Re: [PATCH v2] pci: loongson: Workaround MIPS firmware MRRS settings

[Jiaxun Yang]

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@xxxxxxxxxxx> 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@xxxxxxxxxxxxxxx
> > > 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@xxxxxxxxxxx>
> > 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);