[U-Boot-Users] Board init

Adam Bezanson
2003-03-05T02:20:05Z

This is an interesting topic, because I am actually
seeing I2C bus hangs on our own custom hardware
once and a great while. This hardware is PowerPC
based but doesn't use u-boot. I kind of narrowed
it down to the processor getting reset during
an I2C transaction. Since the slave device (EEPROM with a temp
sensor in it) doesn't have a reset, the bus gets stuck
low and when a master tries to start a new transaction
it can't because the bus appears busy.

Which line did you attach a GPIO pin to? The clock or the data?
It seems that this would be a good generic solution to this
particular part of the problem to simply clock the slaves back to
a known state. I'm not sure if I've seen corruption as mentioned in the
I2C_Edge_Conditions doc.

I was thinking, in my design, since I have independent control of the
reset to the processor subsystem in hardware, To make the code set a bit
which gates the reset to the processor subsystem while doing I2C accesses.
When the access(es) finish the bit would be cleared and then the reset would
be
allowed to take effect. This of course is very hardware specific, but just a
thought
I had.

Adam

-----Original Message-----
From: u-boot-users-admin@lists.sourceforge.net
[mailto:u-boot-users-admin at lists.sourceforge.net]On Behalf Of Robert
Schwebel
Sent: Tuesday, March 04, 2003 10:58 AM
To: U-Boot Mailing List
Subject: Re: [U-Boot-Users] Board init

On Tue, Mar 04, 2003 at 04:27:24PM +0100, Wolfgang Denk wrote:
> Are you refering to the I2C Edge Conditions propblem? (You _did_ read
> the doc/I2C_Edge_Conditions files, didn't you?)

Nope, but that seems to be what we also see :-)

> Seems you are (at least) the second person who got bitten by this
> probem, so we should probably add a generic solution that will fix
> this problem in all cases.
>
> Can you come up with a generic solution?

I'll try something.

Robert
--
Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de
Pengutronix - Linux Solutions for Science and Industry
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