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

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Date:	Tue, 18 Nov 2014 11:07:34 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Kever Yang <kever.yang@...k-chips.com>
cc:	Paul Zimmerman <paulz@...opsys.com>, Felipe Balbi <balbi@...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 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.

Alan Stern

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