linux-kernel - Re: [PATCH] USB: pci-quirks: Fix HCCPARAMS register error for LS7A EHCI

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Message-ID: <b6a18bab-b412-443a-b39a-2194596ec79d@rowland.harvard.edu>
Date: Fri, 31 Jan 2025 10:18:34 -0500
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, Baoqi Zhang <zhangbaoqi@...ngson.cn>
Subject: Re: [PATCH] USB: pci-quirks: Fix HCCPARAMS register error for LS7A
 EHCI

On Fri, Jan 31, 2025 at 06:06:51PM +0800, Huacai Chen wrote:
> LS7A EHCI controller doesn't have extended capabilities, so the EECP
> (EHCI Extended Capabilities Pointer) field of HCCPARAMS register should
> be 0x0, but it reads as 0xa0 now. This is a hardware flaw and will be
> fixed in future, now just clear the EECP field to avoid error messages
> on boot:
> 
> ......
> [    0.581675] pci 0000:00:04.1: EHCI: unrecognized capability ff
> [    0.581699] pci 0000:00:04.1: EHCI: unrecognized capability ff
> [    0.581716] pci 0000:00:04.1: EHCI: unrecognized capability ff
> [    0.581851] pci 0000:00:04.1: EHCI: unrecognized capability ff
> ......
> [    0.581916] pci 0000:00:05.1: EHCI: unrecognized capability ff
> [    0.581951] pci 0000:00:05.1: EHCI: unrecognized capability ff
> [    0.582704] pci 0000:00:05.1: EHCI: unrecognized capability ff
> [    0.582799] pci 0000:00:05.1: EHCI: unrecognized capability ff
> ......
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Baoqi Zhang <zhangbaoqi@...ngson.cn>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
>  drivers/usb/host/pci-quirks.c | 4 ++++
>  include/linux/pci_ids.h       | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 1f9c1b1435d8..7e3151400a5e 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -958,6 +958,10 @@ static void quirk_usb_disable_ehci(struct pci_dev *pdev)
>  	 * booting from USB disk or using a usb keyboard
>  	 */
>  	hcc_params = readl(base + EHCI_HCC_PARAMS);
> +	if (pdev->vendor == PCI_VENDOR_ID_LOONGSON &&
> +	    pdev->device == PCI_DEVICE_ID_LOONGSON_EHCI)
> +		hcc_params &= ~(0xffL << 8);

Can you please add a comment before this "if" statement explaining why 
it is necessary?

Alan Stern

> +
>  	offset = (hcc_params >> 8) & 0xff;
>  	while (offset && --count) {
>  		pci_read_config_dword(pdev, offset, &cap);
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index de5deb1a0118..74a84834d9eb 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -162,6 +162,7 @@
>  
>  #define PCI_VENDOR_ID_LOONGSON		0x0014
>  
> +#define PCI_DEVICE_ID_LOONGSON_EHCI     0x7a14
>  #define PCI_DEVICE_ID_LOONGSON_HDA      0x7a07
>  #define PCI_DEVICE_ID_LOONGSON_HDMI     0x7a37
>  
> -- 
> 2.47.1
>