67630bacae
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: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221114153732.11773-20-ville.syrjala@linux.intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.