On Mon, May 06, 2019 at 04:09:33PM +0530, Sharma, Shashank wrote:
> Regards
>
> Shashank
>
> On 5/3/2019 9:20 PM, Ville Syrjälä wrote:
> > On Tue, Apr 30, 2019 at 08:51:08PM +0530, Shashank Sharma wrote:
> >> ICL introduces a new gamma correction mode in display engine, called
> >> multi-segmented-gamma mode. This mode allows users to program the
> >> darker region of the gamma curve with sueprfine precision. An
> >> example use case for this is HDR curves (like PQ ST-2084).
> >>
> >> If we plot a gamma correction curve from value range between 0.0 to 1.0,
> >> ICL's multi-segment has 3 different sections:
> >> - superfine segment: 9 values, ranges between 0 - 1/(128 * 256)
> >> - fine segment: 257 values, ranges between 0 - 1/(128)
> >> - corase segment: 257 values, ranges between 0 - 1
> >>
> >> This patch:
> >> - Changes gamma LUTs size for ICL/GEN11 to 262144 entries (8 * 128 * 256),
> >> so that userspace can program with highest precision supported.
> >> - Changes default gamma mode (non-legacy) to multi-segmented-gamma mode.
> >> - Adds functions to program/detect multi-segment gamma.
> >>
> >> V2: Addressed review comments from Ville
> >> - separate function for superfine and fine segments.
> >> - remove enum for segments.
> >> - reuse last entry of the LUT as gc_max value.
> >> - replace if() ....cond with switch...case in icl_load_luts.
> >> - add an entry variable, instead of 'word'
> >>
> >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> >> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> >>
> >> Suggested-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >> Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxxxx>
> >> Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx>
> >> ---
> >> drivers/gpu/drm/i915/i915_pci.c | 3 +-
> >> drivers/gpu/drm/i915/intel_color.c | 125 ++++++++++++++++++++++++++++-
> >> 2 files changed, 123 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> >> index ffa2ee70a03d..83698951760b 100644
> >> --- a/drivers/gpu/drm/i915/i915_pci.c
> >> +++ b/drivers/gpu/drm/i915/i915_pci.c
> >> @@ -749,7 +749,8 @@ static const struct intel_device_info intel_cannonlake_info = {
> >> GEN(11), \
> >> .ddb_size = 2048, \
> >> .has_logical_ring_elsq = 1, \
> >> - .color = { .degamma_lut_size = 33, .gamma_lut_size = 1024 }
> >> + .color = { .degamma_lut_size = 33, .gamma_lut_size = 262144 }
> > Ugh. Thats one big LUT. But looks correct.
> >
> >> +
> > Bogus newline.
> Got it.
> >>
> >> static const struct intel_device_info intel_icelake_11_info = {
> >> GEN11_FEATURES,
> >> diff --git a/drivers/gpu/drm/i915/intel_color.c b/drivers/gpu/drm/i915/intel_color.c
> >> index 6c341bea514c..49831e8d02fb 100644
> >> --- a/drivers/gpu/drm/i915/intel_color.c
> >> +++ b/drivers/gpu/drm/i915/intel_color.c
> >> @@ -41,6 +41,9 @@
> >> #define CTM_COEFF_ABS(coeff) ((coeff) & (CTM_COEFF_SIGN - 1))
> >>
> >> #define LEGACY_LUT_LENGTH 256
> >> +#define ICL_GAMMA_MULTISEG_LUT_LENGTH (256 * 128 * 8)
> >> +#define ICL_GAMMA_SUPERFINE_SEG_LENGTH 9
> >> +
> >> /*
> >> * Extract the CSC coefficient from a CTM coefficient (in U32.32 fixed point
> >> * format). This macro takes the coefficient we want transformed and the
> >> @@ -767,6 +770,113 @@ static void glk_load_luts(const struct intel_crtc_state *crtc_state)
> >> }
> >> }
> >>
> >> +/* ilk+ "12.4" interpolated format (high 10 bits) */
> >> +static u32 ilk_lut_12p4_ldw(const struct drm_color_lut *color)
> >> +{
> >> + return (color->red >> 6) << 20 | (color->green >> 6) << 10 |
> >> + (color->blue >> 6);
> >> +}
> >> +
> >> +/* ilk+ "12.4" interpolated format (low 6 bits) */
> >> +static u32 ilk_lut_12p4_udw(const struct drm_color_lut *color)
> >> +{
> >> + return (color->red & 0x3f) << 24 | (color->green & 0x3f) << 14 |
> >> + (color->blue & 0x3f);
> >> +}
> >> +
> >> +static void
> >> +icl_load_gcmax(const struct intel_crtc_state *crtc_state,
> >> + const struct drm_color_lut *entry)
> > Indentation looks off. Also s/entry/color/ to match the other similarish
> > funcs maybe?
