Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device companion assignment to core code.

[Tomasz Nowicki]

On 20.01.2016 13:38, Lorenzo Pieralisi wrote:
> On Wed, Jan 20, 2016 at 12:20:07PM +0100, Tomasz Nowicki wrote:
> > On 19.01.2016 17:02, Lorenzo Pieralisi wrote:
> > > On Wed, Jan 13, 2016 at 02:20:57PM +0100, Tomasz Nowicki wrote:
> > [...]
> > > > device via pci_create_root_bus parameter (as the ACPI device type)
> > >
> > > I do not understand what you mean by "as the ACPI device type".
> >
> > See below.
> >
> > > > and using ACPI_COMPANION_SET in core code for ACPI boot method.
> > > > ACPI_COMPANION_SET is safe to run for all cases DT, ACPI and DT&ACPI.
> > > >
> > > > Suggested-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > > > Signed-off-by: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> > > > ---
> > > >   drivers/acpi/pci_root.c | 5 ++++-
> > > >   drivers/pci/probe.c     | 2 ++
> > > >   2 files changed, 6 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > > > index ae3fe4e..a65c8c2 100644
> > > > --- a/drivers/acpi/pci_root.c
> > > > +++ b/drivers/acpi/pci_root.c
> > > > @@ -846,7 +846,10 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> > > >
> > > >   	pci_acpi_root_add_resources(info);
> > > >   	pci_add_resource(&info->resources, &root->secondary);
> > > > -	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
> > > > +
> > > > +	/* Root bridge device needs to be sure of parent ACPI type */
> > > > +	ACPI_COMPANION_SET(&device->dev, device);
> > >
> > > I do not understand why the code above is needed, can you elaborate
> > > please ?
> >
> > This makes sure that device->dev can be identified as ACPI device,
> > so we can use to_acpi_device_node() and assign companion safely
> > below.
>
> I do not follow. If you refer to the fwnode handle type, that is
> already set by ACPI core code (before acpi_pci_root_add() is called,
> in acpi_init_device_object()).

acpi_init_device_object() sets ACPI fwnode handle type only for 
"device", but not for "device->dev" which is what is passed as an 
argument to pci_create_root_bus().

Without ACPI_COMPANION_SET(&device->dev, device) here, no one can be 
sure if we have ACPI device in pci_create_root_bus().

> Did you add the code above to solve a real issue you encountered ?
Yes. You can try to run series with this patch:

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 88c9d20..1b74bf6 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -967,7 +967,11 @@ struct pci_bus *acpi_pci_root_create(struct 
acpi_pci_root *root,
        pci_add_resource(&info->resources, &root->secondary);

-        /* Root bridge device needs to be sure of parent ACPI type */
-       ACPI_COMPANION_SET(&device->dev, device);
+       if (to_acpi_device_node(device->dev.fwnode) == NULL)
+               pr_err("NON-ACPI TYPE\n");
+       else
+               pr_err("ACPI TYPE\n");
+
        bus = pci_create_root_bus(&device->dev, busnum, ops->pci_ops,
                                  sysdata, &info->resources);


Thanks,
Tomasz