RE: [PATCH V6 1/2] PCI/ACPI: Provide acpi_get_rc_resources() for ARM64 platform

[Gabriele Paoloni <gabriele.paoloni@huawei.com>]

Hi Lorenzo

Thanks for reviewing

> -----Original Message-----
> From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi@arm.com]
> Sent: 22 November 2016 15:57
> To: liudongdong (C)
> Cc: helgaas@kernel.org; arnd@arndb.de; rafael@kernel.org;
> tn@semihalf.com; Wangzhou (B); pratyush.anand@gmail.com; linux-
> pci@vger.kernel.org; linux-acpi@vger.kernel.org; linux-
> kernel@vger.kernel.org; jcm@redhat.com; Gabriele Paoloni; Chenxin
> (Charles); hanjun.guo@linaro.org; Linuxarm
> Subject: Re: [PATCH V6 1/2] PCI/ACPI: Provide acpi_get_rc_resources()
> for ARM64 platform
> 
> On Tue, Nov 22, 2016 at 08:08:48PM +0800, Dongdong Liu wrote:
> > The acpi_get_rc_resources() is used to get the RC register address
> that can
> > not be described in MCFG. It takes the _HID&segment to look for and
> returns
> > the RC address resource. Use PNP0C02 devices to describe such RC
> address
> > resource. Use _UID to match segment to tell which root bus the
> PNP0C02
> > resource belong to.
> 
> Here (ie interpreting the _UID as a segment identifier) is where we
> start interpreting the specs instead of relying on them, if you want to
> go ahead with this feel free but I do not like this attitude at all.

Obviously there are no specs to specify the segment id of a quirk.
Looking at the ACPI specs it seems to me that the _UID is no worse
than other device identification objects...

Maybe we can use the _SUN as an alternative solution?

> 
> > Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
> > Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> > ---
> >  drivers/pci/pci-acpi.c | 69
> ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/pci/pci.h      |  4 +++
> >  2 files changed, 73 insertions(+)
> >
> > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> > index d966d47..76fd6f4 100644
> > --- a/drivers/pci/pci-acpi.c
> > +++ b/drivers/pci/pci-acpi.c
> > @@ -29,6 +29,75 @@
> >  	0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
> >  };
> >
> > +#ifdef CONFIG_ARM64
> 
> CONFIG_PCI_ECAM_QUIRKS (that you will introduce earlier in your
> series).
> 
> The way you did it seems to imply that on ARM64 to get RC address we
> need to (and are allowed to) use this function (and related, *Linux
> specific*, ACPI bindings) and that's a generic way of getting config
> space. It is not and it must not be and I consider it a bit of a
> stretch
> to have it in generic code but I can live with that as long as it comes
> with its own config option that describes that this stuff is
> non-compliant code used by non-compliant platform drivers.

Yes probably better to have

#ifdef CONFIG_PCI_ECAM_QUIRKS

Thanks

Gab

> 
> Thanks,
> Lorenzo
> 
> > +static struct resource *acpi_get_rc_addr(struct acpi_device *adev)
> > +{
> > +	struct resource_entry *entry;
> > +	struct list_head list;
> > +	unsigned long flags;
> > +	int ret;
> > +	struct resource *res;
> > +
> > +	INIT_LIST_HEAD(&list);
> > +	flags = IORESOURCE_MEM;
> > +	ret = acpi_dev_get_resources(adev, &list,
> > +				     acpi_dev_filter_resource_type_cb,
> > +				     (void *) flags);
> > +	if (ret <= 0)
> > +		return NULL;
> > +
> > +	entry = list_first_entry(&list, struct resource_entry, node);
> > +	res = entry->res;
> > +	acpi_dev_free_resource_list(&list);
> > +	return res;
> > +}
> > +
> > +static acpi_status acpi_match_rc(acpi_handle handle, u32 lvl, void
> *context,
> > +				 void **retval)
> > +{
> > +	u16 *segment = context;
> > +	unsigned long long uid;
> > +	acpi_status status;
> > +
> > +	status = acpi_evaluate_integer(handle, "_UID", NULL, &uid);
> > +	if (ACPI_FAILURE(status) || uid != *segment)
> > +		return AE_CTRL_DEPTH;
> > +
> > +	*(acpi_handle *)retval = handle;
> > +	return AE_CTRL_TERMINATE;
> > +}
> > +
> > +/**
> > + * acpi_get_rc_resources() - get the RC address resource.
> > + * @hid:	HID to search for.
> > + * @segment:	PCI Segment number.
> > + *
> > + * Get the RC address resource that can not be described in MCFG. It
> takes
> > + * the _HID&segment to look for and returns the RC address resource.
> Use
> > + * _CRS of PNP0C02 devices to describe such RC address resource. Use
> _UID
> > + * to match segment to tell which root bus the PNP0C02 resource
> belong to.
> > + *
> > + * Return: RC address resource.
> > + */
> > +struct resource *acpi_get_rc_resources(const char *hid, u16 segment)
> > +{
> > +	struct acpi_device *adev;
> > +	acpi_status status;
> > +	acpi_handle handle;
> > +	int ret;
> > +
> > +	status = acpi_get_devices(hid, acpi_match_rc, &segment, &handle);
> > +	if (ACPI_FAILURE(status))
> > +		return -ENODEV;
> > +
> > +	ret = acpi_bus_get_device(handle, &adev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return acpi_get_rc_addr(adev);
> > +}
> > +#endif
> > +
> >  phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
> >  {
> >  	acpi_status status = AE_NOT_EXIST;
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 4518562..bf1dbfe 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -356,4 +356,8 @@ static inline int pci_dev_specific_reset(struct
> pci_dev *dev, int probe)
> >  }
> >  #endif
> >
> > +#if defined(CONFIG_ARM64) && defined(CONFIG_ACPI)
> > +struct resource *acpi_get_rc_resources(const char *hid, u16
> segment);
> > +#endif
> > +
> >  #endif /* DRIVERS_PCI_H */
> > --
> > 1.9.1
> >