linux-kernel - Re: [PATCH V2] USB: OHCI: Add quirk for LS7A OHCI controller (rev 0x02)

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Message-ID: <CAAhV-H4aitynD20EEWQhF_uv79+1nw7sKxzd7c_+009oY63tEg@mail.gmail.com>
Date: Sat, 29 Mar 2025 16:40:59 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Huacai Chen <chenhuacai@...ngson.cn>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Mingcong Bai <baimingcong@...ngson.cn>
Subject: Re: [PATCH V2] USB: OHCI: Add quirk for LS7A OHCI controller (rev 0x02)

On Thu, Mar 27, 2025 at 10:13 PM Alan Stern <stern@...land.harvard.edu> wrote:
>
> On Thu, Mar 27, 2025 at 12:48:40PM +0800, Huacai Chen wrote:
> > The OHCI controller (rev 0x02) under LS7A PCI host has a hardware flaw.
> > MMIO register with offset 0x60/0x64 is treated as legacy PS2-compatible
> > keyboard/mouse interface, which confuse the OHCI controller. Since OHCI
> > only use a 4KB BAR resource indeed, the LS7A OHCI controller's 32KB BAR
> > is wrapped around (the second 4KB BAR space is the same as the first 4KB
> > internally). So we can add an 4KB offset (0x1000) to the OHCI registers
> > (from the PCI BAR resource) as a quirk.
> >
> > Cc: stable@...r.kernel.org
> > Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > Tested-by: Mingcong Bai <baimingcong@...ngson.cn>
> > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > ---
> > V2: add a comment explaining why the quirk is needed and how it fixes.
> >
> >  drivers/usb/host/ohci-pci.c | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/usb/host/ohci-pci.c b/drivers/usb/host/ohci-pci.c
> > index 900ea0d368e0..bd90b2fed51b 100644
> > --- a/drivers/usb/host/ohci-pci.c
> > +++ b/drivers/usb/host/ohci-pci.c
> > @@ -165,6 +165,24 @@ static int ohci_quirk_amd700(struct usb_hcd *hcd)
> >       return 0;
> >  }
> >
> > +static int ohci_quirk_loongson(struct usb_hcd *hcd)
> > +{
> > +     struct pci_dev *pdev = to_pci_dev(hcd->self.controller);
> > +
> > +     /*
> > +      * Loongson's LS7A OHCI controller (rev 0x02) has a
> > +      * flaw. MMIO register with offset 0x60/64 is treated
> > +      * as legacy PS2-compatible keyboard/mouse interface.
> > +      * Since OHCI only use 4KB BAR resource, LS7A OHCI's
> > +      * 32KB BAR is wrapped around (the 2nd 4KB BAR space
> > +      * is the same as the 1st 4KB internally). So add 4KB
> > +      * offset (0x1000) to the OHCI registers as a quirk.
> > +      */
> > +     hcd->regs += (pdev->revision == 0x2) ? 0x1000 : 0x0;
>
> I'm sorry, I should have mentioned this previously but I only noticed it
> now.  This would be a lot easier for people to read if you wrote it as a
> simple "if" statement:
>
>         if (pdev->revision == 0x02)
>                 hcd->regs += 0x1000;
>
> Otherwise the patch looks fine.  If you make this change, you can
> resubmit it with:
>
> Reviewed-by: Alan Stern <stern@...land.harvard.edu>
Thanks, V3 is sent:
https://lore.kernel.org/linux-usb/20250328040059.3672979-1-chenhuacai@loongson.cn/T/#u

Huacai

>
> Alan Stern
>
> > +
> > +     return 0;
> > +}
> > +
> >  static int ohci_quirk_qemu(struct usb_hcd *hcd)
> >  {
> >       struct ohci_hcd *ohci = hcd_to_ohci(hcd);
> > @@ -224,6 +242,10 @@ static const struct pci_device_id ohci_pci_quirks[] = {
> >               PCI_DEVICE(PCI_VENDOR_ID_ATI, 0x4399),
> >               .driver_data = (unsigned long)ohci_quirk_amd700,
> >       },
> > +     {
> > +             PCI_DEVICE(PCI_VENDOR_ID_LOONGSON, 0x7a24),
> > +             .driver_data = (unsigned long)ohci_quirk_loongson,
> > +     },
> >       {
> >               .vendor         = PCI_VENDOR_ID_APPLE,
> >               .device         = 0x003f,