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Date: Wed, 05 Aug 2020 11:07:36 -0700
From: "Sean V Kelley" <sean.v.kelley@...el.com>
To: "Bjorn Helgaas" <helgaas@...nel.org>
Cc: bhelgaas@...gle.com, Jonathan.Cameron@...wei.com,
rjw@...ysocki.net, ashok.raj@...el.com, tony.luck@...el.com,
sathyanarayanan.kuppuswamy@...ux.intel.com,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
"Qiuxu Zhuo" <qiuxu.zhuo@...el.com>
Subject: Re: [PATCH V2 3/9] PCI/portdrv: Add pcie_walk_rcec() to walk RCiEPs
associated with RCEC
On 5 Aug 2020, at 10:43, Bjorn Helgaas wrote:
> On Tue, Aug 04, 2020 at 12:40:46PM -0700, Sean V Kelley wrote:
>> From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>>
>> When an RCEC device signals error(s) to a CPU core, the CPU core
>> needs to walk all the RCiEPs associated with that RCEC to check
>> errors. So add the function pcie_walk_rcec() to walk all RCiEPs
>> associated with the RCEC device.
>>
>> Co-developed-by: Sean V Kelley <sean.v.kelley@...el.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>> ---
>> drivers/pci/pcie/portdrv.h | 2 +
>> drivers/pci/pcie/portdrv_core.c | 82
>> +++++++++++++++++++++++++++++++++
>> 2 files changed, 84 insertions(+)
>>
>> diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
>> index af7cf237432a..c11d5ecbad76 100644
>> --- a/drivers/pci/pcie/portdrv.h
>> +++ b/drivers/pci/pcie/portdrv.h
>> @@ -116,6 +116,8 @@ void pcie_port_service_unregister(struct
>> pcie_port_service_driver *new);
>>
>> extern struct bus_type pcie_port_bus_type;
>> int pcie_port_device_register(struct pci_dev *dev);
>> +void pcie_walk_rcec(struct pci_dev *rcec, int (*cb)(struct pci_dev
>> *, void *),
>> + void *userdata);
>> #ifdef CONFIG_PM
>> int pcie_port_device_suspend(struct device *dev);
>> int pcie_port_device_resume_noirq(struct device *dev);
>> diff --git a/drivers/pci/pcie/portdrv_core.c
>> b/drivers/pci/pcie/portdrv_core.c
>> index 5d4a400094fc..daa2dfa83a0b 100644
>> --- a/drivers/pci/pcie/portdrv_core.c
>> +++ b/drivers/pci/pcie/portdrv_core.c
>> @@ -14,6 +14,7 @@
>> #include <linux/pm_runtime.h>
>> #include <linux/string.h>
>> #include <linux/slab.h>
>> +#include <linux/bitops.h>
>> #include <linux/aer.h>
>>
>> #include "../pci.h"
>> @@ -365,6 +366,87 @@ int pcie_port_device_register(struct pci_dev
>> *dev)
>> return status;
>> }
>>
>> +static int pcie_walk_rciep_devfn(struct pci_bus *pbus, int
>> (*cb)(struct pci_dev *, void *),
>
> In drivers/pci, the typical name for a "struct pci_bus *" is "bus",
> and for a "struct pci_dev *" is "dev" (below).
>
>> + void *userdata, unsigned long bitmap)
Will correct.
>
> Use "u32 bitmap" so the width is explicit. Looks like this would also
> get rid of the cast in the caller. So maybe you used "unsigned long"
> here for some reason?
Will correct. Somehow one cast led to another. Should have been u32.
>
>> +{
>> + unsigned int dev, fn;
>> + struct pci_dev *pdev;
>> + int retval;
>> +
>> + for_each_set_bit(dev, &bitmap, 32) {
>> + for (fn = 0; fn < 8; fn++) {
>> + pdev = pci_get_slot(pbus, PCI_DEVFN(dev, fn));
>
> This needs a matching pci_dev_put(), according to the pci_get_slot()
> function comment.
Will add.
>
>> +
>> + if (!pdev || pci_pcie_type(pdev) != PCI_EXP_TYPE_RC_END)
>> + continue;
>> +
>> + retval = cb(pdev, userdata);
>> + if (retval)
>> + return retval;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * pcie_walk_rcec - Walk RCiEP devices associating with RCEC and
>> call callback.
>> + * @rcec RCEC whose RCiEP devices should be walked.
>> + * @cb Callback to be called for each RCiEP device found.
>> + * @userdata Arbitrary pointer to be passed to callback.
>> + *
>> + * Walk the given RCEC. Call the provided callback on each RCiEP
>> device found.
>> + *
>> + * We check the return of @cb each time. If it returns anything
>> + * other than 0, we break out.
>> + */
>> +void pcie_walk_rcec(struct pci_dev *rcec, int (*cb)(struct pci_dev
>> *, void *),
>> + void *userdata)
>> +{
>> + u32 pos, bitmap, hdr, busn;
>> + u8 ver, nextbusn, lastbusn;
>> + struct pci_bus *pbus;
>> + unsigned int bnr;
>> +
>> + pos = pci_find_ext_capability(rcec, PCI_EXT_CAP_ID_RCEC);
>> + if (!pos)
>> + return;
>
> I think all the registers you care about here are read-only. If so,
> we
> should find the capability, read the registers (bitmap & bus numbers),
> and save them at enumeration-time, e.g., in pci_init_capabilities().
> I hope we don't have to dig all this out every time we process an
> error.
I originally went that way by caching the rcec cap (pos) in pci_dev on
probe. Will make changes to cache at enumeration time.
>
>> + pbus = pci_find_bus(pci_domain_nr(rcec->bus), rcec->bus->number);
>> + if (!pbus)
>> + return;
>
> This seems like a really complicated way to write:
>
> pbus = rcec->bus;
>
> "rcec->bus" cannot be NULL, so there's no need to check.
For some reason, at the time it appeared I needed to call pci_find_bus.
But that makes sense if it is always valid. Will correct.
>
>> + pci_read_config_dword(rcec, pos + PCI_RCEC_RCIEP_BITMAP, &bitmap);
>> +
>> + /* Find RCiEP devices on the same bus as the RCEC */
>> + if (pcie_walk_rciep_devfn(pbus, cb, userdata, (unsigned
>> long)bitmap))
>> + return;
>> +
>> + /* Check whether RCEC BUSN register is present */
>> + pci_read_config_dword(rcec, pos, &hdr);
>> + ver = PCI_EXT_CAP_VER(hdr);
>> + if (ver < PCI_RCEC_BUSN_REG_VER)
>> + return;
>> +
>> + pci_read_config_dword(rcec, pos + PCI_RCEC_BUSN, &busn);
>> + nextbusn = PCI_RCEC_BUSN_NEXT(busn);
>> + lastbusn = PCI_RCEC_BUSN_LAST(busn);
>> +
>> + /* All RCiEP devices are on the same bus as the RCEC */
>> + if (nextbusn == 0xff && lastbusn == 0x00)
>> + return;
>> +
>> + for (bnr = nextbusn; bnr <= lastbusn; bnr++) {
>> + pbus = pci_find_bus(pci_domain_nr(rcec->bus), bnr);
>> + if (!pbus)
>> + continue;
>> +
>> + /* Find RCiEP devices on the given bus */
>> + if (pcie_walk_rciep_devfn(pbus, cb, userdata, 0xffffffff))
>> + return;
>> + }
>> +}
>> +
>> #ifdef CONFIG_PM
>> typedef int (*pcie_pm_callback_t)(struct pcie_device *);
>>
>> --
>> 2.27.0
>>
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