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

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Message-ID: <56619410.4000705@cogentembedded.com>
Date:	Fri, 4 Dec 2015 16:24:32 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Chunfeng Yun <chunfeng.yun@...iatek.com>,
	Mathias Nyman <mathias.nyman@...el.com>
Cc:	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

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.

> + */
[...]

MBR, Sergei

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