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

From: [email-masked] (David Daney)
Date: Tue, 22 Sep 2015 09:13:45 -0700

On 09/22/2015 09:05 AM, Lorenzo Pieralisi wrote:
> On Thu, Sep 17, 2015 at 11:41:34PM +0100, David Daney wrote:
>> From: David Daney <[email-masked]>
>>
>> The config space for external PCIe root complexes on some Cavium
>> ThunderX SoCs is very similar to CAM and ECAM, but differs in the
>> shift values that have to be applied to the bus and devfn numbers to
>> compose that address window offset.  These root complexes also have
>> the interesting property that there is no root bridge, so the standard
>> manner of limiting scanning to only the first device doesn't work.  We
>> can use the standard pci-host-generic driver if we make a minor
>> addition to handle these differences, so we...
>>
>> Add a mapping function for ThunderX PCIe root complexes with a bus
>> shift of 24 and devfn shift of 16.  Ignore accesses for devices other
>> than the first device on the primary bus.
>>
>> Document the whole thing in devicetree/bindings/pci/host-generic-pci.txt
>>
>> Signed-off-by: David Daney <[email-masked]>
>> ---
>>   .../devicetree/bindings/pci/host-generic-pci.txt   |  8 +++---
>>   drivers/pci/host/pci-host-generic.c                | 29 ++++++++++++++++++++++
>>   2 files changed, 34 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.txt b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
>> index 105a968..a5aed0f 100644
>> --- a/Documentation/devicetree/bindings/pci/host-generic-pci.txt
>> +++ b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
>> @@ -14,9 +14,11 @@ tree bindings communicated in pci.txt:
>>
>>   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.

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.

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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