linux-kernel - Re: [PATCH] usb: xhci-mtk: fix AHB bus hang up caused by roothubs polling

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Date:	Sat, 5 Dec 2015 11:12:43 +0800
From:	chunfeng yun <chunfeng.yun@...iatek.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
CC:	Mathias Nyman <mathias.nyman@...el.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Felipe Balbi <balbi@...com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-usb@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: xhci-mtk: fix AHB bus hang up caused by roothubs
 polling

Hi,
On Fri, 2015-12-04 at 16:24 +0300, Sergei Shtylyov wrote:
> Hello.
> 
>     Sorry for the grammar nitpicking but since it's in the comments, I felt 
> the necessity to comment.
> 
> On 12/4/2015 5:40 AM, Chunfeng Yun wrote:
> 
> > when ip fail to enter sleep mode, register access protection will
> 
>     Fails.
> 
> > be disabed, at the same time if all clocks are disabled, access
>       ^^^^^^^ disabled
> 
> > register will hang up AHB bus.
> > the common case causes ip sleep fail is that after all ports enter
> 
>     Failure.
> 
> > U3 but before ip enters sleep mode, a port receives a resume
> > signal('K'). this will happens when such as clicks mouse to try to
> > do remote wakeup to stop system enter suspend.
> 
>     Wake up.
> 
> > so stop polling roothubs to avoid access xHCI register on bus
> 
>     Root hubs. Accessing.
> 
> > suspend, and restart it when bus resume.
> 
>     Resumes. Or "is resumed", maybe?
> 
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> >   drivers/usb/host/xhci-mtk.c | 23 +++++++++++++++++++++++
> >   1 file changed, 23 insertions(+)
> >
> > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> > index c9ab6a4..38635fb 100644
> > --- a/drivers/usb/host/xhci-mtk.c
> > +++ b/drivers/usb/host/xhci-mtk.c
> > @@ -696,9 +696,24 @@ static int xhci_mtk_remove(struct platform_device *dev)
> >   }
> >
> >   #ifdef CONFIG_PM_SLEEP
> > +/*
> > + * if ip sleep fail, and all clocks are disabled, access register will hang
> 
>     Fails.
> 
> > + * AHB bus, so stop poll roothubs to avoid regs access on bus suspend.
> 
>     Polling.
> 
> > + * and no need to check whether ip sleep fail or not; this will cause SPM to
> 
>     Failed.
> 
> > + * wakeup system immediately after system suspend complete if ip sleep
> 
>     Wake up.
> 
> > + * fail, it is what we wanted.
> 
>     Fails.
> 

I do need to pay more attention to the grammar from now on.

Thanks a lot

> > + */
> [...]
> 
> MBR, Sergei
> 


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