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

[Hanjun Guo]

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 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.

Thanks
Hanjun