> Sure.
> >> +{
> >> + struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
> >> + struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> >> + enum pipe pipe = crtc->pipe;
> >> +
> >> + /* Fixme: LUT entries are 16 bit only, so we can prog 0xFFFF max */
> >> + I915_WRITE(PREC_PAL_GC_MAX(pipe, 0), entry->red);
> >> + I915_WRITE(PREC_PAL_GC_MAX(pipe, 1), entry->green);
> >> + I915_WRITE(PREC_PAL_GC_MAX(pipe, 2), entry->blue);
> >> +}
> >> +
> >> +static void
> >> +icl_program_gamma_superfine_segment(const struct intel_crtc_state *crtc_state)
> >> +{
> >> + struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
> >> + struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> >> + const struct drm_property_blob *blob = crtc_state->base.gamma_lut;
> >> + const struct drm_color_lut *lut = blob->data;
> >> + enum pipe pipe = crtc->pipe;
> >> + u32 i;
> >> +
> >> + if (!lut || drm_color_lut_size(blob) < ICL_GAMMA_SUPERFINE_SEG_LENGTH)
> >> + return;
> > These checks aren't needed. Just dead code.
> Will remove this and similars.
> >> +
> >> + /*
> >> + * Every entry in the multi-segment LUT is corresponding to a superfine
> >> + * segment step which is 1/(8 * 128 * 256).
> >> + *
> >> + * Superfine segment has 9 entries, corresponding to values
> >> + * 0, 1/(8 * 128 * 256), 2/(8 * 128 * 256) .... 8/(8 * 128 * 256).
> >> + */
> >> + I915_WRITE(PREC_PAL_MULTI_SEG_INDEX(pipe), PAL_PREC_AUTO_INCREMENT);
> >> +
> >> + for (i = 0; i < 9; i++) {
> >> + const struct drm_color_lut *entry = &lut[i];
> >> +
> >> + I915_WRITE(PREC_PAL_MULTI_SEG_DATA(pipe),
> >> + ilk_lut_12p4_udw(entry));
> > ldw should come before udw.
> Got it.
> >> + I915_WRITE(PREC_PAL_MULTI_SEG_DATA(pipe),
> >> + ilk_lut_12p4_ldw(entry));
> >> + }
> >> +}
> >> +
> >> +static void
> >> +icl_program_gamma_multi_segment(const struct intel_crtc_state *crtc_state)
> >> +{
> >> + struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
> >> + struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> >> + const struct drm_property_blob *blob = crtc_state->base.gamma_lut;
> >> + const struct drm_color_lut *lut = blob->data;
> >> + const struct drm_color_lut *entry;
> > 'entry' declaration can be moved into the loops.
> Its being used in multiple loops,
IMO still better to move into the loops. We don't want to pass any
information between the loops.
> also being used for GCMax outside the
> loop.
Hmm. That might be an arguemnt for keeping it out. But the current
gcmax usage looks broken. You're programming the same value into
the last PAL_PREC index and GCMAX.
> >> + enum pipe pipe = crtc->pipe;
> >> + u32 i;
> >> +
> >> + if (!lut || (drm_color_lut_size(blob) < ICL_GAMMA_MULTISEG_LUT_LENGTH))
> >> + return;
> > More checks that aren't needed.
> Got it.
> >> +
> >> + /*
> >> + * Every entry in the multi-segment LUT is corresponding to a superfine
> >> + * segment step which is 1/(8*128*256).
> >> + *
> >> + * Fine segment's step is 1/(128 * 256) ie 1/(128 * 256), 2/(128*256)
> >> + * ... 256/(128*256). So in order to program fine segment of LUT we
> >> + * need to pick every 8'th entry in LUT, and program 256 indexes.
