Re: [PATCH v13 7/9] ACPI: Translate the I/O range of non-MMIO devices before scanning

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Thu, Feb 15, 2018 at 12:47:25PM +0100, Rafael J. Wysocki wrote:
> On Thu, Feb 15, 2018 at 12:19 PM, John Garry <john.garry@huawei.com> wrote:
> >> Nothing apart from only being used by arm64 platforms today, which is
> >> circumstantial.
> >>
> >>>
> >>> I understand you need to find a place to add the:
> >>>
> >>> acpi_indirect_io_scan_init()
> >>>
> >>> to be called from core ACPI code because ACPI can't handle probe
> >>> dependencies in any other way but other than that this patch is
> >>> a Hisilicon ACPI driver - there is nothing generic in it (or at
> >>> least there are no standard bindings to make it so).
> >>>
> >>> Whether a callback from ACPI core code (acpi_scan_init()) to a driver
> >>> specific hook is sane or not that's the question and the only reason
> >>> why you want to add this in drivers/acpi/arm64 rather than, say,
> >>> drivers/bus (as you do for the DT driver).
> >>>
> >>> I do not know Rafael's opinion on the above, I would like to help
> >>> you make forward progress but please understand my concerns, mostly
> >>> on FW side.
> >>>
> >>
> >> I did mention an alternative in my "ping" in v12 patch 7/9 (Feb 1), but
> >> no response to this specific note so I kept on the same path.
> >>
> >> Here's what I then wrote:
> >> "I think another solution - which you may prefer - is to avoid adding
> >> this scan handler (and all this other scan code) and add a check like
> >> acpi_is_serial_bus_slave() [which checks the device parent versus a list
> >> of known indirectIO hosts] to not enumerate these children, and do it
> >> from the LLDD host probe instead (https://lkml.org/lkml/2017/6/16/250)"
> >>
> >
> > Hi Rafael, Lorenzo,
> >
> > I can avoid adding the scan handler in acpi_indirectio.c by skipping the
> > child enumeration, like with this change in scan.c:
> >
> > +static const struct acpi_device_id indirect_io_hosts[] = {
> > +    {"HISI0191", 0},    /* HiSilicon LPC host */
> > +    {},
> > +};
> > +
> > +static bool acpi_is_indirect_io_slave(struct acpi_device *device)
> > +{
> 
> Why don't you put the table definition here?
> 
> > +    struct acpi_device *parent = dev->parent;
> > +
> > +    if (!parent || acpi_match_device_ids(parent, indirect_io_hosts))
> > +        return false;
> > +
> > +    return true;
> 
> return parent && !acpi_match_device_ids(parent, indirect_io_hosts);
> 
> > +}
> > +
> >  static bool acpi_is_serial_bus_slave(struct acpi_device *device)
> >  {
> >      struct list_head resource_list;
> >      bool is_serial_bus_slave = false;
> >
> > +    if (acpi_is_indirect_io_slave(device))
> > +        return true;
> > +
> >      /* Macs use device properties in lieu of _CRS resources */
> >
> >
> > This means I can move all this scan code into the LLDD.
> >
> > What do you think? Please let me know.
> 
> If Lorenzo agrees, that will be fine by me modulo the above remarks.

I agree and I thank you for accepting this in core ACPI code, I think
that's much cleaner than a driver specific scan hook.

It is a shame we do not have a generic identifier for such bus in ACPI
but that won't happen overnight anyway (if ever, I think a binding for
LPC in the ACPI specs is hard to justify).

Thank you,
Lorenzo