soc: imx: gpcv2: removing and probing fails

[Andrey Smirnov]

On Sun, Jan 7, 2018 at 2:48 AM, Stefan Agner <stefan at agner.ch> wrote:
> Hi Andrew,
>
> I noticed that the driver fails when removing and probing again. As far
> as I can see due to duplicate add of the platform devices.
>
> As far as I can tell the driver should register the remove callback and
> do a platform_device_unregister on the newly created platform devices.
> However, as far as I can tell we don't hold on to a reference to them...
> I guess we could keep references in imx_gpcv2_probe, but maybe there is
> an easier way?

Stefan:

Good catch and sorry for the inconvenience. I just spent a little bit
of time repro-ing this and it looks like there are two separate bugs,
actually. First one, as you correctly pointed out, is due to
re-registration of pm-domain platform drivers. That, however, should
only result in a WARNING and a failed driver probing, not in a killed
init due to BUG. So the second one, that BUG message in the stack
trace, is due to the fact that I incorrectly provide statically
allocated data via dev.platform_data and it ends up being kfree'd in
platform_device_release().

IMHO, this driver isn't really meant to be removed, so the simplest
solution to the first problem would be to specify
"imx_gpc_driver.driver.suppress_bind_attrs = true" and remove any
option to remove the driver, but I don't know if that's acceptable or
not.

Shawn, would the above be acceptable upstream?

Solution for bug #2 is trivial and I'll send patches for both once we
agree how to fix #1.

Thanks,
Andrey Smirnov

P.S: Also, since I based my code on gpc.c, I suspect that driver will
have exactly the same problem (I'll do some experiments to confirm)