linux-kernel - Re: [PATCH V6 1/2] PCI/ACPI: Provide acpi_get_rc

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Date:   Tue, 22 Nov 2016 15:56:48 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Dongdong Liu <liudongdong3@...wei.com>
Cc:     helgaas@...nel.org, arnd@...db.de, rafael@...nel.org,
        tn@...ihalf.com, wangzhou1@...ilicon.com, pratyush.anand@...il.com,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, jcm@...hat.com,
        gabriele.paoloni@...wei.com, charles.chenxin@...wei.com,
        hanjun.guo@...aro.org, linuxarm@...wei.com
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.

> Signed-off-by: Dongdong Liu <liudongdong3@...wei.com>
> Signed-off-by: Tomasz Nowicki <tn@...ihalf.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.

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
>