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

[Jiaxun Yang]

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@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);