[PATCH 1/2] I2C: Set I2C timing registers for mxs-i2c
Marek Vasut
marex at denx.de
Mon Apr 30 16:47:17 EDT 2012
Dear Wolfram Sang,
> > > > > > This sets the bus to run at 400kHz, prior to this,
> > > > > > the bus frequency was undefined.
> > > > >
> > > > > Not exactly. The default values let it run at 100kHz.
> > > >
> > > > Have you tried dumping the default values and comparing it with the
> > > > values for 100kHz in the manual?
> > >
> > > Yes, sure. Doesn't it work for you? I just rechecked and the values are
> > > okay. That being said, if you make it configurable for 400kHz, it would
> > > in deed be better to rewrite the values for 100kHz, too.
> >
> > They were different for me ... did you configure the i2c bus in your
> > bootloader possibly? Those values might have been written there since
> > then ... I didn't run i2c in u-boot before booting linux.
>
> Nope, no I2C involved in the bootloader at all. Do you get the correct
> values after soft-resetting the device?
>
> It doesn't really matter, though. Just reinit them to the proper values
> depending on the user setting.
Indeed. Default to 100kHz might be a good idea too, in case user entered some
weird value. Eventually, it'd be nice if we could calculate the timing values
for all possible frequencies, but I didn't got to deriving such formula ...
dunno if it's worth it either, doubt so.
Best regards,
Marek Vasut
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