>-----Original Message----- >From: Ville Syrjälä [mailto:ville.syrjala@xxxxxxxxxxxxxxx] >Sent: Friday, December 22, 2017 9:43 PM >To: Shankar, Uma <uma.shankar@xxxxxxxxx> >Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Lin, Johnson <johnson.lin@xxxxxxxxx>; >Syrjala, Ville <ville.syrjala@xxxxxxxxx>; Lankhorst, Maarten ><maarten.lankhorst@xxxxxxxxx> >Subject: Re: [PATCH] drm/i915: Fix Limited Range Color Handling > >On Fri, Dec 22, 2017 at 05:54:31PM +0200, Ville Syrjälä wrote: >> On Fri, Dec 22, 2017 at 08:34:47PM +0530, Uma Shankar wrote: >> > From: Johnson Lin <johnson.lin@xxxxxxxxx> >> > >> > Some panels support limited range output (16-235) compared to full >> > range RGB values (0-255). Also userspace can control the RGB range >> > using "Broadcast RGB" property. Currently the code to handle full >> > range to limited range is broken. This patch fixes the same by >> > properly scaling down all the full range co-efficients with limited >> > range scaling factor. >> > >> > Signed-off-by: Johnson Lin <johnson.lin@xxxxxxxxx> >> > Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx> >> > --- >> > drivers/gpu/drm/i915/intel_color.c | 16 ++++++++++++---- >> > 1 file changed, 12 insertions(+), 4 deletions(-) >> > >> > diff --git a/drivers/gpu/drm/i915/intel_color.c >> > b/drivers/gpu/drm/i915/intel_color.c >> > index aa66e95..777ce26 100644 >> > --- a/drivers/gpu/drm/i915/intel_color.c >> > +++ b/drivers/gpu/drm/i915/intel_color.c >> > @@ -94,16 +94,24 @@ static void ctm_mult_by_limited(uint64_t *result, >int64_t *input) >> > for (i = 0; i < 9; i++) >> > result[i] = 0; >> >> This can go. >> >> > >> > - for (i = 0; i < 3; i++) { >> > - int64_t user_coeff = input[i * 3 + i]; >> > + for (i = 0; i < 9; i++) { >> > + int64_t user_coeff = input[i]; >> >> That's not a two's complement number so should probably be u64. >> >> > uint64_t limited_coeff = CTM_COEFF_LIMITED_RANGE >> 2; >> > uint64_t abs_coeff = clamp_val(CTM_COEFF_ABS(user_coeff), >> > 0, >> > CTM_COEFF_4_0 - 1) >> 2; >> >> Seems to me that we should be able to drop the >>2 from the >> limited_coeff since it's always < 1.0, make both of these u32 and then >> use >> 'mul_u32_u32() >> 30' to get the answer. >> >> > >> > - result[i * 3 + i] = (limited_coeff * abs_coeff) >> 27; >> > + /* >> > + * By scaling every co-efficient with limited range (235-16) >> > + * vs full range (0-255) the final o/p will be scaled down to >> > + * fit in the limited range supported by the panel. >> > + * Need to shift the multiplication result by 28 as the floating >> > + * count expected is of 32bits, multiplication here is done in >> > + * U2.30 so result need to be right shifted by 60-32 = 28 >> > + */ >> > + result[i] = (limited_coeff * abs_coeff) >> 28; >> > if (CTM_COEFF_NEGATIVE(user_coeff)) >> >> And this can be replaced with just >> >> result[i] |= user_coeff & CTM_COEFF_SIGN; >> >> to eliminate the silly branch. > >I wonder if we could also get some igts for this limited range stuff. >Maybe something like: >1. grab crc from black/white screen with limited range 2. grab cdc from almost >black/white screen with full range 3. compare the two > >Repeat with an identity csc matrix set. > >Not sure if we can get the crcs to match in these two cases though. >Hard to say without trying it out. > Hi Ville, We will try this approach and update. Ideally crc's should match, will confirm the behavior on hardware. Thanks & Regards, Uma Shankar >> >> >> > - result[i * 3 + i] |= CTM_COEFF_SIGN; >> > + result[i] |= CTM_COEFF_SIGN; >> > } >> > } >> > >> > -- >> > 1.7.9.5 >> > >> > _______________________________________________ >> > Intel-gfx mailing list >> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx >> >> -- >> Ville Syrjälä >> Intel OTC > >-- >Ville Syrjälä >Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
