On Tue, 1 Feb 2022 14:18:41 -0800
Ira Weiny <ira.weiny@xxxxxxxxx> wrote:
> On Tue, Feb 01, 2022 at 10:49:47AM -0800, Widawsky, Ben wrote:
> > On 22-01-31 23:19:48, ira.weiny@xxxxxxxxx wrote:
> > > From: Ira Weiny <ira.weiny@xxxxxxxxx>
> > >
> > > Memory devices need the CDAT data from the device. This data is read
> > > from a DOE mailbox which supports the CDAT protocol.
> > >
> > > Search the DOE auxiliary devices for the one which supports the CDAT
> > > protocol. Cache that device to be used for future queries.
> > >
> > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> [snip]
>
> > >
> > > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > > index d4ae79b62a14..dcc55c4efd85 100644
> > > --- a/drivers/cxl/pci.c
> > > +++ b/drivers/cxl/pci.c
> > > @@ -536,12 +536,53 @@ static int cxl_dvsec_ranges(struct cxl_dev_state *cxlds)
> > > return rc;
> > > }
> > >
> > > +static int cxl_match_cdat_doe_device(struct device *dev, const void *data)
> > > +{
> > > + const struct cxl_dev_state *cxlds = data;
> > > + struct auxiliary_device *adev;
> > > + struct pci_doe_dev *doe_dev;
> > > +
> > > + /* First determine if this auxiliary device belongs to the cxlds */
> > > + if (cxlds->dev != dev->parent)
> > > + return 0;
> >
> > I don't understand auxiliary bus but I'm wondering why it's checking the parent
> > of the device?
>
> auxiliary_find_device() iterates all the auxiliary devices in the system. This
> check was a way for the match function to know if the auxiliary device belongs
> to the cxlds we are interested in...
>
> But now that I think about it we could have other auxiliary devices attached
> which are not DOE... :-/ So this check is not complete.
>
> FWIW I'm not thrilled with the way auxiliary_find_device() is defined. And now
> that I look at it I think the only user of it currently is wrong. They too
> have a check like this but it is after another check... :-/
>
> I was hoping to avoid having a list of DOE devices in the cxlds and simply let
> the auxiliary bus infrastructure do that somehow. IIRC Jonathan was thinking
> along the same lines. I think he actually suggested auxiliary_find_device()...
Ah.. I think I'd been thinking it was scoped to a single parent rather than
all devices in the system. Definitely rather horrible.
Can we do something with device_for_each_child() instead with a match on
bus type to check its an auxilliary bus device then I guess a name based
check on whether that is a doe. etc.
>
> It would be nice if I could have an aux_find_child() or something which
> iterated the auxiliary devices attached to a particular parent device. I've
> just not figured out exactly how to implement that better than what I did here.
>
> >
> > > +
> > > + adev = to_auxiliary_dev(dev);
> > > + doe_dev = container_of(adev, struct pci_doe_dev, adev);
> > > +
> > > + /* If it is one of ours check for the CDAT protocol */
> > > + if (pci_doe_supports_prot(doe_dev, PCI_DVSEC_VENDOR_ID_CXL,
> > > + CXL_DOE_PROTOCOL_TABLE_ACCESS))
> > > + return 1;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
> > > {
> > > struct device *dev = cxlds->dev;
> > > struct pci_dev *pdev = to_pci_dev(dev);
> > > + struct auxiliary_device *adev;
> > > + int rc;
> > >
> > > - return pci_doe_create_doe_devices(pdev);
> > > + rc = pci_doe_create_doe_devices(pdev);
> > > + if (rc)
> > > + return rc;
> > > +
> > > + adev = auxiliary_find_device(NULL, cxlds, &cxl_match_cdat_doe_device);
> > > +
> > > + if (adev) {
> > > + struct pci_doe_dev *doe_dev = container_of(adev,
> > > + struct pci_doe_dev,
> > > + adev);
> > > +
> > > + /*
> > > + * No reference need be taken. The DOE device lifetime is
> > > + * longer that the CXL device state lifetime
> > > + */
> >
> > You're holding a reference to the adev here. Did you mean to drop it?
>
> Does find device get a reference? ... Ah shoot I did not see that.
>
> Yea the reference should be dropped somewhere.
>
> Thanks,
> Ira
>
> >
> > > + cxlds->cdat_doe = doe_dev;
> > > + }
> > > +
> > > + return 0;
> > > }
> > >
> > > static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > > --
> > > 2.31.1
> > >
