Messages in this thread | | | Date | Thu, 10 Aug 2006 16:19:26 +0300 | From | Tony Lindgren <> | Subject | Re: [PATCH] OMAP: I2C driver for TI OMAP boards #3 |
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* Jean Delvare <khali@linux-fr.org> [060810 11:30]: > Hi Tony, Komal, > > > Hmmm, this sounds like a bug somewhere. TRM for 5912 says the I2C clock > > must be prescaled to be between 7 - 12 MHz [1]. The XOR input clock is > > typically 12, 13 or 19.2 MHz. So we should have code that produces: > > > > XOR Mhz Divider Prescaler > > 12 1 0 > > 13 2 1 > > 19.2 2 1 > > Not that 13 MHz cannot actually be prescaled between 7 and 12 MHz, no > matter how you look at it.
True :) But that's what the docs say..
> > Then again the original old code produces something different too [2]... > > > > I suspect the original code had some hw workarounds and and later code > > may have a conversion bug somewhere :) > > > > I suggest we keep the code as is for now since it's known to work on > > all omaps, and then submit a follow-up patch later once we have > > verified that that code based on the TRM works on all omaps. > > I've now taken Komal's patch (#4). Here is a proposed patch which brings > the prescaler computation formula in line with your comment and table > above. It could be applied on top of Komal's patch unless it causes a > problem on some of the OMAP systems. For XOR = 13 MHz, it changes the > prescaler from 0 to 1. For XOR = 19.2 MHz it changes the prescaler from > 2 to 1.
OK cool. As far as I'm concerned, I'm fine with it too: Signed-off-by: Tony Lindgren <tony@atomide.com>
> I don't have any hardware to test it, though. If it happens to be > better to be slightly over 12 MHz than slightly below 7 MHz, the > "> 12000000" condition below can be replaced with "> 14000000".
Thanks, we'll test it on various omaps and let you know if it works.
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