linux-kernel - Re: [PATCH] usb: host: xhci-mtk: avoid runtime suspend when removing hcd

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Message-ID: <1591189283.23525.67.camel@mtkswgap22>
Date:   Wed, 3 Jun 2020 21:01:23 +0800
From:   Macpaul Lin <macpaul.lin@...iatek.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul.lin@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-usb@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] usb: host: xhci-mtk: avoid runtime suspend when
 removing hcd

On Wed, 2020-06-03 at 14:47 +0300, Mathias Nyman wrote:
> On 29.5.2020 7.29, Macpaul Lin wrote:
> > When runtime suspend was enabled, runtime suspend might happened
> > when xhci is removing hcd. This might cause kernel panic when hcd
> > has been freed but runtime pm suspend related handle need to
> > reference it.
> > 
> > Change-Id: I70a5dc8006207caeecbac6955ce8e5345dcc70e6
> > Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
> > ---
> >  drivers/usb/host/xhci-mtk.c |    5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> > index bfbdb3c..641d24e 100644
> > --- a/drivers/usb/host/xhci-mtk.c
> > +++ b/drivers/usb/host/xhci-mtk.c
> > @@ -587,6 +587,9 @@ static int xhci_mtk_remove(struct platform_device *dev)
> >  	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
> >  	struct usb_hcd  *shared_hcd = xhci->shared_hcd;
> >  
> > +	pm_runtime_put_sync(&dev->dev);
> 
> Might runtime suspend here.
> It's a lot better than before, no panic as hcd isn't released, but a bit unnecessary.
> 
> how about this sequence instead:
> pm_runtime_disable()
> pm_runtime_put_noidle()
> 
> > +	pm_runtime_disable(&dev->dev);
> > +
> 
> -Mathias

Thanks for your suggestion!
Will it better to put no idle before disable? 
pm_runtime_put_noidle()
pm_runtime_disable()

I've found pm_runtime_put_noidle is called in pm_runtime_disable() when
there is a pending request.

I will send patch v3 as noidle() called earlier than disable(). Please
help to comment it if disable() should go before.

Thanks!
Macpaul Lin