Re: [PATCH v6 05/14] ACPI: platform-msi: retrieve dev id from IORT

[Hanjun Guo]

Hi Lorenzo,

On 2017/1/5 3:18, Lorenzo Pieralisi wrote:
> On Mon, Jan 02, 2017 at 09:31:36PM +0800, Hanjun Guo wrote:
> > For devices connecting to ITS, it needs dev id to identify
> > itself, and this dev id is represented in the IORT table in
> > named componant node [1] for platform devices, so in this
> > patch we will scan the IORT to retrieve device's dev id.
> >
> > Introduce iort_pmsi_get_dev_id() with pointer dev passed
> > in for that purpose.
> >
> > [1]: https://static.docs.arm.com/den0049/b/DEN0049B_IO_Remapping_Table.pdf
> >
> > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> > Tested-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> > Tested-by: Majun <majun258@xxxxxxxxxx>
> > Tested-by: Xinwei Kong <kong.kongxinwei@xxxxxxxxxxxxx>
> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > ---
> >  drivers/acpi/arm64/iort.c                     | 26 ++++++++++++++++++++++++++
> >  drivers/irqchip/irq-gic-v3-its-platform-msi.c |  4 +++-
> >  include/linux/acpi_iort.h                     |  8 ++++++++
> >  3 files changed, 37 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > index 174e983..ab7bae7 100644
> > --- a/drivers/acpi/arm64/iort.c
> > +++ b/drivers/acpi/arm64/iort.c
> > @@ -444,6 +444,32 @@ u32 iort_msi_map_rid(struct device *dev, u32 req_id)
> >  }
> >
> >  /**
> > + * iort_pmsi_get_dev_id() - Get the device id for a device
> > + * @dev: The device for which the mapping is to be done.
> > + * @dev_id: The device ID found.
> > + *
> > + * Returns: 0 for successful find a dev id, errors otherwise
> > + */
> > +int iort_pmsi_get_dev_id(struct device *dev, u32 *dev_id)
> > +{
> > +	struct acpi_iort_node *node;
> > +
> > +	if (!iort_table)
> > +		return -ENODEV;
> > +
> > +	node = iort_find_dev_node(dev);
> > +	if (!node) {
> > +		dev_err(dev, "can't find related IORT node\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	if(!iort_node_get_id(node, dev_id, IORT_MSI_TYPE, 0))
>
> I disagree with this approach. For named components we know that
> there are always two steps involved (second optional):
>
> (1) Retrieve the initial id (this may well provide the final mapping)
> (2) Map the id (optional if (1) represents the map type we need)
>
> That's the reason why I kept iort_node_get_id() and iort_node_map_rid()
> separated.
>
> Now, what we can do is to create an iort_node_map_id() function that is
> PCI agnostic (ie rename rid to id :)), whose rid_in is either a PCI RID
> or the outcome of a previous call to iort_node_get_id() for named
> components, that's in my opinion cleaner.

iort_node_map_rid() was designed for that purpose, and we can use it
for platform device, the issue that we need to pass a req id
unconditionally which is not needed for platform device, Tomasz
proposed a similar solution to rework iort_node_map_rid(), and
I think it makes sense.

> It would be even cleaner if you passed a type_mask (or write a
> wrapper function for that) that is:
>
> (IORT_MSI_TYPE | IORT_IOMMU_TYPE)

Sorry, I got little lost here, could you explain it in detail?

> and we just use the returned parent pointer to check if the mapping
> providing the initial id correspond to the type we are looking for (eg
> ITS) or we need to map the retrieved initial id any further, with
> iort_node_map_id(), to get to the final identifier.
>
> Thoughts ?

I think rework iort_node_map_rid() and not extend iort_node_get_id()
is the right direction, could you explain a bit more then I can demo
the code?

Thanks
Hanjun