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

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

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,
I worded it wrongly.

> 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 ? 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.

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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> >>
>