> >> + * Fine segment's index 0 is programmed in HW, and it starts from
> >> + * index 1.
> > The wording here is a bit confusing. I guess the problem is what to call
> > things. PAL_PREC_INDEX[0/1] is what we program, but that maps to the point
> > seg2[1] with seg2[0] being unused by the hw. Well, the spec says it's
> > implicit but IIRC I was told long ago that it's not actually used.
> >
> > Not sure how to word that in the best way. Maybe something like?
> >
> > /*
> > * Fine segment (seg2) ...
> > *
> > * PAL_PREC_INDEX[0] and PAL_PREC_INDEX[1] map to seg2[1],
> > * with seg2[0] being unused by the hardware.
> > */
> >
> > Not sure that's any clearer.
> Ok, will try to come up with something in similar lines.
> >> + */
> >> + I915_WRITE(PREC_PAL_INDEX(pipe), PAL_PREC_AUTO_INCREMENT);
> >> + for (i = 1; i < 257; i++) {
> >> + entry = &lut[i * 8];
> >> + I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_12p4_udw(entry));
> >> + I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_12p4_ldw(entry));
> >> + }
> >> +
> >> + /*
> >> + * Coarse segment's starts from index 0 and it's step is 1/256 ie 0,
> >> + * 1/256, 2/256 ...256/256. As per the description of each entry in LUT
> >> + * above, we need to pick every 8 * 128 = 1024th entry in LUT, and
> >> + * program 256 of those.
> >> + */
> > Could make a note here stating that seg3[0] and seg3[1] are also unused
> > by the hardware, even though we have to program them to advance the
> > index. I don't see it mentioned in the spec, but this one I definitely
> > remember confirming from Art way back when. However I never verified
> > that on actual hw. We could also consider just programming those two
> > entries to 0 and start the actual coarse segment programming from index 2.
> > Or we could skip them by reprogramming the index directly.
> If they are not being used, does it matter what and if we program into
> them ? We can add a note though, mentioning this.
It shouldn't matter what we programing into them. But as mentioned I
never actually confirmed this on actual hardware. Would be nice to
double check that so we don't end up with incorrect comment.
> >> + for (i = 0; i < 256; i++) {
> >> + entry = &lut[i * 1024];
> > s/1024/8 * 128/ maybe?
>
> Sure.
>
> Regards
>
> Shashank
>
> >
> >> + I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_12p4_udw(entry));
> >> + I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_12p4_ldw(entry));
> >> + }
> >> +
> >> + icl_load_gcmax(crtc_state, entry);
> >> + ivb_load_lut_ext_max(crtc);
> >> +}
> >> +
> >> static void icl_load_luts(const struct intel_crtc_state *crtc_state)
> >> {
> >> const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
> >> @@ -775,10 +885,17 @@ static void icl_load_luts(const struct intel_crtc_state *crtc_state)
> >> if (crtc_state->base.degamma_lut)
> >> glk_load_degamma_lut(crtc_state);
> >>
> >> - if ((crtc_state->gamma_mode & GAMMA_MODE_MODE_MASK) ==
> >> - GAMMA_MODE_MODE_8BIT) {
> >> + switch (crtc_state->gamma_mode & GAMMA_MODE_MODE_MASK) {
> >> + case GAMMA_MODE_MODE_8BIT:
> >> i9xx_load_luts(crtc_state);
> >> - } else {
> >> + break;
> >> +
> >> + case GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED:
> >> + icl_program_gamma_superfine_segment(crtc_state);
> >> + icl_program_gamma_multi_segment(crtc_state);
> >> + break;
> >> +
> >> + default:
> >> bdw_load_lut_10(crtc, gamma_lut, PAL_PREC_INDEX_VALUE(0));
> >> ivb_load_lut_ext_max(crtc);
> >> }
> >> @@ -1209,7 +1326,7 @@ static u32 icl_gamma_mode(const struct intel_crtc_state *crtc_state)
> >> crtc_state_is_legacy_gamma(crtc_state))
> >> gamma_mode |= GAMMA_MODE_MODE_8BIT;
> >> else
> >> - gamma_mode |= GAMMA_MODE_MODE_10BIT;
> >> + gamma_mode |= GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED;
> >>
> >> return gamma_mode;
> >> }
> >> --
> >> 2.17.1
--
Ville Syrjälä
Intel
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