linux-kernel - Re: [PATCH v2] usb/host/ehci-hub: Fix the issue EG20T USB host controller has long resuming time, when pen drive is attached.

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Date:	Thu, 12 Jul 2012 10:44:07 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Tomoya MORINAGA <tomoya.rohm@...il.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb/host/ehci-hub: Fix the issue EG20T USB host
 controller has long resuming time, when pen drive is attached.

On Thu, 12 Jul 2012, Tomoya MORINAGA wrote:

> Intel EG20T USB host controller does not send SOF in resuming time
> after suspending, if the FLR bit was not cleared. When pen drive is
> attached, the controller has a long resuming time to try re-connect
> it. This patch clear the FLR bit in suspending time for fixing the
> issue.
> 
> Signed-off-by: Tomoya MORINAGA <tomoya.rohm@...il.com>
> ---
> v2: Update comments from Alan Stern
> 	Add patch description
> 	Always clear the STS_FLR flag.
> ---
>  drivers/usb/host/ehci-hub.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
> index fc9e7cc..818a2f1 100644
> --- a/drivers/usb/host/ehci-hub.c
> +++ b/drivers/usb/host/ehci-hub.c
> @@ -318,6 +318,7 @@ static int ehci_bus_suspend (struct usb_hcd *hcd)
>  	ehci_readl(ehci, &ehci->regs->intr_enable);
>  
>  	ehci->next_statechange = jiffies + msecs_to_jiffies(10);
> +	ehci_writel(ehci, STS_FLR, &ehci->regs->status);
>  	spin_unlock_irq (&ehci->lock);

You need to add a comment to the code also.  Otherwise, a few years
from now somebody will see that line, realize it doesn't do anything
important, and get rid of it.

Alan Stern

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