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Date:   Thu, 28 Sep 2023 16:31:52 +0300
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To:     Wesley Cheng <quic_wcheng@quicinc.com>, mathias.nyman@intel.com,
        gregkh@linuxfoundation.org, lgirdwood@gmail.com,
        broonie@kernel.org, perex@perex.cz, tiwai@suse.com,
        agross@kernel.org, andersson@kernel.org, konrad.dybcio@linaro.org,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, srinivas.kandagatla@linaro.org,
        bgoswami@quicinc.com, Thinh.Nguyen@synopsys.com
Cc:     linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        alsa-devel@alsa-project.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org
References: <20230921214843.18450-1-quic_wcheng@quicinc.com>
 <20230921214843.18450-3-quic_wcheng@quicinc.com>
From:   Mathias Nyman <mathias.nyman@linux.intel.com>
Subject: Re: [PATCH v7 02/33] xhci: add helper to stop endpoint and wait for
 completion
In-Reply-To: <20230921214843.18450-3-quic_wcheng@quicinc.com>
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On 22.9.2023 0.48, Wesley Cheng wrote:
> From: Mathias Nyman <mathias.nyman@linux.intel.com>
> 
> 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.
> 
> Modifications to repurpose the new API into existing stop endpoint
> sequences was implemented by Wesley Cheng.
> 
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> Co-developed-by: Wesley Cheng <quic_wcheng@quicinc.com>
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>   drivers/usb/host/xhci-hub.c | 29 +++---------------
>   drivers/usb/host/xhci.c     | 60 +++++++++++++++++++++++++++----------
>   drivers/usb/host/xhci.h     |  2 ++
>   3 files changed, 50 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 0054d02239e2..2f7309bdc922 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -489,7 +489,6 @@ EXPORT_SYMBOL_GPL(xhci_find_slot_id_by_port);
>   static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>   {
>   	struct xhci_virt_device *virt_dev;
> -	struct xhci_command *cmd;
>   	unsigned long flags;
>   	int ret;
>   	int i;
> @@ -501,10 +500,6 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>   
>   	trace_xhci_stop_device(virt_dev);
>   
> -	cmd = xhci_alloc_command(xhci, true, GFP_NOIO);
> -	if (!cmd)
> -		return -ENOMEM;
> -
>   	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) {
> @@ -521,7 +516,7 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>   			if (!command) {
>   				spin_unlock_irqrestore(&xhci->lock, flags);
>   				ret = -ENOMEM;
> -				goto cmd_cleanup;
> +				goto out;
>   			}
>   
>   			ret = xhci_queue_stop_endpoint(xhci, command, slot_id,
> @@ -529,30 +524,14 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>   			if (ret) {
>   				spin_unlock_irqrestore(&xhci->lock, flags);
>   				xhci_free_command(xhci, command);
> -				goto cmd_cleanup;
> +				goto out;
>   			}
>   		}
>   	}
> -	ret = xhci_queue_stop_endpoint(xhci, cmd, slot_id, 0, suspend);
> -	if (ret) {
> -		spin_unlock_irqrestore(&xhci->lock, flags);
> -		goto cmd_cleanup;
> -	}
> -
> -	xhci_ring_cmd_db(xhci);
>   	spin_unlock_irqrestore(&xhci->lock, flags);
> +	ret = xhci_stop_endpoint_sync(xhci, &virt_dev->eps[0], suspend);

I didn't take this new xhci_stop_endpoint_sync() helper into use as it causes an extra
xhci spinlock release and reacquire here.

Also the memory allocation flags differ, GFP_NOIO is turned into GFP_KERNEL after this change.

>   
> -	/* Wait for last stop endpoint command to finish */
> -	wait_for_completion(cmd->completion);
> -
> -	if (cmd->status == COMP_COMMAND_ABORTED ||
> -	    cmd->status == COMP_COMMAND_RING_STOPPED) {
> -		xhci_warn(xhci, "Timeout while waiting for stop endpoint command\n");
> -		ret = -ETIME;
> -	}
> -
> -cmd_cleanup:
> -	xhci_free_command(xhci, cmd);
> +out:
>   	return ret;
>   }
>   
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 3fd2b58ee1d3..163d533d6200 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -2758,6 +2758,46 @@ 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)
> +{
> +	struct xhci_command *command;
> +	unsigned long flags;
> +	int ret;
> +
> +	command = xhci_alloc_command(xhci, true, GFP_KERNEL);
> +	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);
> +
> +	ret = wait_for_completion_timeout(command->completion, msecs_to_jiffies(3000));
> +	if (!ret)
> +		xhci_warn(xhci, "%s: Unable to stop endpoint.\n",
> +				__func__);
> +
> +	if (command->status == COMP_COMMAND_ABORTED ||
> +	    command->status == COMP_COMMAND_RING_STOPPED) {
> +		xhci_warn(xhci, "Timeout while waiting for stop endpoint command\n");
> +		ret = -ETIME;
> +	}
> +out:
> +	xhci_free_command(xhci, command);
> +
> +	return ret;
> +}
>   
>   /* Issue a configure endpoint command or evaluate context command
>    * and wait for it to finish.
> @@ -3078,7 +3118,7 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd,
>   	struct xhci_virt_device *vdev;
>   	struct xhci_virt_ep *ep;
>   	struct xhci_input_control_ctx *ctrl_ctx;
> -	struct xhci_command *stop_cmd, *cfg_cmd;
> +	struct xhci_command *cfg_cmd;
>   	unsigned int ep_index;
>   	unsigned long flags;
>   	u32 ep_flag;
> @@ -3118,10 +3158,6 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd,
>   	if (ep_flag == SLOT_FLAG || ep_flag == EP0_FLAG)
>   		return;
>   
> -	stop_cmd = xhci_alloc_command(xhci, true, GFP_NOWAIT);
> -	if (!stop_cmd)
> -		return;
> -
>   	cfg_cmd = xhci_alloc_command_with_ctx(xhci, true, GFP_NOWAIT);
>   	if (!cfg_cmd)
>   		goto cleanup;
> @@ -3144,23 +3180,16 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd,
>   		goto cleanup;
>   	}
>   
> -	err = xhci_queue_stop_endpoint(xhci, stop_cmd, udev->slot_id,
> -					ep_index, 0);
> +	spin_unlock_irqrestore(&xhci->lock, flags);
> +

Same here, extra unlock -> lock, and GFP flags differ.


> +	err = xhci_stop_endpoint_sync(xhci, ep, 0);

Thanks
Mathias