OMAPDSS: DISPC: Update Fir Coefficients
The FIR coefficients present in kernel are being updated to new coefficients consisting of 24 coefficient tables, with 12 each for 3 tap and 5 tap scenario, which are chosen on the basis of DISPC up/downsampling filters M value. M is the inverse of low pass cut off frequency of the sampling filter. For vertical scaling 3 tap or 5 tap tables are used based on the clock rate and width of the line buffer whereas in OMAP2 3 tap is always used. For horizontal scaling however 5 tap tables are always used. New coefficients and the corresponding logic have been tested on OMAP2, OMAP3 and OMAP4. Horizontal and vertical scaling worked fine except for some 3 tap vs 5 tap issue during vertical upscaling and clock failing issues which is acknowledged in the next patch. Vertical upscaling was found to perform better under 5 taps. The 24 coefficient tables have been moved to another file dispc_coefs.c for proper maintainance. This code is written based on code written by Lajos Molnar <lajos@ti.com> in Android Kernel for scaling. Lajos Molnar <lajos@ti.com> had fine tuned the FIR coefficient selection process and reduced outliness and blockiness around images when upscaling more than 2 times. Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
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