pca953x: Probing too early

[Andy Shevchenko]

On Wed, Aug 21, 2024 at 12:29 AM Andrew Lunn <andrew at lunn.ch> wrote:
> On Tue, Aug 20, 2024 at 05:47:27PM -0300, Fabio Estevam wrote:
> > Adding the i2c-folks on Cc.
> > On Tue, Aug 20, 2024 at 5:02 PM Fabio Estevam <festevam at gmail.com> wrote:

> > > I am seeing an issue with the PCA935X driver in 6.6.41 and
> > > 6.11.0-rc4-next-20240820.
> > >
> > > The pca953x is getting probed before its I2C parent (i2c-2):
> > >
> > > [    1.872917] pca953x 2-0020: supply vcc not found, using dummy regulator
> > > [    1.889195] pca953x 2-0020: using no AI
> > > [    1.893260] pca953x 2-0020: failed writing register
> > > [    1.898258] pca953x 2-0020: probe with driver pca953x failed with error -11
>
> -11 is EAGAIN, which is a bit odd. Given your description, i would of
> expected ENODEV. My guess is, it needs another resource, a GPIO,
> regulator, or interrupt controller. That resources might not of probed
> yet. If that is true, you want the pca953x_probe() to return
> -EPROBE_DEFER. The driver core will then try the probe again sometime
> later, hopefully when all the needed resources are available.
>
> Track down where the EAGAIN is coming from.

I bet on __i2c_smbus_xfer(). Which comes from
https://elixir.bootlin.com/linux/v6.11-rc4/source/drivers/i2c/busses/i2c-imx.c#L549.
Very easy to check is to add at the top of i2c-imx.c the following

#undef EAGAIN
#define EAGAIN __LINE__

and search for the respective line in suspicious files.

-- 
With Best Regards,
Andy Shevchenko