netdev - RE: [PATCH V2 2/4] can: flexcan: try to exit stop mode during probe stage

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Date:   Thu, 5 Dec 2019 11:04:53 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Sean Nyekjaer <sean@...nix.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC:     dl-linux-imx <linux-imx@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH V2 2/4] can: flexcan: try to exit stop mode during probe
 stage


> -----Original Message-----
> From: Sean Nyekjaer <sean@...nix.com>
> Sent: 2019年12月5日 17:22
> To: Marc Kleine-Budde <mkl@...gutronix.de>; Joakim Zhang
> <qiangqing.zhang@....com>; linux-can@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>; netdev@...r.kernel.org
> Subject: Re: [PATCH V2 2/4] can: flexcan: try to exit stop mode during probe
> stage
> 
> 
> 
> On 04/12/2019 09.45, Marc Kleine-Budde wrote:
> > On 12/4/19 3:22 AM, Joakim Zhang wrote:
> >>
> >>> -----Original Message-----
> >>> From: Marc Kleine-Budde <mkl@...gutronix.de>
> >>> Sent: 2019年12月4日 2:15
> >>> To: Joakim Zhang <qiangqing.zhang@....com>; sean@...nix.com;
> >>> linux-can@...r.kernel.org
> >>> Cc: dl-linux-imx <linux-imx@....com>; netdev@...r.kernel.org
> >>> Subject: Re: [PATCH V2 2/4] can: flexcan: try to exit stop mode
> >>> during probe stage
> >>>
> >>> On 11/27/19 6:56 AM, Joakim Zhang wrote:
> >>>> CAN controller could be stucked in stop mode once it enters stop
> >>>> mode
> >>>                            ^^^^^^^ stuck
> >>>> when suspend, and then it fails to exit stop mode when resume.
> >>>
> >>> How can this happen?
> >>
> >> I am also confused how can this happen, as I asked Sean, only CAN
> >> enter stop mode when suspend, then system hang,
> > How do you recover the system when suspended?
> >
> >> it could let CAN
> >> stuck in stop mode. However, Sean said this indeed happen at his
> >> side, @sean@...nix.com, could you explain how this happen in details?
> > That would be good.
> >
> >>>> Only code reset can get CAN out of stop mode,
> >>>
> >>> What is "code reset"?
> >>
> >> As I know, "code reset" is to press the POWER KEY from the board. At
> >> my side, reboot command from OS also can get CAN out of stop mode.
> > Do you mean "cold reset", also known as Power-On-Reset, POR or power
> cycle?
> >
> > What does pressing the POWER KEY do? A power cycle of the system or
> > toggling the reset line of the imx?
> >
> > We need to describe in detail, as not everyone has the same board as
> > you, and these boards might not even have a power key :)
> >
> >> Below is experiment I did:
> >> 	Firstly, do a hacking to let CAN stuck into stop mode, then:
> >
> > You mean you put the CAN into stop mode without keeping track in the
> > CAN driver that the CAN-IP is in stop mode, e.g. by hacking the driver.
> >
> > Then you try several methods to recover:
> >
> >> 	(1) press power on/off key, get CAN out of stop mode;
> >> 	(2) reboot command from console, get CAN out of stop mode;
> >> 	(3) unbind/bind driver, cannot get CAN out of stop mode;
> >> 	(4) remod/insmod module, cannot get CAN out of stop mode;
> >
> > (2) resets the complete imx, including the CAN-IP core, (1) probably, too.
> No, if the CAN-IP core is in stop-mode it will stay that way even after a reboot
> from the console.
> At least it's what we are seeing in the field.
> 
> This could be because we are missing a wire from the watchdog out to the
> RESETBMCU/PWRON on the PMIC.
> But i guess a check for if the CAN-Ip is in stop-mode doesn't hurt anything :)
Hi Sean,

At my side, both Power-On-Reset and reboot from console can get CAN-IP out of stop mode, HW is i.MX7D-SDB/i.MX8QXP-mek.
I think HW design could make difference.

We more care about how does CAN-IP stuck in stop mode, could you please explain in details? We want figure out the root cause.

> /Sean