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

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Message-ID: <CAAhV-H5F5zujP+=c9k7=Ce7-8+5fMS4NKuE2UqCx2SFk=g3nRA@mail.gmail.com>
Date: Sat, 1 Feb 2025 14:18:25 +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, Baoqi Zhang <zhangbaoqi@...ngson.cn>
Subject: Re: [PATCH] USB: pci-quirks: Fix HCCPARAMS register error for LS7A EHCI

Hi, Alan,

On Fri, Jan 31, 2025 at 11:18 PM Alan Stern <stern@...land.harvard.edu> wrote:
>
> 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?
OK, will do in next version.

Huacai
>
> 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
> >