cirrusfb: do not change MCLK for Alpine chips
A memory clock value (MCLK) is changed to a minimum required by a current mode bandwidth. This usually lowers the MCLK to its minimum (50 MHz) thus decreasing the card performance. Just leave the MCLK value set by card BIOS. The CL-GD5446 Technical Reference Manual point 9.9.1.3 states that if a pixclock value is close (~1%) to the MCLK or MCLK/2 this may result in a jitter on the screen. A countermeasure is to use the MCLK as pixclock source instead of a VCLK. The patch implements this as well. Signed-off-by: NKrzysztof Helt <krzysztof.h1@wp.pl> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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