linux-kernel - Re: [PATCH v2] usb: dwc2: resume root hub when device detect with suspend state

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Date:	Wed, 19 Nov 2014 18:06:09 +0200
From:	Mathias Nyman <mathias.nyman@...ux.intel.com>
To:	balbi@...com, Alan Stern <stern@...land.harvard.edu>
CC:	Kever Yang <kever.yang@...k-chips.com>,
	Paul Zimmerman <paulz@...opsys.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	romain.perier@...il.com, Heiko Stuebner <heiko@...ech.de>,
	dianders@...omium.org, sonnyrao@...omium.org,
	addy.ke@...k-chips.com, cf@...k-chips.com, wulf@...k-chips.com,
	huangtao@...k-chips.com, linux-rockchip@...ts.infradead.org,
	Roy Li <roy.li@...k-chips.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: dwc2: resume root hub when device detect with
 suspend state

On 18.11.2014 18:41, Felipe Balbi wrote:
> On Tue, Nov 18, 2014 at 11:07:34AM -0500, Alan Stern wrote:
>> On Tue, 18 Nov 2014, Kever Yang wrote:
>>
>>> After we implement the bus_suspend/resume, auto suspend id enabled.
>>> The root hub will be auto suspend if there is no device connected,
>>> we need to resume the root hub when a device connect detect.
>>>
>>> This patch tested on rk3288.
>>>
>>> Signed-off-by: Roy Li <roy.li@...k-chips.com>
>>> Signed-off-by: Kever Yang <kever.yang@...k-chips.com>
>>> ---
>>>
>>> Changes in v2:
>>> - add definition for hcd structure
>>> - remove check for bus->root_hub
>>>
>>>  drivers/usb/dwc2/hcd_intr.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
>>> index 551ba87..680206f 100644
>>> --- a/drivers/usb/dwc2/hcd_intr.c
>>> +++ b/drivers/usb/dwc2/hcd_intr.c
>>> @@ -329,6 +329,7 @@ static void dwc2_port_intr(struct dwc2_hsotg *hsotg)
>>>  {
>>>  	u32 hprt0;
>>>  	u32 hprt0_modify;
>>> +	struct usb_hcd *hcd = (struct usb_hcd *)hsotg->priv;
>>>  
>>>  	dev_vdbg(hsotg->dev, "--Port Interrupt--\n");
>>>  
>>> @@ -354,6 +355,10 @@ static void dwc2_port_intr(struct dwc2_hsotg *hsotg)
>>>  		hsotg->flags.b.port_connect_status = 1;
>>>  		hprt0_modify |= HPRT0_CONNDET;
>>>  
>>> +		/* resume root hub? */
>>> +		if (hcd->state == HC_STATE_SUSPENDED)
>>> +			usb_hcd_resume_root_hub(hcd);
>>
>> You should be aware that it's not safe to use hcd->state for anything 
>> in a host controller driver.  That field is owned by usbcore, not by 
>> the HCD, and it is not protected by any locks.
>>
>> Thus, for example, hcd->state does not get set to HC_STATE_SUSPENDED
>> until some time after the bus_suspend routine has returned.  A
>> port-change interrupt might occur during that time interval.
> 
> In that case, XHCI has a bug :-) Mathias, care to add it to your TODO
> list ?
> 

I guess I'll need to check it out, thanks for pointing it out.

-Mathias
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