Re: [RFC PATCH 2/9] PCI: Extend Root Port Driver to support RCEC

[Sean V Kelley]

On 27 Jul 2020, at 5:30, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:16 -0700
> Sean V Kelley <sean.v.kelley@xxxxxxxxx> wrote:
>
> > From: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
> >
> > If a Root Complex Integrated Endpoint (RCiEP) is implemented, errors 
> > may
> > optionally be sent to a corresponding Root Complex Event Collector 
> > (RCEC).
> > Each RCiEP must be associated with no more than one RCEC. Interface 
> > errors
> > are reported to the OS by RCECs.
> >
> > For an RCEC (technically not a Bridge), error messages "received" 
> > from
> > associated RCiEPs must be enabled for "transmission" in order to 
> > cause a
> > System Error via the Root Control register or (when the Advanced 
> > Error
> > Reporting Capability is present) reporting via the Root Error Command
> > register and logging in the Root Error Status register and Error 
> > Source
> > Identification register.
> >
> > Given the commonality with Root Ports and the need to also support 
> > AER
> > and PME services for RCECs, extend the Root Port driver to support 
> > RCEC
> > devices through the addition of the RCEC Class ID to the driver
> > structure.
> Hi.
>
> I'm surprised it ended up this simple :) Seems we are a bit lucky that
> the existing code is rather flexible on what is there and what isn't
> and that there is never any reason to directly touch the various
> type1 specific registers (given as I read the spec, an RCEC uses a
> type0 config space header unlike the ports).

Which is part of the reason why I chose to refer to it as an RFC, 
because it seemed simpler and I was unsure if we were missing anything, 
and it turns out we were. Unfortunately, to avoid churn, Iâve left 
quite a bit of comments/naming intact with ârootâ/âportâ terms.

> Given you mention PME, it's probably worth noting (I think) you aren't
> actually enabling the service yet as there is a check in that path on 
> whether we
> have a root port or not.
> https://elixir.bootlin.com/linux/v5.8-rc4/source/drivers/pci/pcie/portdrv_core.c#L241

Good catch, testing has been only done at this point with AER injection.
Will correct.

Thanks,

Sean

> Thanks,
>
> Jonathan
>
>
> > Co-developed-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
> > Signed-off-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > ---
> >  drivers/pci/pcie/portdrv_pci.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/pcie/portdrv_pci.c 
> > b/drivers/pci/pcie/portdrv_pci.c
> > index 3acf151ae015..d5b109499b10 100644
> > --- a/drivers/pci/pcie/portdrv_pci.c
> > +++ b/drivers/pci/pcie/portdrv_pci.c
> > @@ -106,7 +106,8 @@ static int pcie_portdrv_probe(struct pci_dev 
> > *dev,
> >  	if (!pci_is_pcie(dev) ||
> >  	    ((pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT) &&
> >  	     (pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM) &&
> > -	     (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM)))
> > +	     (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM) &&
> > +	     (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)))
> >  		return -ENODEV;
> >
> >  	status = pcie_port_device_register(dev);
> > @@ -195,6 +196,8 @@ static const struct pci_device_id port_pci_ids[] 
> > = {
> >  	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0) },
> >  	/* subtractive decode PCI-to-PCI bridge, class type is 060401h */
> >  	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x01), ~0) },
> > +	/* handle any Root Complex Event Collector */
> > +	{ PCI_DEVICE_CLASS(((PCI_CLASS_SYSTEM_RCEC << 8) | 0x00), ~0) },
> >  	{ },
> >  };