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    • Ville Syrjälä's avatar
      drm/i915: Add 10bit gamma mode for gen2/3 · 67630bac
      Ville Syrjälä authored 
      Some gen2/gen3 parts have a 10bit gamma mode, on some pipes.
Expose it.

The format is different to the later i965+ style in that we
store a 10bit value and a 6 bit floating point slope for each
entry. Ie. the hardware extrapolates the intermediate steps
from the current LUT entry, instead of interpolating between
the current and next LUT entries. This also means we don't store
the last LUT entry in any register as it is defined by the previous
LUT entry's value+slope.

The slope has limited precision though (2 bit exponent + 4 bit
mantissa), so we'd have to allow for more error in the state checker
for the last entry and we have to make sure userspace doesn't
pass in something where the slope is simply to steep. In theory
we should perhaps check the slope for every interval, but we don't
do that for any other interpolated gamma mode and I suspect they
may also have some internal limit on the slope. I haven't confirmed
that theory though. Anyways, for ease of implementation we shall
just ignore the last entry in the state checker. If all the other
entries match anyway then that seems like a good indication that
the hardware was programmed as expected.

v2: Redo the state checker logic a bit
    Rebase due to other changes
v3: Fix C8 readout
v4: Use REG_FIELD_PREP()
Acked-by: default avatarUma Shankar <uma.shankar@intel.com>
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221114153732.11773-20-ville.syrjala@linux.intel.com
      67630bac
    • Ville Syrjälä's avatar
      drm/i915: Use gamma LUT for RGB limited range compression · 07fc6a7b
      Ville Syrjälä authored 
      On hsw+ and glk class hardware we current make a mess of
things when we have to both generate limited range output
and use the hw gamma LUT. Since we do the range compression
using the pipe CSC unit (which is situated before the gamma
LUT in the pipe) we are in fact applying the gamma to the
limited range data instead of the full range data as the
user intended.

We can work around this by applying the range compression
via the gamma LUT instead of using the pipe CSC for it.
Fairly easy to do now that we have the internal post_csc_lut
attachment point where we can stick our new cooked LUT.

On hsw+ this only needs to be done when using the split
gamma mode or when the ctm is enabled since otherwise we can
simply reorder the LUT vs. CSC. On glk we need to do this any
time a gamma LUT is used since no reordering is possible.
We do lose a bit of coverage in intel_color_assert_luts(),
but so be it.
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221114153732.11773-19-ville.syrjala@linux.intel.comReviewed-by: default avatarUma Shankar <uma.shankar@intel.com>
      07fc6a7b
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