. > > Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_rect.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c > index a3783ecea297..4735526297aa 100644 > --- a/drivers/gpu/drm/drm_rect.c > +++ b/drivers/gpu/drm/drm_rect.c > @@ -106,7 +106,10 @@ static int drm_calc_scale(int src, int dst) > if (dst == 0) > return 0; > > - scale = src / dst; > + if (src > (dst << 16)) > + return DIV_ROUND_UP(src, dst); > + else > + scale = src / dst; > > return scale; > } > @@ -121,6 +124,9 @@ static int drm_calc_scale(int src, int dst) > * Calculate the horizontal scaling factor as > * (@src width) / (@dst width). > * > + * If the scale is below 1 << 16, round down, if above up. This will The "if above up" part doesn't read all that well to me. Maybe write it out fully "If the scale is above 1 << 16, round up"? Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > + * calculate the scale with the most pessimistic limit calculation. > + * > * RETURNS: > * The horizontal scaling factor, or errno of out of limits. > */ > @@ -152,6 +158,9 @@ EXPORT_SYMBOL(drm_rect_calc_hscale); > * Calculate the vertical scaling factor as > * (@src height) / (@dst height). > * > + * If the scale is below 1 << 16, round down, if above up. This will > + * calculate the scale with the most pessimistic limit calculation. > + * > * RETURNS: > * The vertical scaling factor, or errno of out of limits. > */ > @@ -189,6 +198,9 @@ EXPORT_SYMBOL(drm_rect_calc_vscale); > * If the calculated scaling factor is above @max_vscale, > * decrease the height of rectangle @src to compensate. > * > + * If the scale is below 1 << 16, round down, if above up. This will > + * calculate the scale with the most pessimistic limit calculation. > + * > * RETURNS: > * The horizontal scaling factor. > */ > @@ -239,6 +251,9 @@ EXPORT_SYMBOL(drm_rect_calc_hscale_relaxed); > * If the calculated scaling factor is above @max_vscale, > * decrease the height of rectangle @src to compensate. > * > + * If the scale is below 1 << 16, round down, if above up. This will > + * calculate the scale with the most pessimistic limit calculation. > + * > * RETURNS: > * The vertical scaling factor. > */ > -- > 2.17.0 -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
