linux-kernel - Re: [PATCH 4/5] usb: call pm_runtime_put_sync in pm_runtime_get

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Date:	Thu, 28 Feb 2013 16:37:21 +0800
From:	Lan Tianyu <tianyu.lan@...el.com>
To:	Li Fei <fei.li@...el.com>, stern@...land.harvard.edu
CC:	gregkh@...uxfoundation.org, sarah.a.sharp@...ux.intel.com,
	rjw@...k.pl, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, chuansheng.liu@...el.com
Subject: Re: [PATCH 4/5] usb: call pm_runtime_put_sync in pm_runtime_get_sync
 failed case

On 2013年02月28日 15:57, Li Fei wrote:
> 
> Even in failed case of pm_runtime_get_sync, the usage_count
> is incremented. In order to keep the usage_count with correct
> value and runtime power management to behave correctly, call
> pm_runtime_put(_sync) in such case.

Hi Fei:
	It's not necessary. Because the did_runtime_put == true means the
port's usage count has already been decreased during
usb_port_suspend().So to keep usage count balance, we should increase
the usage count in the usb_port_resume() whatever.
	
> 
> Signed-off-by Liu Chuansheng <chuansheng.liu@...el.com>
> Signed-off-by: Li Fei <fei.li@...el.com>
> ---
>  drivers/usb/core/hub.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 5480352..b68493b 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3152,6 +3152,7 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>  		if (status < 0) {
>  			dev_dbg(&udev->dev, "can't resume usb port, status %d\n",
>  					status);
> +			pm_runtime_put_sync(&port_dev->dev);
>  			return status;
>  		}
>  	}
> 
Hi Alan:
	Further thinking, the device should be disconnected since the port
can't be resumed and the device will not work normally. Something like
following. Does this make sense?
---
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index d5d3de4..cf36b11 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3170,6 +3170,7 @@ int usb_port_resume(struct usb_device *udev,
pm_message_t msg)
                if (status < 0) {
                        dev_dbg(&udev->dev, "can't resume usb port,
status %d\n",
                                        status);
+                       hub_port_logical_disconnect(hub, port1);
                        return status;
                }
        }


-- 
Best regards
Tianyu Lan
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