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

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Date:   Wed, 4 Dec 2019 02:22:29 +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


> -----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, 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?

> > 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.
Below is experiment I did:
	Firstly, do a hacking to let CAN stuck into stop mode, then:
	(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;

> > 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.

Best Regards,
Joakim Zhang
> > MCR[LPMACK] will be checked when enable CAN in register_flexcandev().
> >
> > Suggested-by: Sean Nyekjaer <sean@...nix.com>
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>

[...]

> Marc
> 
> --
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
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