linux-kernel - Re: [PATCH 2/2] usb: host: Implement workaround for Erratum A-009668

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Message-ID: <20170911120708.GE16198@kroah.com>
Date:   Mon, 11 Sep 2017 05:07:08 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     yinbo.zhu@....com
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] usb: host: Implement workaround for Erratum A-009668

On Mon, Sep 11, 2017 at 05:43:27PM +0800, yinbo.zhu@....com wrote:
> From: "yinbo.zhu" <yinbo.zhu@....com>
> 
> Description: This issue is observed in USB 2.0 mode
>  when the USB 3.0 host controller is connected to a
> FS/LS device via a hub.
> The host controller issues start-split (SSPLIT) and
> complete-split (CSPLIT) tokens to

Same comments as on patch 1/2, but also, please format the text here a
bit better.


> accomplish a split-transaction. A split-transaction
> consists of a SSPLIT token, token/data
> packets, CSPLIT token and token/data/handshake packets.
> A SSPLIT token is issued by the host controller to the
> hub followed by token/data/handshake packets. The hub
> then relays the token/data/handshake packets to the FS
> /LS device. Sometime later, the host controller issues
> a CSPLIT token followed by the same token/data/handshake
> packets to the hub to complete the split-transaction.
> As an example scenario, when the xHCI driver issues an
> Address device command with BSR=0, the host controller
> sends SETUP(SET_ADDRESS) tokens on the USB as part of
> splittransactions.
> If the host controller receives a NYET response from the
> hub for the CSPLIT SETUP token, it means that the
> split-transaction has not yet been completed or the hub
> is not able to handle the split transaction. In such a
> case, the host controller keeps retrying the
> splittransactions
> until such time an ACK response is received from the hub
> for the CSPLIT SETUP token. If the split-transactions do
> not complete in a time bound manner, the xHCI driver may
> issue a Stop Endpoint Command. The host controller does
> not service the Stop Endpoint Command and eventually the
> xHCI driver times out waiting for the Stop Endpoint Command
> to complete.
> 
> Impact: Stop Endpoint Command does not complete.
> Workaround: Instead of issuing a Stop Endpoint Command,
> issue a Disable Slot Command with the corresponding slot
> ID. Alternately, you can issue an Address Device Command
> with BSR=1.
> 
> Signed-off-by: yinbo.zhu <yinbo.zhu@....com>
> ---
>  drivers/usb/host/xhci.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 35f7821bc8b2..62d6135ad428 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -1517,6 +1517,18 @@ static int xhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
>  			urb->dev->slot_id, ep_index, 0);
>  			xhci_ring_cmd_db(xhci);
>  		}
> +
> +		/*
> +		 *A-009668: Stop Endpoint Command does not complete.
> +		 *Workaround: Instead of issuing a Stop Endpoint Command,
> +		 *issue a Disable Slot Command with the corresponding slot ID.
> +		 *Alternately, you can issue an Address Device Command with
> +		 *BSR=1
> +		 */
> +		if (urb->dev->speed <= USB_SPEED_HIGH) {
> +			xhci_queue_slot_control(xhci, command, TRB_DISABLE_SLOT,
> +						urb->dev->slot_id);
> +		}

Same comments as patch 1/2 o this part too.

thanks,

greg k-h