RE: [PATCH v1 3/7] fpga: dfl: Allow for ports with no local bar space.

Zhang, Tianfei
2022-02-21T07:48:48Z

> -----Original Message-----
> From: Wu, Hao <hao.wu@intel.com>
> Sent: Wednesday, February 16, 2022 11:38 AM
> To: Zhang, Tianfei <tianfei.zhang@intel.com>; trix@redhat.com;
> mdf@kernel.org; Xu, Yilun <yilun.xu@intel.com>; linux-fpga@vger.kernel.org;
> linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: corbet@lwn.net; Matthew Gerlach <matthew.gerlach@linux.intel.com>
> Subject: Re: [PATCH v1 3/7] fpga: dfl: Allow for ports with no local bar space.
>
> > Subject: [PATCH v1 3/7] fpga: dfl: Allow for ports with no local bar space.
> >
> > From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> >
> > From a fpga partial reconfiguration standpoint, a port may not be
> > connected any local BAR space. The port could be connected to a
> > different PCIe Physical Function (PF) or Virtual Function (VF), in
> > which case another driver instance would manage the endpoint.
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> > Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
> > ---
> > drivers/fpga/dfl-pci.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c index
> > 4d68719e608f..8abd9b408403 100644
> > --- a/drivers/fpga/dfl-pci.c
> > +++ b/drivers/fpga/dfl-pci.c
> > @@ -243,6 +243,7 @@ static int find_dfls_by_default(struct pci_dev *pcidev,
> > v = readq(base + FME_HDR_CAP);
> > port_num = FIELD_GET(FME_CAP_NUM_PORTS, v);
> >
> > + dev_info(&pcidev->dev, "port_num = %d\n", port_num);
>
> Do we really need this info here? in FME there is one sysfs interface for port
> num.

I think it is not necessary, I will remove it.

>
> > WARN_ON(port_num > MAX_DFL_FPGA_PORT_NUM);
> >
> > for (i = 0; i < port_num; i++) {
> > @@ -258,6 +259,13 @@ static int find_dfls_by_default(struct pci_dev *pcidev,
> > */
> > bar = FIELD_GET(FME_PORT_OFST_BAR_ID, v);
> > offset = FIELD_GET(FME_PORT_OFST_DFH_OFST, v);
> > + if (bar >= PCI_STD_NUM_BARS) {
> > + dev_info(&pcidev->dev, "skipping port without
> > local BAR space %d\n",
> > + bar);
> > + continue;
>
> Is this change for IOFS? From patch #1, we have FME and PORT on PF0, so we
> should have a BAR for PORT on PF0, is my understanding correct?

Yes, we have a Port device on each PR slot in IOFS, but for " Multiple VFs per PR slot" model,
the Port device would not connected to AFU/PR slot (the BarID of Port device should be set to invalid),
and we just can access PR slot/AFU resource via VFs.

>
> Thanks
> Hao
>
> > + } else {
> > + dev_info(&pcidev->dev, "BAR %d offset %u\n",
> > bar, offset);
> > + }
> > start = pci_resource_start(pcidev, bar) + offset;
> > len = pci_resource_len(pcidev, bar) - offset;
> >
> > --
> > 2.17.1