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

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Date:   Wed, 11 Mar 2020 09:31:00 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Alan Cooper <alcooperx@...il.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

On 10.3.2020 20.34, Alan Cooper wrote:
> 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.
>>
>
> Agree on both points.
> Should I re-send a v2?
> 

No need, I can make those changes

-Mathias