linux-kernel - Re: [PATCH] usb: xhci: Error enumerating USB TV Tuner

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Message-ID: <CAOGqxeWhsdtvmZBg3RLzSyHeLpCWGoRghTp+8u3gx3Aafi-vgA@mail.gmail.com>
Date:   Tue, 10 Mar 2020 14:34:58 -0400
From:   Alan Cooper <alcooperx@...il.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     ": Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...el.com>
Subject: Re: [PATCH] usb: xhci: Error enumerating USB TV Tuner

Agree on both points.
Should I re-send a v2?

Thanks
Al

On Mon, Mar 9, 2020 at 8:19 AM Mathias Nyman
<mathias.nyman@...ux.intel.com> wrote:
>
> On 6.3.2020 18.06, Al Cooper wrote:
> > Unable to complete the enumeration of a USB TV Tuner device.
> >
> > Per XHCI spec (4.6.5), the EP state field of the input context shall
> > be cleared for a set address command. In the special case of an FS
> > device that has "MaxPacketSize0 = 8", the Linux XHCI driver does
> > not do this before evaluating the context. With an XHCI controller
> > that checks the EP state field for parameter context error this
> > causes a problem in cases such as the device getting reset again
> > after enumeration.
> >
> > When that field is cleared, the problem does not occur.
> >
> > This was found and fixed by Sasi Kumar.
> >
> > Signed-off-by: Al Cooper <alcooperx@...il.com>
> > ---
> >  drivers/usb/host/xhci.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index dbac0fa9748d..5f034e143082 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -1428,6 +1428,7 @@ static int xhci_check_maxpacket(struct xhci_hcd *xhci, unsigned int slot_id,
> >                               xhci->devs[slot_id]->out_ctx, ep_index);
> >
> >               ep_ctx = xhci_get_ep_ctx(xhci, command->in_ctx, ep_index);
> > +             ep_ctx->ep_info &= cpu_to_le32(~EP_STATE_MASK);/* must clear */
> >               ep_ctx->ep_info2 &= cpu_to_le32(~MAX_PACKET_MASK);
> >               ep_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(max_packet_size));
> >
> >
>
> Thanks, nice catch.
>
> If you agree I'd like to change the the subject of this patch to something like:
> "xhci: Fix enumeration issue when setting actual max packet size for FS devices"
>
> While looking at this it seems that the current EP_STATE_MASK is not correct either.
> It should be 0x7 instead of 0xf.
>
> -Mathias