Re: [RFC PATCH for Juno 1/2] net: smsc911x add support for probing from ACPI

[Catalin Marinas <catalin.marinas@arm.com>]

On Mon, Sep 01, 2014 at 06:32:45PM +0100, Graeme Gregory wrote:
> On Mon, Sep 01, 2014 at 07:11:44PM +0200, Arnd Bergmann wrote:
> > On Monday 01 September 2014 18:04:47 Catalin Marinas wrote:
> > > On Mon, Sep 01, 2014 at 04:06:00PM +0100, Hanjun Guo wrote:
> > > > +#ifdef CONFIG_ACPI
> > > > +/* Configure some sensible defaults for ACPI mode */
> > > > +static int smsc911x_probe_config_acpi(struct smsc911x_platform_config *config,
> > > > +                                 acpi_handle *ahandle)
> > > > +{
> > > > +     if (!ahandle)
> > > > +             return -ENOSYS;
> > > > +
> > > > +     config->phy_interface = PHY_INTERFACE_MODE_MII;
> > > > +
> > > > +     config->flags |= SMSC911X_USE_32BIT;
> > > > +
> > > > +     config->irq_polarity = SMSC911X_IRQ_POLARITY_ACTIVE_HIGH;
> > > > +
> > > > +     config->irq_type = SMSC911X_IRQ_TYPE_PUSH_PULL;
> > > > +
> > > > +     return 0;
> > > > +}
> > > > +#else
> > > 
> > > I don't like this and it shows issues we have with ACPI on certain ARM
> > > platforms. You hard-code these values to match the Juno platform. What
> > > if we get another SoC which has different configuration here? For DT, we
> > > have the smsc911x_probe_config_dt() which reads the relevant information
> > > from DT. I think this kind of configuration would be more suitable as
> > > _DSD properties and sharing the similar names with DT (but we go back to
> > > the question about who's in charge of the _DSD properties).
> > 
> > Good point, I totally missed that.
> > 
> > There is of course the possibility to set those values based on the
> > acpi_device_id, but that is exactly the part that _DSD is trying to
> > avoid.
> 
> This will of course most likely be replaced by _DSD values. I just
> hardcoded for now as _DSD is not yet in the kernel and issues around
> maintenance of bindings are not solved (unless this happened at KS where
> I was not present).

Not much at the KS, I think it will need to be followed up on lkml
(https://lkml.org/lkml/2014/8/17/10 is the last I'm aware of, not sure
about any updates in the meantime).

While the above gets sorted, what's the position from an ARM
perspective (and covered by Documentation/arm64/arm-acpi.txt)? I think
the "Device Enumeration" section in this document is fine, it's just the
kernel infrastructure missing.

Alternatively, you can say _DSD is not allowed (yet?) but I don't
particularly like basing the configuration on acpi_device_id like in
this patch. Which would leave us with ignoring any SoC containing
devices that require such specific configuration.

-- 
Catalin