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Turns out the VLV/CHV fixed function sprite CSC expects full range data as input. We've been feeding it limited range data to it all along. To expand the data out to full range we'll use the color correction registers (brightness, contrast, and saturation). On CHV pipe B we were actually doing the right thing already because we progammed the custom CSC matrix to do expect limited range input. Now that well pre-expand the data out with the color correction unit, we need to change the CSC matrix to operate with full range input instead. This should make the sprite output of the other pipes match the sprite output of pipe B reasonably well. Looking at the resulting pipe CRCs, there can be a slight difference in the output, but as I don't know the formula used by the fixed function CSC of the other pipes, I don't think it's worth the effort to try to match the output exactly. It might not even be possible due to difference in internal precision etc. One slight caveat here is that the color correction registers are single bufferred, so we should really be updating them during vblank, but we still don't have a mechanism for that, so just toss in another FIXME. v2: Rebase v3: s/bri/brightness/ s/con/contrast/ (Shashank) v4: Clarify the constants and math (Shashank) Cc: Harry Wentland <harry.wentland@amd.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Daniel Stone <daniel@fooishbar.org> Cc: Russell King - ARM Linux <linux@armlinux.org.uk> Cc: Ilia Mirkin <imirkin@alum.mit.edu> Cc: Hans Verkuil <hverkuil@xs4all.nl> Cc: Shashank Sharma <shashank.sharma@intel.com> Cc: Uma Shankar <uma.shankar@intel.com> Cc: Jyri Sarha <jsarha@ti.com> Cc: "Tang, Jun" <jun.tang@intel.com> Reported-by: "Tang, Jun" <jun.tang@intel.com> Cc: stable@vger.kernel.org Fixes: 7f1f3851feb0 ("drm/i915: sprite support for ValleyView v4") Reviewed-by: Shashank Sharma <shashank.sharma@intel.com> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180214192327.3250-5-ville.syrjala@linux.intel.com
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.