[U-Boot] fsl_i2c: increase I2C timeout values and make them configurable

[Joakim Tjernlund]

Timur Tabi <timur at freescale.com> wrote on 10/09/2009 18:13:03:
>
> Joakim Tjernlund wrote:
>
> > This calculation does not seem to match AN2919.
>
> When I wrote the code, AN2919 was much smaller than what you have today.
>
> > Suppose one used only Table 7(almost what we have if you exclude dfsr!= 1)
> > Table 7 is valid for 1 <= dfsr <=5 so how about replacing the current dfsr
> > with:
> > #ifdef __PPC__
> >          u8 dfsr;
> >          dfsr = (5*(i2c_clk/1000))/(100000);
> >          if (dfsr > 5)
> >             dfsr = 5;
> >          if (!dfsr)
> >             dfsr = 1;
> >          debug("i2c_clk:%d, dfsr:%d\n", i2c_clk, dfsr);
> >          writeb(dfsr, &dev->dfsrr);   /* set default filter */
> > #endif
>
> The value of FDR is dependent on the value of DFSR, so if I calculate DFSR, I
> have to also calculate FDR.  This means the table goes away.  I'm okay with
> that (since my table is no longer a viable approach, it seems), but it's more
> work than I'm willing to do at the moment.  Especically since this is going to
> need a lot of testing before I'm willing to push it.

I could not resist so I did a quick start:
#include <stdlib.h>
#include <stdio.h>
#define I2C_CLK 133332000
int main(int argc, char *argv[])
{
  unsigned long A,B,C;
  unsigned long divisor, req_div;
  unsigned long curr_div = ~0;
  unsigned long speed;

  if (argc != 2) {
    printf("%s <speed in HZ>\n", argv[0]);
    exit(1);
  }
  speed = atol(argv[1]);
  req_div = I2C_CLK/speed;
  C = (5*(I2C_CLK/1000))/(100000);
  if (!C)
    C = 1;

  for(A=10;A <= 30; A+=2) {
    for (B=16; B<=2048;B*=2) {
      divisor = B * (A + (3*C/B)*2);
      if (divisor > req_div && divisor < curr_div) {
	printf("div:%d, A:%d, B:%d\n", divisor, A, B);
	curr_div = divisor;
      }
    }
    if (A == 20)
      A+=2;
    if (A == 24)
      A+=4;
  }
  printf("\nreq_div:%d, curr_div:%d, DFSR:%d\n", req_div, curr_div, C);
}

This should be useful I hope. The special treatment for A == 20 and A == 24
is a bit strange though, do they really jump like that?

     Jocke