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videomixer: compute best m/d value for pixel clock synthesizer

This commit is contained in:
Sebastien Bourdeauducq 2013-11-11 21:30:12 +01:00
parent 132b6ce87d
commit c8da400af0
1 changed files with 25 additions and 4 deletions
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29
software/videomixer/processor.c
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@ -1,4 +1,5 @@
#include <stdio.h> #include <stdio.h>
#include <stdlib.h>
#include <hw/csr.h> #include <hw/csr.h>
#include <hw/flags.h> #include <hw/flags.h>
@ -62,11 +63,31 @@ static void fb_clkgen_write(int cmd, int data)
while(fb_driver_clocking_status_read() & CLKGEN_STATUS_BUSY); while(fb_driver_clocking_status_read() & CLKGEN_STATUS_BUSY);
} }
static void fb_get_clock_md(unsigned int pixel_clock, unsigned int *m, unsigned int *d) static void fb_get_clock_md(unsigned int pixel_clock, unsigned int *best_m, unsigned int *best_d)
{ {
// TODO unsigned int ideal_m, ideal_d;
*m = 13; unsigned int bm, bd;
*d = 10; unsigned int m, d;
unsigned int diff_current;
unsigned int diff_tested;
ideal_m = pixel_clock;
ideal_d = 5000;
bm = 1;
bd = 0;
for(d=1;d<=256;d++)
for(m=2;m<=256;m++) {
/* common denominator is d*bd*ideal_d */
diff_current = abs(d*ideal_d*bm - d*bd*ideal_m);
diff_tested = abs(bd*ideal_d*m - d*bd*ideal_m);
if(diff_tested < diff_current) {
bm = m;
bd = d;
}
}
*best_m = bm;
*best_d = bd;
} }
static void fb_set_mode(const struct video_timing *mode) static void fb_set_mode(const struct video_timing *mode)