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SubjectRe: [PATCH v6 06/10] PCI/RCEC: Add pcie_link_rcec() to associate RCiEPs
Date
On 25 Sep 2020, at 15:15, Bjorn Helgaas wrote:

> On Tue, Sep 22, 2020 at 02:38:55PM -0700, Sean V Kelley wrote:
>> From: Sean V Kelley <sean.v.kelley@intel.com>
>>
>> A Root Complex Event Collector provides support for
>> terminating error and PME messages from associated RCiEPs.
>>
>> Make use of the RCEC Endpoint Association Extended Capability
>> to identify associated RCiEPs. Link the associated RCiEPs as
>> the RCECs are enumerated.
>>
>> Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
>> ---
>> drivers/pci/pci.h | 2 +
>> drivers/pci/pcie/portdrv_pci.c | 3 ++
>> drivers/pci/pcie/rcec.c | 96
>> ++++++++++++++++++++++++++++++++++
>> include/linux/pci.h | 1 +
>> 4 files changed, 102 insertions(+)
>>
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 7b547fc3679a..ddb5872466fb 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -474,9 +474,11 @@ static inline void pci_dpc_init(struct pci_dev
>> *pdev) {}
>> #ifdef CONFIG_PCIEPORTBUS
>> void pci_rcec_init(struct pci_dev *dev);
>> void pci_rcec_exit(struct pci_dev *dev);
>> +void pcie_link_rcec(struct pci_dev *rcec);
>> #else
>> static inline void pci_rcec_init(struct pci_dev *dev) {}
>> static inline void pci_rcec_exit(struct pci_dev *dev) {}
>> +static inline void pcie_link_rcec(struct pci_dev *rcec) {}
>> #endif
>>
>> #ifdef CONFIG_PCI_ATS
>> diff --git a/drivers/pci/pcie/portdrv_pci.c
>> b/drivers/pci/pcie/portdrv_pci.c
>> index 4d880679b9b1..dbeb0155c2c3 100644
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -110,6 +110,9 @@ static int pcie_portdrv_probe(struct pci_dev
>> *dev,
>> (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)))
>> return -ENODEV;
>>
>> + if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
>> + pcie_link_rcec(dev);
>
> Nice solution. One day we'll get rid of pcie_portdrv_probe() and
> integrate this stuff better into the PCI core, and we'll have to
> figure out a little different solution then. But we'll be smarter
> then so it should be possible :)

Indeed!

