Re: [PATCH 2/4] i2c: rockchip: ignore i2c transfers when another transfer is running

[Sascha Hauer <sha@pengutronix.de>]

On Fri, Sep 08, 2023 at 01:51:32PM +0200, Sascha Hauer wrote:
> On Fri, Sep 08, 2023 at 12:16:47PM +0200, Gerald Loacker wrote:
> > It may happen that an i2c transfer is requested by a callback although
> > there is an other i2c transfer running. In this case do not interrupt the
> > transfer and return with an error.
> > 
> > Signed-off-by: Gerald Loacker <gerald.loacker@wolfvision.net>
> > ---
> >  drivers/i2c/busses/i2c-rockchip.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-rockchip.c b/drivers/i2c/busses/i2c-rockchip.c
> > index 1bca3e9913..a869b9d0b7 100644
> > --- a/drivers/i2c/busses/i2c-rockchip.c
> > +++ b/drivers/i2c/busses/i2c-rockchip.c
> > @@ -369,7 +369,19 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> >  {
> >  	struct rk_i2c *i2c = to_rk_i2c(adapter);
> >  	struct device *dev = &adapter->dev;
> > -	int i, ret = 0;
> > +	struct i2c_regs *regs = i2c->regs;
> > +	int i, ret = 0, val;
> > +
> > +	val = readl(&regs->con);
> > +	if (val & I2C_CON_EN) {
> > +		val = readl(&regs->con);
> > +		if (val & I2C_IPD_ALL_CLEAN) {
> > +			dev_dbg(dev,
> > +				"i2c_xfer: %d messages dropped due to pending interrupts\n",
> > +				nmsgs);
> > +			return -EAGAIN;
> > +		}
> > +	}
> 
> Can you have a look how this can happen? Normally this should only
> happen if you have a heartbeat LED behind a I2C GPIO expander or some
> other unusual setup. Adding a dump_stack() next to the dev_dbg() call
> might give a clue.

I just realized you sent some ksz9477 along with this series. Are you
using that in I2C mode? In that case it could be the periodic link check
that does I2C accesses in the background.

Sascha

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