netdev - RE: [PATCH 1/3] can: flexcan: fix deadlock when using self wakeup

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Date:   Fri, 15 Nov 2019 09:20:58 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Sean Nyekjaer <sean@...nix.com>,
        "mkl@...gutronix.de" <mkl@...gutronix.de>
CC:     "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 1/3] can: flexcan: fix deadlock when using self wakeup


> -----Original Message-----
> From: linux-can-owner@...r.kernel.org <linux-can-owner@...r.kernel.org>
> On Behalf Of Sean Nyekjaer
> Sent: 2019年11月15日 17:08
> To: Joakim Zhang <qiangqing.zhang@....com>; mkl@...gutronix.de
> Cc: linux-can@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> netdev@...r.kernel.org
> Subject: Re: [PATCH 1/3] can: flexcan: fix deadlock when using self wakeup
> 
> 
> 
> On 15/11/2019 06.03, Joakim Zhang wrote:
> > From: Sean Nyekjaer <sean@...nix.com>
> >
> > When suspending, when there is still can traffic on the interfaces the
> > flexcan immediately wakes the platform again. As it should :-). But it
> > throws this error msg:
> > [ 3169.378661] PM: noirq suspend of devices failed
> >
> > On the way down to suspend the interface that throws the error message
> > does call flexcan_suspend but fails to call flexcan_noirq_suspend.
> > That means the flexcan_enter_stop_mode is called, but on the way out
> > of suspend the driver only calls flexcan_resume and skips
> > flexcan_noirq_resume, thus it doesn't call flexcan_exit_stop_mode.
> > This leaves the flexcan in stop mode, and with the current driver it
> > can't recover from this even with a soft reboot, it requires a hard reboot.
> >
> > This patch can fix deadlock when using self wakeup, it happenes to be
> > able to fix another issue that frames out-of-order in first IRQ
> > handler run after wakeup.
> >
> > In wakeup case, after system resume, frames received out-of-order,the
> > problem is wakeup latency from frame reception to IRQ handler is much
> > bigger than the counter overflow. This means it's impossible to sort
> > the CAN frames by timestamp. The reason is that controller exits stop
> > mode during noirq resume, then it can receive the frame immediately.
> > If noirq reusme stage consumes much time, it will extend interrupt
> > response time.
> >
> > Fixes: de3578c198c6 ("can: flexcan: add self wakeup support")
> > Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> 
> Hi Joakim and Marc
> 
> We have quite a few devices in the field where flexcan is stuck in Stop-Mode.
> We do not have the possibility to cold reboot them, and hot reboot will not get
> flexcan out of stop-mode.
> So flexcan comes up with:
> [  279.444077] flexcan: probe of 2090000.flexcan failed with error -110
> [  279.501405] flexcan: probe of 2094000.flexcan failed with error -110
> 
> They are on, de3578c198c6 ("can: flexcan: add self wakeup support")
> 
> Would it be a solution to add a check in the probe function to pull it out of
> stop-mode?

Hi Sean,

I am not sure, I will try to implement it.

Best Regards,
Joakim Zhang
> /Sean