>
>> status = pcie_port_device_register(dev);
>> if (status)
>> return status;
>> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
>> index 519ae086ff41..5630480a6659 100644
>> --- a/drivers/pci/pcie/rcec.c
>> +++ b/drivers/pci/pcie/rcec.c
>> @@ -17,6 +17,102 @@
>>
>> #include "../pci.h"
>>
>> +struct walk_rcec_data {
>> + struct pci_dev *rcec;
>> + int (*user_callback)(struct pci_dev *dev, void *data);
>> + void *user_data;
>> +};
>> +
>> +static bool rcec_assoc_rciep(struct pci_dev *rcec, struct pci_dev
>> *rciep)
>> +{
>> + unsigned long bitmap = rcec->rcec_ext->bitmap;
>> + unsigned int devn;
>> +
>> + /* An RCiEP found on bus in range */
>> + if (rcec->bus->number != rciep->bus->number)
>> + return true;
>> +
>> + /* Same bus, so check bitmap */
>> + for_each_set_bit(devn, &bitmap, 32)
>> + if (devn == rciep->devfn)
>> + return true;
>> +
>> + return false;
>> +}
>> +
>> +static int link_rcec_helper(struct pci_dev *dev, void *data)
>> +{
>> + struct walk_rcec_data *rcec_data = data;
>> + struct pci_dev *rcec = rcec_data->rcec;
>> +
>> + if ((pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) &&
>> rcec_assoc_rciep(rcec, dev)) {
>> + dev->rcec = rcec;
>> + pci_dbg(dev, "PME & error events reported via %s\n",
>> pci_name(rcec));
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +void walk_rcec(int (*cb)(struct pci_dev *dev, void *data), void
>> *userdata)
>> +{
>> + struct walk_rcec_data *rcec_data = userdata;
>> + struct pci_dev *rcec = rcec_data->rcec;
>> + u8 nextbusn, lastbusn;
>> + struct pci_bus *bus;
>> + unsigned int bnr;
>> +
>> + if (!rcec->rcec_cap)
>> + return;
>> +
>> + /* Walk own bus for bitmap based association */
>> + pci_walk_bus(rcec->bus, cb, rcec_data);
>> +
>> + /* Check whether RCEC BUSN register is present */
>> + if (rcec->rcec_ext->ver < PCI_RCEC_BUSN_REG_VER)
>> + return;
>> +
>> + nextbusn = rcec->rcec_ext->nextbusn;
>> + lastbusn = rcec->rcec_ext->lastbusn;
>> +
>> + /* All RCiEP devices are on the same bus as the RCEC */
>> + if (nextbusn == 0xff && lastbusn == 0x00)
>> + return;
>> +
>> + for (bnr = nextbusn; bnr <= lastbusn; bnr++) {
>> + /* No association indicated (PCIe 5.0-1, 7.9.10.3) */
>> + if (bnr == rcec->bus->number)
>> + continue;
>> +
>> + bus = pci_find_bus(pci_domain_nr(rcec->bus), bnr);
>> + if (!bus)
>> + continue;
>> +
>> + /* Find RCiEP devices on the given bus ranges */
>> + pci_walk_bus(bus, cb, rcec_data);
>> + }
>> +}
>> +
>> +/**
>> + * pcie_link_rcec - Link RCiEP devices associating with RCEC.
>> + * @rcec RCEC whose RCiEP devices should be linked.
>> + *
>> + * Link the given RCEC to each RCiEP device found.
>> + *
>> + */
>> +void pcie_link_rcec(struct pci_dev *rcec)
>> +{
>> + struct walk_rcec_data rcec_data;
>> +
>> + if (!rcec->rcec_cap)
>> + return;
>> +
>> + rcec_data.rcec = rcec;
>> + rcec_data.user_callback = NULL;
>> + rcec_data.user_data = NULL;
>> +
>> + walk_rcec(link_rcec_helper, &rcec_data);
>> +}
>> +
>> void pci_rcec_init(struct pci_dev *dev)
>> {
>> u32 rcec, hdr, busn;
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 5c5c4eb642b6..ad382a9484ea 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -330,6 +330,7 @@ struct pci_dev {
>> #ifdef CONFIG_PCIEPORTBUS
>> u16 rcec_cap; /* RCEC capability offset */
>> struct rcec_ext *rcec_ext; /* RCEC cached assoc. endpoint extended
>> capabilities */
>> + struct pci_dev *rcec; /* Associated RCEC device */
>
> Wondering if we can put this pointer inside the struct rcec_ext (or
> whatever we call it) so we don't have to pay *two* pointers for every
> PCI device? Maybe it should be something like this:

It’s definitely unfortunate to need these two pointers. Here we have
the spec implying an association, but leaving it to software to fill in
the gaps! The spec provides a bitmap, but the reverse mapping is also
needed from the RCiEPs to the RCEC.

>
> struct rcec {
> u8 ea_ver;
> u8 ea_nextbusn;
> u8 ea_lastbusn;
> u32 ea_bitmap;
> struct pci_dev *rcec;
> }
>
> I dunno. Not sure if that would be better or worse, since we'd be
> mixing RCEC stuff (the EA capability info) with RCiEP stuff (the
> pointer to the related RCEC). Could even be a union, since any given
> device only needs one of them, but I'm pretty sure that would be
> worse.

Well, I think the pointer savings would be offset by lack of clarity on
what is going on here due to this nesting. Then again, *rcec_ea and
*rcec are not themselves revealing in terms of the relationship with
RCiEPs either. I’ll think on it some more. I do like the ea_ prefix.

>
> BTW, 03/10 didn't add a forward declaration, e.g.,
>
> struct rcec_ext;
>
> to include/linux/pci.h, and the actual definition is in
> drivers/pci/pci.h. It seems like you should need that?

Yes, it should be added. Will do.

Thanks,

Sean
>
>> #endif
>> u8 pcie_cap; /* PCIe capability offset */
>> u8 msi_cap; /* MSI capability offset */
>> --
>> 2.28.0
>>

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