Re: [PATCH V4] PCI: Add Extended Tags quirk for Broadcom HT2100 Root Port

[Ethan Zhao]

On Thu, Jul 13, 2017 at 3:34 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> On Wed, Jul 12, 2017 at 08:15:43AM -0400, Sinan Kaya wrote:
>> On 7/12/2017 5:44 AM, Ethan Zhao wrote:
>> > The dmesg yelled "...Tag handling is broken" , but didn't say how it
>> > was handled, that is weird and confusing, just because there is no
>> > device under that bridge ?
>> >
>> > How about move the messages together "...is broken, disable Extended tag..."
>
> I changed the message this:
>
>   pci 0000:00:07.0: disabling Extended Tags (this device can't handle them)
>
> We don't see any message from 0000:01:00.0 itself because it powered up
> with Extended Tags disabled.  If it powered up with Extended Tags *enabled*
> (as allowed by the ECN), we would see this:
>
>   pci 0000:00:07.0: disabling Extended Tags (this device can't handle them)
>   pci 0000:01:00.0: disabling Extended Tags
>
> Does that seem reasonable?  Complete updated patch attached below.
>
>> This was something requested by Bjorn to inform that user has a broken HW
>> when a quirk is matched.
>>
>> The new code will disable extended tags only if it was enabled on endpoint
>> via power on reset value or via some broken BIOS.
>>
>> It looks like we are not seeing any disabling message. This implies that
>> both the card and BIOS is good.
>>
>> That's why, you are no longer seeing a disabling message on this system
>> and code is just not enabling extended tags.
>
>
> commit 2e6e588b99c4c7fbcea55eb48890fa8d0ab0c3d7
> Author: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> Date:   Wed Jul 12 00:04:14 2017 -0400
>
>     PCI: Mark Broadcom HT2100 Root Port Extended Tags as broken
>
>     Per PCIe r3.1, sec 2.2.6.2 and 7.8.4, a Requester may not use 8-bit Tags
>     unless its Extended Tag Field Enable is set, but all Receivers/Completers
>     must handle 8-bit Tags correctly regardless of their Extended Tag Field
>     Enable.
>
>     Some devices do not handle 8-bit Tags as Completers, so add a quirk for
>     them.  If we find such a device, we disable Extended Tags for the entire
>     hierarchy to make peer-to-peer DMA possible.
>
>     The Broadcom HT2100 seems to have issues with handling 8-bit tags.  Mark it
>     as broken.
>
>     The pci_walk_bus() in the quirk handles devices we've enumerated in the
>     past, and pci_configure_device() handles devices we enumerate in the
>     future.
>
>     Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported")
>     Link: https://bugzilla.redhat.com/show_bug.cgi?id=1467674
>     Reported-and-tested-by: Wim ten Have <wim.ten.have@xxxxxxxxxx>
>     Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
>     [bhelgaas: changelog, tweak messages, rename bit and quirk]
>     Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 03e3d0285aea..9c3d123d358f 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -234,6 +234,7 @@ enum pci_bar_type {
>         pci_bar_mem64,          /* A 64-bit memory BAR */
>  };
>
> +int pci_configure_extended_tags(struct pci_dev *dev, void *ign);
>  bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
>                                 int crs_timeout);
>  int pci_setup_device(struct pci_dev *dev);
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index c31310db0404..c81c9835f4c7 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1745,21 +1745,50 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp)
>          */
>  }
>
> -static void pci_configure_extended_tags(struct pci_dev *dev)
> +int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
>  {
> -       u32 dev_cap;
> +       struct pci_host_bridge *host;
> +       u32 cap;
> +       u16 ctl;
>         int ret;
>
>         if (!pci_is_pcie(dev))
> -               return;
> +               return 0;
>
> -       ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &dev_cap);
> +       ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
>         if (ret)
> -               return;
> +               return 0;
> +
> +       if (!(cap & PCI_EXP_DEVCAP_EXT_TAG))
> +               return 0;
>
> -       if (dev_cap & PCI_EXP_DEVCAP_EXT_TAG)
> +       ret = pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &ctl);
> +       if (ret)
> +               return 0;
> +
> +       host = pci_find_host_bridge(dev->bus);
> +       if (!host)
> +               return 0;
> +
> +       /*
> +        * If some device in the hierarchy doesn't handle Extended Tags
> +        * correctly, make sure they're disabled.
> +        */
> +       if (host->no_ext_tags) {
> +               if (ctl & PCI_EXP_DEVCTL_EXT_TAG) {
> +                       dev_info(&dev->dev, "disabling Extended Tags\n");
> +                       pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
> +                                                  PCI_EXP_DEVCTL_EXT_TAG);
> +               }
> +               return 0;
> +       }
> +
> +       if (!(ctl & PCI_EXP_DEVCTL_EXT_TAG)) {
> +               dev_info(&dev->dev, "enabling Extended Tags\n");
>                 pcie_capability_set_word(dev, PCI_EXP_DEVCTL,
>                                          PCI_EXP_DEVCTL_EXT_TAG);
> +       }
> +       return 0;
>  }
>
>  static void pci_configure_device(struct pci_dev *dev)
> @@ -1768,7 +1797,7 @@ static void pci_configure_device(struct pci_dev *dev)
>         int ret;
>
>         pci_configure_mps(dev);
> -       pci_configure_extended_tags(dev);
> +       pci_configure_extended_tags(dev, NULL);
>
>         memset(&hpp, 0, sizeof(hpp));
>         ret = pci_get_hp_params(dev, &hpp);
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 6967c6b4cf6b..f135765555c9 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4681,3 +4681,19 @@ static void quirk_intel_no_flr(struct pci_dev *dev)
>  }
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1502, quirk_intel_no_flr);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1503, quirk_intel_no_flr);
> +
> +static void quirk_no_ext_tags(struct pci_dev *pdev)
> +{
> +       struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
> +
> +       if (!bridge)
> +               return;
> +
> +       bridge->no_ext_tags = 1;
> +       dev_info(&pdev->dev, "disabling Extended Tags (this device can't handle them)\n");

A late 'Great !', at least we get reason - (this device can't handle
them) and result - (disabling Extended Tags) at the same time, feel
better.

Thanks,
Ethan

> +
> +       pci_walk_bus(bridge->bus, pci_configure_extended_tags, NULL);
> +}
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, 0x0140, quirk_no_ext_tags);
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, 0x0142, quirk_no_ext_tags);
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, 0x0144, quirk_no_ext_tags);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 4869e66dd659..3b968d435895 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -451,6 +451,7 @@ struct pci_host_bridge {
>         void *release_data;
>         struct msi_controller *msi;
>         unsigned int ignore_reset_delay:1;      /* for entire hierarchy */
> +       unsigned int no_ext_tags:1;             /* no Extended Tags */
>         /* Resource alignment requirements */
>         resource_size_t (*align_resource)(struct pci_dev *dev,
>                         const struct resource *res,