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    SubjectRe: [PATCH v2] pci: loongson: Workaround MIPS firmware MRRS settings
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    在 2023/8/29 20:26, Linux regression tracking (Thorsten Leemhuis) 写道:
    > Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
    > for once, to make this easily accessible to everyone.
    >
    > What's the status here? From my point it looks like this regression that
    > was ported six weeks ago is still not fixed -- and it seems nothing has
    > happened since three weeks now. But maybe I'm just missing something,
    > that's why I'm asking.

    Hi Thorsten,

    Thanks for reaching back, unfortunately there is no progress so far.

    + Huacai, what's your opinion here? I do think this fix is in best shape for
    now.

    Thanks
    - Jiaxun

    >
    > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
    > --
    > Everything you wanna know about Linux kernel regression tracking:
    > https://linux-regtracking.leemhuis.info/about/#tldr
    > If I did something stupid, please tell me, as explained on that page.
    >
    > #regzbot poke
    >
    > On 08.08.23 09:38, Jiaxun Yang wrote:
    >>
    >> 在 2023/8/6 22:30, Huacai Chen 写道:
    >>> Hi, Jiaxun,
    >>>
    >>> On Sun, Aug 6, 2023 at 10:20 AM Jiaxun Yang <jiaxun.yang@flygoat.com>
    >>> wrote:
    >>>>
    >>>> 在 2023/7/25 14:10, Jiaxun Yang 写道:
    >>>>> This is a partial revert of commit 8b3517f88ff2 ("PCI:
    >>>>> loongson: Prevent LS7A MRRS increases") for MIPS based Loongson.
    >>>>>
    >>>>> There are many MIPS based Loongson systems in wild that
    >>>>> shipped with firmware which does not set maximum MRRS properly.
    >>>>>
    >>>>> Limiting MRRS to 256 for all as MIPS Loongson comes with higher
    >>>>> MRRS support is considered rare.
    >>>>>
    >>>>> Cc: stable@vger.kernel.org
    >>>>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217680
    >>>>> Fixes: 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS increases")
    >>>>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
    >>>> Ping?
    >>>> I expect this patch to go through PCI fixes tree.
    >>> Can we do it like this by modifying the existing loongson_mrrs_quirk()?
    >> Hmm, I'm not sure this will work, since loongson_mrrs_quirk only run on
    >> bridges
    >> but the old quirk should run on every single device.
    >>
    >> Thanks
    >> Jiaxun
    >>
    >>> static void loongson_mrrs_quirk(struct pci_dev *pdev)
    >>> {
    >>>          /*
    >>>           * Some Loongson PCIe ports have h/w limitations of maximum read
    >>>           * request size. They can't handle anything larger than this. So
    >>>           * force this limit on any devices attached under these ports.
    >>>           */
    >>>          struct pci_host_bridge *bridge =
    >>> pci_find_host_bridge(pdev->bus);
    >>>
    >>> #ifdef CONFIG_MIPS
    >>>          set_pcie_ports_to_mrrs_256_to_emulate_the_firmware_behavior();
    >>> #endif
    >>>
    >>>          bridge->no_inc_mrrs = 1;
    >>> }
    >>>
    >>>> Thanks
    >>>> - Jiaxun
    >>>>
    >>>>> ---
    >>>>> v2: Rename quirk name to: loongson_old_mrrs_quirk
    >>>>> ---
    >>>>>    drivers/pci/controller/pci-loongson.c | 38
    >>>>> +++++++++++++++++++++++++++
    >>>>>    1 file changed, 38 insertions(+)
    >>>>>
    >>>>> diff --git a/drivers/pci/controller/pci-loongson.c
    >>>>> b/drivers/pci/controller/pci-loongson.c
    >>>>> index fe0f732f6e43..d0f68b102d10 100644
    >>>>> --- a/drivers/pci/controller/pci-loongson.c
    >>>>> +++ b/drivers/pci/controller/pci-loongson.c
    >>>>> @@ -108,6 +108,44 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
    >>>>>    DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
    >>>>>                        DEV_LS7A_PCIE_PORT6, loongson_mrrs_quirk);
    >>>>>
    >>>>> +#ifdef CONFIG_MIPS
    >>>>> +static void loongson_old_mrrs_quirk(struct pci_dev *pdev)
    >>>>> +{
    >>>>> +     struct pci_bus *bus = pdev->bus;
    >>>>> +     struct pci_dev *bridge;
    >>>>> +     static const struct pci_device_id bridge_devids[] = {
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS2K_PCIE_PORT0) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT0) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT1) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT2) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT3) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT4) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT5) },
    >>>>> +             { PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT6) },
    >>>>> +             { 0, },
    >>>>> +     };
    >>>>> +
    >>>>> +     /* look for the matching bridge */
    >>>>> +     while (!pci_is_root_bus(bus)) {
    >>>>> +             bridge = bus->self;
    >>>>> +             bus = bus->parent;
    >>>>> +             /*
    >>>>> +              * There are still some wild MIPS Loongson firmware won't
    >>>>> +              * set MRRS properly. Limiting MRRS to 256 as MIPS
    >>>>> Loongson
    >>>>> +              * comes with higher MRRS support is considered rare.
    >>>>> +              */
    >>>>> +             if (pci_match_id(bridge_devids, bridge)) {
    >>>>> +                     if (pcie_get_readrq(pdev) > 256) {
    >>>>> +                             pci_info(pdev, "limiting MRRS to 256\n");
    >>>>> +                             pcie_set_readrq(pdev, 256);
    >>>>> +                     }
    >>>>> +                     break;
    >>>>> +             }
    >>>>> +     }
    >>>>> +}
    >>>>> +DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID,
    >>>>> loongson_old_mrrs_quirk);
    >>>>> +#endif
    >>>>> +
    >>>>>    static void loongson_pci_pin_quirk(struct pci_dev *pdev)
    >>>>>    {
    >>>>>        pdev->pin = 1 + (PCI_FUNC(pdev->devfn) & 3);

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