Re: [PATCH v4 37/38] platform/x86: intel_pmc_ipc: Convert to MFD

Lee Jones
2020-01-22T13:27:50Z

On Wed, 22 Jan 2020, Mika Westerberg wrote:

> On Wed, Jan 22, 2020 at 12:34:54PM +0000, Lee Jones wrote:
> > > +static int intel_pmc_probe(struct platform_device *pdev)
> > > +{
> > > + struct intel_scu_ipc_pdata pdata = {};
> > > + struct intel_pmc_dev *pmc;
> > > + int ret;
> > > +
> > > + pmc = devm_kzalloc(&pdev->dev, sizeof(*pmc), GFP_KERNEL);
> > > + if (!pmc)
> > > + return -ENOMEM;
> > > +
> > > + pmc->dev = &pdev->dev;
> > > + spin_lock_init(&pmc->gcr_lock);
> > > +
> > > + ret = intel_pmc_get_resources(pdev, pmc, &pdata);
> > > + if (ret) {
> > > + dev_err(&pdev->dev, "Failed to request resources\n");
> > > + return ret;
> > > + }
> > > +
> > > + pmc->scu = devm_intel_scu_ipc_register(&pdev->dev, &pdata);
> > > + if (IS_ERR(pmc->scu))
> > > + return PTR_ERR(pmc->scu);
> >
> > *_register is better than *_probe. If it was called that (or maybe
> > *_init) initially I may have missed the issue altogether ...
> >
> > However, I still think it the SCU IPC *device* needs to be a device
> > driver and abide by the rules, ensuring it uses the device driver
> > model/API. As such, it should be registered and probed as a device.
>
> Which type of device you suggest here? And which bus it should be
> registered to? I think we can make this create a platform_device but
> then we would need to do that from the PCI driver as well which seems
> unnecessary since we already have the struct pci_dev.

What kind of device is it?

Refrain from using platform device, unless it is one please.

> For instance in drivers/mfd/intel-lpss* we use similar approach (the
> core part is library that gets called by probe drivers (ACPI, PCI). We
> don't create any additional platform_devices.

That's different. Here the *-acpi.c and *-pci.c are only used as
registration hooks into the same device. The semantics we're
discussing are seemingly used to probe/init a different device in a
separate subsystem.

> There is another twist. Ideally we would like to see the SCU IPC probed
> and intialized before the MFD children so that we know the SCU IPC is
> ready by the time the children devices are created. I guess we could
> work it around by returning -EPROBE_DEFER but that does not feel right
> to be honest.

That's precisely what -EPROBE_DEFER was designed for.

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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