linux-kernel - Re: [PATCH v6] usb: ohci: disable start-of-frame interrupt in ohci_rh

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Message-ID: <20211013140622.GA893308@rowland.harvard.edu>
Date:   Wed, 13 Oct 2021 10:06:22 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Yinbo Zhu <zhuyinbo@...ngson.cn>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <greg@...ah.com>,
        Patchwork Bot <patchwork-bot@...nel.org>
Subject: Re: [PATCH v6] usb: ohci: disable start-of-frame interrupt in
 ohci_rh_suspend

On Wed, Oct 13, 2021 at 11:32:08AM +0800, Yinbo Zhu wrote:
> While going into S3 or S4 suspend, an OHCI host controller can
> generate interrupt requests if the INTR_SF enable flag is set.  The
> interrupt handler routine isn't prepared for this and it doesn't turn
> off the flag, causing an interrupt storm.
> 
> To fix this problem, make ohci_rh_suspend() always disable INTR_SF
> interrupts after processing the done list and the ED unlinks but
> before the controller goes into the suspended (non-UsbOperational)
> state.  There's no reason to leave the flag enabled, since a
> suspended controller doesn't generate Start-of-Frame packets.
> 
> Signed-off-by: Yinbo Zhu <zhuyinbo@...ngson.cn>
> ---

Acked-by: Alan Stern <stern@...land.harvard.edu>

> Change in v6:
> 		1. Rework the commit log information.
> 		2. Move the key change code after ohci_work in 
> 		   ohci_rh_suspend.
> 
> 
>  drivers/usb/host/ohci-hub.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/host/ohci-hub.c b/drivers/usb/host/ohci-hub.c
> index f474f2f..90cee19 100644
> --- a/drivers/usb/host/ohci-hub.c
> +++ b/drivers/usb/host/ohci-hub.c
> @@ -91,6 +91,9 @@ static int ohci_rh_suspend (struct ohci_hcd *ohci, int autostop)
>  	update_done_list(ohci);
>  	ohci_work(ohci);
>  
> +	/* All ED unlinks should be finished, no need for SOF interrupts */
> +	ohci_writel(ohci, OHCI_INTR_SF, &ohci->regs->intrdisable);
> +
>  	/*
>  	 * Some controllers don't handle "global" suspend properly if
>  	 * there are unsuspended ports.  For these controllers, put all
> -- 
> 1.8.3.1
>