Re: [PATCH] i2c: tegra: Check for overflow errors with BUG_ON.

From: Felipe Balbi
Date: Mon Aug 15 2011 - 16:04:06 EST


On Mon, Aug 15, 2011 at 12:52:36PM -0700, Doug Anderson wrote:
> Felipe,
> On Mon, Aug 15, 2011 at 12:17 PM, Felipe Balbi <balbi@xxxxxx> wrote:
> > so due to a FIFO overflow you lock up the whole system ? Can't you e.g.
> > reset the controller and reconfigure it rather than locking up the
> > system ?
> Certainly we could try to be more proactive and reset / retry / return
> the error to the client. However, since the only expected situation
> where this BUG_ON should hit is due to a bug in this driver itself
> (AKA: i2c clients shouldn't be able to do anything to cause the BUG_ON
> to hit), that seems like a lot of added complexity.

so at least just pass an error to the client, but hanging the entire
system seems a bit too much, dont you think ?

> Also: if there is an arbitrary software bug that causing an overflow
> condition to occur, I'm not sure how stable the system will be.
> Specifically, the i2c controller is used (among other things) to talk
> to the PMU and adjust voltages in the system. If we just sent it a
> random command, I'd rather report the bug right away so we don't get
> hard to find/reproduce failures in other parts of the system.

that's a good point, I still think that e.g. making a cellphone
unresponsive until a watchdog reset triggers just because you got a FIFO
overflow on the I2C controller is too much.


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