On 2024-03-14 09:31, Melissa Wen wrote: > On 03/14, Melissa Wen wrote: >> On 03/13, Arthur Grillo wrote: >>> >>> >>> On 12/03/24 15:27, Melissa Wen wrote: >>>> On 03/06, Arthur Grillo wrote: >>>>> As well noted by Pekka[1], the rounding of drm_fixp2int_round is wrong. >>>>> To round a number, you need to add 0.5 to the number and floor that, >>>>> drm_fixp2int_round() is adding 0.0000076. Make it add 0.5. >>>>> >>>>> [1]: https://lore.kernel.org/all/20240301135327.22efe0dd.pekka.paalanen@xxxxxxxxxxxxx/ >>>>> >>>> Hi Arthur, >>>> >>>> thanks for addressing this issue. >>>> >>>> Please, add a fix tag to the commit that you are fixing, so we can >>>> easily backport. Might be this commit: >>>> https://cgit.freedesktop.org/drm/drm-misc/commit/drivers/gpu/drm/vkms?id=ab87f558dcfb2562c3497e89600dec798a446665 >>>>> Suggested-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx> >>>>> Signed-off-by: Arthur Grillo <arthurgrillo@xxxxxxxxxx> >>>>> --- >>>>> include/drm/drm_fixed.h | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h >>>>> index 0c9f917a4d4b..de3a79909ac9 100644 >>>>> --- a/include/drm/drm_fixed.h >>>>> +++ b/include/drm/drm_fixed.h >>>>> @@ -90,7 +90,7 @@ static inline int drm_fixp2int(s64 a) >>>>> >>>>> static inline int drm_fixp2int_round(s64 a) >>>>> { >>>>> - return drm_fixp2int(a + (1 << (DRM_FIXED_POINT_HALF - 1))); >>>> Also, this is the only usage of DRM_FIXED_POINT_HALF. Can you also >>>> remove it as it won't be used anymore? >>>> >>>>> + return drm_fixp2int(a + DRM_FIXED_ONE / 2); >>>> Would this division be equivalent to just shifting 1ULL by 31 instead of >>>> 32 as done in DRM_FIXED_ONE? >>> >>> Yes, but I think the division makes it easier to understand what is >>> going on. >> >> Right. I was thinking about slightly better performance, but I don't >> have any data. We can go with this since you consider more readable, >> anyway. > > Just checked that Harry proposed in another patch[1] this: > `#define DRM_FIXED_HALF 0x80000000ll` for the 0.5 const > > Doesn't it sounds better? > I tend to agree with Arthur and Pekka. DRM_FIXED_ONE / 2 makes it really clear what's happening here. And I'd imagine compilers would optimize it out anyways. Obviously not opposed to a define but if it's only used in one place I don't think it matters much. Harry > [1] https://lore.kernel.org/dri-devel/20240226211100.100108-4-harry.wentland@xxxxxxx/ >> >> Can you send another version addressing the other comments? Then I can >> cherry-pick and already apply the fix. >> >> Thanks, >> >> Melissa >> >>> >>> Best Regards, >>> ~Arthur Grillo >>> >>>> >>>> Melissa >>>> >>>>> } >>>>> >>>>> static inline int drm_fixp2int_ceil(s64 a) >>>>> >>>>> -- >>>>> 2.43.0 >>>>>
