Re: [PATCH v2] soc: imx8m: Probe the SoC driver as platform driver

[Marek Vasut]

On 9/26/24 7:36 PM, Saravana Kannan wrote:
> On Wed, Sep 25, 2024 at 11:28 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > On Wed, Sep 25, 2024, at 22:04, Marek Vasut wrote:
> > > With driver_async_probe=* on kernel command line, the following trace is
> > > produced because on i.MX8M Plus hardware because the soc-imx8m.c driver
> > > calls of_clk_get_by_name() which returns -EPROBE_DEFER because the clock
> > > driver is not yet probed. This was not detected during regular testing
> > > without driver_async_probe.
> > >
> > > Convert the SoC code to platform driver and instantiate a platform device
> > > in its current device_initcall() to probe the platform driver. Rework
> > > .soc_revision callback to always return valid error code and return SoC
> > > revision via parameter. This way, if anything in the .soc_revision callback
> > > return -EPROBE_DEFER, it gets propagated to .probe and the .probe will get
> > > retried later.
> >
> > Thanks for the new version, that was quick!
> >
> > > +static struct platform_driver imx8m_soc_driver = {
> > > +     .probe = imx8m_soc_probe,
> > > +     .driver = {
> > > +             .name = "imx8m-soc",
> > > +     },
> > > +};
> > > +module_platform_driver(imx8m_soc_driver);
> > > +
> > > +static int __init imx8_soc_init(void)
> > > +{
> > > +     struct platform_device *pdev;
> > > +
> > > +     pdev = platform_device_register_simple("imx8m-soc", -1, NULL, 0);
> > > +
> > > +     return IS_ERR(pdev) ? PTR_ERR(pdev) : 0;
> > > +}
> > >   device_initcall(imx8_soc_init);
> >
> > Did you run into problems with the method I suggested first?
> >
> > I don't like the way that this version still registers both the
> > device and driver regardless of the hardware it runs on, I'd
> > prefer to leave the platform check in the initcall and
> > only register them if we are actually on an imx8 machine.
> >
> > Having two initcalls also makes it impossible to build this
> > as a loadable module, which is why I suggested
> > platform_create_bundle().
>
> That particular helper doesn't seem to like probe deferral because it
> allows for some of the code to be in init sections. So, it gets
> dropped after module load is complete. So, Marek will still have to
> register the device and driver separately. But I agree that it might
> be better to NOT register the device and driver if the basic
> conditions aren't met.
Fixed in V3.