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

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Message-ID: <DB7PR04MB46186FB41B5873FED5ABEC06E65C0@DB7PR04MB4618.eurprd04.prod.outlook.com>
Date:   Thu, 5 Dec 2019 08:46:58 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "sean@...nix.com" <sean@...nix.com>,
        "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


Hi Sean,

Could you please answer Marc's concern in details when you are free? Then we can discuss how to fix it more reasonable. Thanks.
 
Best Regards,
Joakim Zhang

> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: 2019年12月4日 16:45
> 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 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.
> 
> (3) and (4) fail to recover the CAN core, as the IP core is still powered off by
> some upstream component. So the question why this happens in the first place
> is IMHO as important as trying to wake up the core. I think if we discover this
> situation (CAN Core is in stop-mode in probe) we should print a warning
> message, but try to recover.
> 
> >>> so add stop mode remove request during probe stage for other
> >>> methods(soft reset from chip level, unbind/bind driver, etc) to let
> >>         ^^^ please add a space
> >>> CAN active again.
> >>
> >> Can you rephrase the sentence after "so add stop mode remove request
> >> during probe stage". I'm not completely sure what you want to tell.
> >
> > Sure.
> 
> tnx,
> Marc
> 
> --
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
> Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |