[U-Boot] [PATCH] Coldfire: I2C: Update I2CFDR frequency divider 0x0E value from 192 to 204

[TC Liew]

Richard,

Nak.

The divider and fdr value are predefined in the 5271 reference manual.

The bus clock is 50Mhz and the CONFIG_SYS_I2C_SPEED is set to 80000.

divider = min(i2c_clk / speed, (unsigned short) -1);
divider = 50000000 / 80000;
          = 625

if (fsl_i2c_speed_map[i].divider >= divider), here is looking for any
divider that is larger or equal to 625.
{640, 21} is the closer match.

Regards,
TsiChung

On Thu, Mar 19, 2009 at 2:47 AM, Heiko Schocher <hs at denx.de> wrote:
>
> Hello Richard,
>
> Richard Retanubun wrote:
> >  From 9a7a9dfb1ed367b275bc19f7c40c98b63de75fb2 Mon Sep 17 00:00:00 2001
> > From: Richard Retanubun <RichardRetanubun at RuggedCom.com>
> > Date: Wed, 18 Mar 2009 12:52:35 -0400
> > Subject: [PATCH] Update I2CFDR frequency divider 0x0E value from 192 to 204.
> >
> > This patch changes the divider factor of 14 for I2CFDR.
> > Through empirical experiments on a M5271EVB with a 25MHz osc,
> > multiplied to 75MHz system frequency, the divider 0x0E that is
> > supposed to be div-by-192, results in i2c clock of ~376 KHz
> > (which is ~div-by-204). Using the alternate divider for div-by-192
> > (49) results in an i2c clock of ~390 KHz, a better clock approximation.
> >
> > Signed-off-by: Richard Retanubun <RichardRetanubun at RuggedCom.com>
> > ---
> >   drivers/i2c/fsl_i2c.c |    4 ++--
> >   1 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
> > index ce646fd..c61bf84 100644
> > --- a/drivers/i2c/fsl_i2c.c
> > +++ b/drivers/i2c/fsl_i2c.c
> > @@ -113,8 +113,8 @@ static const struct {
> >       {56, 41}, {64, 42}, {68, 7}, {72, 43},
> >       {80, 8}, {80, 44}, {88, 9}, {96, 41},
> >       {104, 10}, {112, 42}, {128, 11}, {128, 43},
> > -     {144, 12}, {160, 13}, {160, 48}, {192, 14},
> > -     {192, 49}, {224, 50}, {240, 15}, {256, 51},
> > +     {144, 12}, {160, 13}, {160, 48}, {192, 49},
> > +     {204, 14}, {224, 50}, {240, 15}, {256, 51},
> >       {288, 16}, {320, 17}, {320, 52}, {384, 18},
> >       {384, 53}, {448, 54}, {480, 19}, {512, 55},
> >       {576, 20}, {640, 21}, {640, 56}, {768, 22},
> >
>
> Because I think this will go through the coldfire tree, you have my:
>
> Acked-by: Heiko Schocher <hs at denx.de>
>
> bye
> Heiko
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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