On 6/19/2017 9:42 AM, Shyam Sundar S K wrote:
> on AMD platforms with SNPS 3.1 USB controller if stop endpoint command is
> issued the controller does not respond, when the EP is not in running
> state. HW completes the command execution and reports
> "Context State Error" completion code. This is as per the spec. However
> HW on receiving the second command additionally marks EP to Flow control
> state in HW which is RTL bug. This bug causes the HW not to respond
> to any further doorbells that are rung by the driver. This makes the EP
> to not functional anymore and causes gross functional failures.
>
> As a workaround, not to hit this problem, its better we check the EP state
> and issue the stop EP command only when the EP is in running state.
>
> Also, with the inclusion of this patch, there maybe a possible race
> condition that may get triggered as mentioned in the xHCI spec 4.6.9
>
> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@xxxxxxx>
> Signed-off-by: Nehal Shah <Nehal-bakulchandra.Shah@xxxxxxx>
> ---
> drivers/usb/host/xhci-hub.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 0dde49c..d39b1e0 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -398,17 +398,29 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
> spin_lock_irqsave(&xhci->lock, flags);
> for (i = LAST_EP_INDEX; i > 0; i--) {
> if (virt_dev->eps[i].ring && virt_dev->eps[i].ring->dequeue) {
> - struct xhci_command *command;
> - command = xhci_alloc_command(xhci, false, false,
> - GFP_NOWAIT);
> - if (!command) {
> - spin_unlock_irqrestore(&xhci->lock, flags);
> - xhci_free_command(xhci, cmd);
> - return -ENOMEM;
>
> + /* Check endpoint is running before stopping it,
> + * AMD SNPS 3.1 xHC may misbehave otherwise
> + */
> +
> + struct xhci_ep_ctx *ep_ctx;
> +
> + ep_ctx = xhci_get_ep_ctx(xhci, virt_dev->out_ctx, i);
> +
> + if (GET_EP_CTX_STATE(ep_ctx) == EP_STATE_RUNNING) {
> + struct xhci_command *command;
> +
> + command = xhci_alloc_command(xhci, false, false,
> + GFP_NOWAIT);
> + if (!command) {
> + spin_unlock_irqrestore(&xhci->lock,
> + flags);
> + xhci_free_command(xhci, cmd);
> + return -ENOMEM;
> + }
> + xhci_queue_stop_endpoint(xhci, command,
> + slot_id, i, suspend);
> }
> - xhci_queue_stop_endpoint(xhci, command, slot_id, i,
> - suspend);
> }
> }
> xhci_queue_stop_endpoint(xhci, cmd, slot_id, 0, suspend);
Hi Mathias,
I think, all your recommendations were taken care in the above patch. Any feedback on this ?
Thanks,
Shyam
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