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Date:   Wed, 16 Dec 2020 12:36:41 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Muchowski, MaciejX" <maciejx.muchowski@...el.com>,
        "Paczynski, Lukasz" <lukasz.paczynski@...el.com>
Subject: Re: [PATCH] xhci: Introduce max wait timeout in xhci_handshake()

Hi Greg,
thanks for taking a look at this.
On Tue, Dec 15, 2020 at 02:39:14PM +0100, Greg KH wrote:
> On Tue, Dec 15, 2020 at 09:22:40PM +0800, Chen Yu wrote:
> > The time to finish a xhci_handshake() is platform specific
> > and sometimes during suspend resume test the followng
> > errors were encountered:
> > [53455.418330] ACPI: Waking up from system sleep state S4
> > [66838.490856] xhci_hcd 0000:00:14.0: xHCI dying, ignoring interrupt.
> >                Shouldn't IRQs be disabled?
> > After changing the poll time granularity from 1 usec to 20 usec in
> > xhci_handshake() this issue was not reproduced. While tuning on the
> > poll time granularity might be painful on different platforms, it is
> > applicable to introduce a module parameter to allow the xhci driver to wait
> > for at max 16 ms.
> > 
> > Reported-by: "Muchowski, MaciejX" <maciejx.muchowski@...el.com>
> 
> I doubt the "X" is part of this person's name, please just spell it out
> without the "," please.
> 
Okay, will do.
> > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > ---
> >  drivers/usb/host/xhci.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index d4a8d0efbbc4..b8be9f3cc987 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -38,6 +38,10 @@ static unsigned long long quirks;
> >  module_param(quirks, ullong, S_IRUGO);
> >  MODULE_PARM_DESC(quirks, "Bit flags for quirks to be enabled as default");
> >  
> > +static int wait_handshake;
> > +module_param(wait_handshake, int, 0644);
> > +MODULE_PARM_DESC(wait_handshake, "Force wait for completion of handshake");
> 
> This is not the 1990's, we are not adding new module parameters that no
> one will know how to change.
>
Okay.
> Make this dynamic, and per-device, and work properly instead.  This can
> not handle multiple controllers in the system at all :(
>
Okay. After checking the error log, enlarging the timeout might not be enough
and I'll dig into it a little deeper and send feedback.

thanks,
Chenyu
> thanks,
> 
> greg k-h

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