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

[Alan Stern]

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@xxxxxxxxxxxxxxx
> Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Tested-by: Mingcong Bai <baimingcong@xxxxxxxxxxx>
> Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxxxxxxxx>

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,