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

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Message-ID: <ab64291d-2684-4558-8362-9195cce1de07@rowland.harvard.edu>
Date: Wed, 26 Mar 2025 10:11:48 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Huacai Chen <chenhuacai@...ngson.cn>
Cc: Huacai Chen <chenhuacai@...nel.org>,
	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 <jeffbai@...c.io>
Subject: Re: [PATCH] USB: OHCI: Add quirk for LS7A OHCI controller (rev 0x02)

On Wed, Mar 26, 2025 at 06:23:55PM +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 <jeffbai@...c.io>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
>  drivers/usb/host/ohci-pci.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/usb/host/ohci-pci.c b/drivers/usb/host/ohci-pci.c
> index 900ea0d368e0..38e535aa09fe 100644
> --- a/drivers/usb/host/ohci-pci.c
> +++ b/drivers/usb/host/ohci-pci.c
> @@ -165,6 +165,15 @@ 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);
> +
> +	hcd->regs += (pdev->revision == 0x2) ? 0x1000 : 0x0;

Please add a comment explaining why the quirk is needed and how it fixes 
the problem.

Alan Stern

> +
> +	return 0;
> +}
> +
>  static int ohci_quirk_qemu(struct usb_hcd *hcd)
>  {
>  	struct ohci_hcd *ohci = hcd_to_ohci(hcd);
> @@ -224,6 +233,10 @@ 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,
> -- 
> 2.47.1
>