Re: [PATCH v25 01/33] xhci: add helper to stop endpoint and wait for completion

[Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>]

On 8/23/24 22:00, Wesley Cheng wrote:
> From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
> 
> Expose xhci_stop_endpoint_sync() which is a synchronous variant of
> xhci_queue_stop_endpoint().  This is useful for client drivers that are
> using the secondary interrupters, and need to stop/clean up the current
> session.  The stop endpoint command handler will also take care of cleaning
> up the ring.
> 
> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
> Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
> ---
>  drivers/usb/host/xhci.c | 39 +++++++++++++++++++++++++++++++++++++++
>  drivers/usb/host/xhci.h |  2 ++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 37eb37b0affa..3a051ed32907 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -2784,6 +2784,45 @@ static int xhci_reserve_bandwidth(struct xhci_hcd *xhci,
>  	return -ENOMEM;
>  }
>  
> +/*
> + * Synchronous XHCI stop endpoint helper.  Issues the stop endpoint command and
> + * waits for the command completion before returning.
> + */
> +int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep, int suspend,
> +			    gfp_t gfp_flags)
> +{
> +	struct xhci_command *command;
> +	unsigned long flags;
> +	int ret;
> +
> +	command = xhci_alloc_command(xhci, true, gfp_flags);
> +	if (!command)
> +		return -ENOMEM;
> +
> +	spin_lock_irqsave(&xhci->lock, flags);
> +	ret = xhci_queue_stop_endpoint(xhci, command, ep->vdev->slot_id,
> +				       ep->ep_index, suspend);
> +	if (ret < 0) {
> +		spin_unlock_irqrestore(&xhci->lock, flags);
> +		goto out;
> +	}
> +
> +	xhci_ring_cmd_db(xhci);
> +	spin_unlock_irqrestore(&xhci->lock, flags);
> +
> +	wait_for_completion(command->completion);
> +
> +	if (command->status == COMP_COMMAND_ABORTED ||
> +	    command->status == COMP_COMMAND_RING_STOPPED) {
> +		xhci_warn(xhci, "Timeout while waiting for stop endpoint command\n");

nit-pick: is this really a timeout? In that case you would have used
wait_for_completion_timeout(), no?

> +		ret = -ETIME;
> +	}
> +out:
> +	xhci_free_command(xhci, command);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(xhci_stop_endpoint_sync);
>  
>  /* Issue a configure endpoint command or evaluate context command
>   * and wait for it to finish.
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 30415158ed3c..1c6126ed55b0 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1914,6 +1914,8 @@ void xhci_ring_doorbell_for_active_rings(struct xhci_hcd *xhci,
>  void xhci_cleanup_command_queue(struct xhci_hcd *xhci);
>  void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring);
>  unsigned int count_trbs(u64 addr, u64 len);
> +int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
> +			    int suspend, gfp_t gfp_flags);
>  
>  /* xHCI roothub code */
>  void xhci_set_link_state(struct xhci_hcd *xhci, struct xhci_port *port,