[PATCH v2 01/12] ACPI/IORT: Make iort_match_node_callback walk the ACPI namespace for NC

[Lorenzo Pieralisi]

On Mon, Jun 29, 2020 at 12:24:43PM +0800, Hanjun Guo wrote:
> Hi Lorenzo,
> 
> On 2020/6/19 16:20, Lorenzo Pieralisi wrote:
> > When the iort_match_node_callback is invoked for a named component
> > the match should be executed upon a device with an ACPI companion.
> > 
> > For devices with no ACPI companion set-up the ACPI device tree must be
> > walked in order to find the first parent node with a companion set and
> > check the parent node against the named component entry to check whether
> > there is a match and therefore an IORT node describing the in/out ID
> > translation for the device has been found.
> > 
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > Cc: Will Deacon <will at kernel.org>
> > Cc: Hanjun Guo <guohanjun at huawei.com>
> > Cc: Sudeep Holla <sudeep.holla at arm.com>
> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > Cc: Robin Murphy <robin.murphy at arm.com>
> > Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
> > ---
> >   drivers/acpi/arm64/iort.c | 20 ++++++++++++++++++--
> >   1 file changed, 18 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > index 28a6b387e80e..5eee81758184 100644
> > --- a/drivers/acpi/arm64/iort.c
> > +++ b/drivers/acpi/arm64/iort.c
> > @@ -264,15 +264,31 @@ static acpi_status iort_match_node_callback(struct acpi_iort_node *node,
> >   	if (node->type == ACPI_IORT_NODE_NAMED_COMPONENT) {
> >   		struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
> > -		struct acpi_device *adev = to_acpi_device_node(dev->fwnode);
> > +		struct acpi_device *adev;
> >   		struct acpi_iort_named_component *ncomp;
> > +		struct device *nc_dev = dev;
> > +
> > +		/*
> > +		 * Walk the device tree to find a device with an
> > +		 * ACPI companion; there is no point in scanning
> > +		 * IORT for a device matching a named component if
> > +		 * the device does not have an ACPI companion to
> > +		 * start with.
> > +		 */
> > +		do {
> > +			adev = ACPI_COMPANION(nc_dev);
> > +			if (adev)
> > +				break;
> > +
> > +			nc_dev = nc_dev->parent;
> > +		} while (nc_dev);
> 
> I'm lost here, we need the ACPI_COMPANION (the same as
> to_acpi_device_node()) of the device, but why do we need to go
> up to find the parent node?

For devices that aren't described in the DSDT - IORT translations
are determined by their ACPI parent device. Do you see/Have you
found any issue with this approach ?

> For a platform device, if I use its parent's full path name for
> its named component entry, then it will match, but this will violate
> the IORT spec.

Can you elaborate on this please I don't get the point you
are making.

Thanks,
Lorenzo