Re: [PATCH] I2C: Fix twl4030 timeouts on omap3430

[Tony Lindgren <tony@atomide.com>]

* Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com> [080401 16:01]:
> On Tue, Apr 01, 2008 at 03:43:56PM +0300, ext Tony Lindgren wrote:
> > * Tony Lindgren <tony@atomide.com> [080331 17:30]:
> > > * Tony Lindgren <tony@atomide.com> [080331 13:43]:
> > > > * Tony Lindgren <tony@atomide.com> [080328 10:41]:
> > > > > Hi all,
> > > > > 
> > > > > This helps with the annoying I2C timeouts. Does anybody have an idea
> > > > > why the twl4030 chip does not like doing multiple transfers in a row?
> > > > > 
> > > > > To me the only difference seems to be that clocks are idled between
> > > > > writing the twl4030 register and reading the register value.
> > > > 
> > > > I'll push this today with a REVISIT comment added.
> > > 
> > > Looks like this kills twl4030 interrupts, so I've reverted it.
> > 
> > After looking into this problem a bit more, looks like twl4030 reads
> > to anything in "POWER ID" (modules 0x10 and higher) will hang twl4030
> > eventually and I2C controller gets stuck in mode where STP never clears.
> > 
> > Repeated reads to "USB ID", "AUD ID" or "AUX ID" will not hang twl4030.
> > 
> 
> I remember seeing something similar when doing the powerbutton code. 
> Klaus Pedersen found out that leaving CFG_BOOT to its reset value solved
> the problem. Unfortunately this breaks MADC and USB afaics, so it's not
> a real solution. CFG_BOOT is programmed in power_companion_init().

Great, this helped a lot! Looks like power_companion_init() tries to get
osc_ck without checking for clkg_get() return value, and osc_ck does not
exist in clock34xx.h. So R_CFG_BOOT gets set to default 26MHz value :)

Will post a patch when available.

Tony