Re: [PATCH] i2c: omap: implement bus recovery

[Felipe Balbi <balbi@ti.com>]

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On Fri, Apr 10, 2015 at 11:41:22PM +0200, Wolfram Sang wrote:
> On Thu, Feb 19, 2015 at 12:06:49PM -0600, Felipe Balbi wrote:
> > If either SCL or SDA are stuck low, we need to
> > recover the bus using the procedure described
> > on section 3.1.16 of the I2C specification.
> > 
> > Note that we're trying to implement the procedure
> > exactly as described by that section. First we
> > check which line is stuck low, then implement
> > one or the other procedure. If SDA recovery procedure
> > fails, we reset our IP in an attempt to make it work.
> > 
> > Signed-off-by: Felipe Balbi <balbi@ti.com>
> 
> As Grygorii already mentioned: can you convert it to the standard i2c
> bus recovery mechanism?
> 
> And is the timeout you replace with the recovery caused by SDA stuck
> high (check the thread starting with
> http://thread.gmane.org/gmane.linux.kernel/1841371/focus=22435)

SDA stuck low is one reason, yes. There could be other reasons like the
far end (i2c client) just crapping out. I know of one touchscreen
controller which will just die if you continuously try to read from
unexistent registers. It will NAK for a while and later just die,
completely. The only way to recover from that today is resetting the
board. I have a feeling that resetting the touch controller might be
doable if we have a reset pin tied to a GPIO, haven't tried that yet. In
any case this is off-topic.

I'll rebase the patch and fix what you asked, then retest, and resend.

-- 
balbi

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