[U-Boot-Users] i2c compiling and/or linking problem - solved (for the archive)

Wolfgang Denk wd at denx.de
Fri Feb 11 18:33:41 CET 2005

In message <420CCAFE.3000004 at smiths-aerospace.com> you wrote:
> Trivia: I2C on the 82xx and, IIRC, 8xx family is actually done in 
> software (microcode in the CPM) and is horribly inefficient in terms of 
> CPM resources (not that that matters for u-boot).

Well, it DOES matter.

If you need to access data in U-Boot, you most probably will want  to
access  the  same data in Linux, too. If not now, then with your next
software update. We just had a case where a  customer  ran  into  I2C
problems  during  shutdown  of the system - he tried to save a lot of
data to an IDE device connected to the PCMCIA controller, and  to  an
EEPROM on the I2C bus. We got lots of lost IDE interrupts because the
PCMCIA  controller  died again and again when the CPM got overloaded,
and we got lots of I2C errors - it turned out that writing just a few
bytes to EEPROM ran into a timeout which was set to a  generous  full
second. Unfortunately, the CPM needed more than 3 seconds (!) in some
cases to complete the I2C request.

I really dislike I2C, especially when used to store data like  in  an

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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That's what makes it a thing to be avoided.
	-- Kirk, "A Taste of Armageddon", stardate 3193.0

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