Subject: [PATCH 3/3] PCI: generic: Add support for Cavium ThunderX PCIe root complexes.

From: [email-masked] (David Daney)
Date: Tue, 22 Sep 2015 09:56:52 -0700

On 09/22/2015 09:40 AM, Lorenzo Pieralisi wrote:
> On Tue, Sep 22, 2015 at 05:13:45PM +0100, David Daney wrote:
>> On 09/22/2015 09:05 AM, Lorenzo Pieralisi wrote:
>>> On Thu, Sep 17, 2015 at 11:41:34PM +0100, David Daney wrote:
>
> [...]
>
>>>>    Properties of the host controller node:
>>>>
>>>> -- compatible     : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
>>>> -                   depending on the layout of configuration space (CAM vs
>>>> -                   ECAM respectively).
>>>> +- compatible     : One of the following with bus:devfn:reg mapped to the
>>>> +                   PCI config space address window in the bit positions shown:
>>>> +                   "pci-host-cam-generic" -- 'CAM'  bits 16:8:0
>>>> +                   "pci-host-ecam-generic" -- 'ECAM'  bits 20:12:0
>>>> +                   "cavium,pci-host-thunder-pem" --  bits 24:16:0
>>>
>>> To me that's ECAM left shifted by 4. Is not it just a matter of defining
>>> config space base address (ie reg property) differently ?
>>
>> No.
>>
>> That's like saying ECAM is just CAM shifted by 4, can't we just specify
>> the "reg" differently.
>
> Ok, sorry I was not clear, apologies. I meant to ask if it is something
> that can be configured in your platform and apparently it is not,

No, the hardware cannot be adjusted.

> I worded it wrongly.

OK, I guess I also misunderstood what you were suggesting.

>
>> The "reg" property describes the base of the config space access window.
>>    CAM/ECAM/cavium,pci-host-thunder-pem describe how to generate offsets
>> from that base, The offset calculation requires information that is not
>> present in the "reg" property, it is enumerated in the various
>> "compatible" values listed above.
>
> Agreed, this also forces you to map in more virtual address space for
> a given bus, right ?

Yes.  It takes a full 32-bits of address space to have access to all PCI 
buses on the root complex.

> I am also a bit worried about how we can make this
> work with ACPI, where MCFG accessors take the bus and devfn shifts for
> granted (ie ECAM specs), so I asked.

If ACPI is not flexible enough to describe actual hardware, it will 
either have to be enhanced, or not used.

>
> Thanks,
> Lorenzo
>
>>
>> David Daney
>>
>>>
>>> Lorenzo
>>>
>>>>
>>>>    - device_type    : Must be "pci".
>>>>
>>>> diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c
>>>> index e364232..e1d8d5b 100644
>>>> --- a/drivers/pci/host/pci-host-generic.c
>>>> +++ b/drivers/pci/host/pci-host-generic.c
>>>> @@ -91,6 +91,32 @@ static struct gen_pci_cfg_bus_ops gen_pci_cfg_ecam_bus_ops = {
>>>>    	}
>>>>    };
>>>>
>>>> +static void __iomem *gen_pci_map_cfg_bus_thunder_pem(struct pci_bus *bus,
>>>> +						     unsigned int devfn,
>>>> +						     int where)
>>>> +{
>>>> +	struct gen_pci *pci = bus->sysdata;
>>>> +	resource_size_t idx = bus->number - pci->cfg.bus_range->start;
>>>> +
>>>> +	/*
>>>> +	 * Thunder PEM is a PCIe RC, but without a root bridge.  On
>>>> +	 * the primary bus, ignore accesses for devices other than
>>>> +	 * the first device.
>>>> +	 */
>>>> +	if (idx == 0 && (devfn & ~7u))
>>>> +		return NULL;
>>>> +	return pci->cfg.win[idx] + ((devfn << 16) | where);
>>>> +}
>>>> +
>>>> +static struct gen_pci_cfg_bus_ops gen_pci_cfg_thunder_pem_bus_ops = {
>>>> +	.bus_shift	= 24,
>>>> +	.ops		= {
>>>> +		.map_bus	= gen_pci_map_cfg_bus_thunder_pem,
>>>> +		.read		= pci_generic_config_read,
>>>> +		.write		= pci_generic_config_write,
>>>> +	}
>>>> +};
>>>> +
>>>>    static const struct of_device_id gen_pci_of_match[] = {
>>>>    	{ .compatible = "pci-host-cam-generic",
>>>>    	  .data = &gen_pci_cfg_cam_bus_ops },
>>>> @@ -98,6 +124,9 @@ static const struct of_device_id gen_pci_of_match[] = {
>>>>    	{ .compatible = "pci-host-ecam-generic",
>>>>    	  .data = &gen_pci_cfg_ecam_bus_ops },
>>>>
>>>> +	{ .compatible = "cavium,pci-host-thunder-pem",
>>>> +	  .data = &gen_pci_cfg_thunder_pem_bus_ops },
>>>> +
>>>>    	{ },
>>>>    };
>>>>    MODULE_DEVICE_TABLE(of, gen_pci_of_match);
>>>> --
>>>> 1.9.1
>>>>
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>>