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Date:   Fri, 17 May 2019 19:18:43 +0200
From:   Marc Kleine-Budde <>
To:     Joakim Zhang <>,
        "" <>
Cc:     dl-linux-imx <>,
        "" <>,
        "" <>,
        Aisheng Dong <>
Subject: Re: [PATCH] can: flexcan: fix deadlock when using self wakeup

On 5/17/19 4:39 AM, Joakim Zhang wrote:
> As reproted by Sean Nyekjaer bellow:
> 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.
> Fixes: de3578c198c6 ("can: flexcan: add self wakeup support")
> This patch intends to fix the issue, and also add comment to explain the
> wakeup flow.
> Signed-off-by: Joakim Zhang <>

The existing self wakeup support:

| de3578c198c6 ("can: flexcan: add self wakeup support")

looks broken to me.

According to the data sheet:

> To enter stop mode, the CPU should manually assert a global Stop Mode
> request (see the CAN1_STOP_REQ and CAN2_STOP_REQ bit in the register
> IOMUXC_GPR4) and check the acknowledgement asserted by the FlexCAN
> (see the CAN1_STOP_ACK and CAN2_STOP_ACK in the register
> IOMUXC_GPR4). The CPU must only consider the FlexCAN in Stop Mode
> when both request and acknowledgement conditions are satisfied.
you have to poll for the acknowledgement, which is not done in the
driver. Please fix that first.

As far as I understand the documentation the suspend() and resume
functions should be symmetric. If they are, you shouldn't need the
in_stop_mode hack.


Pengutronix e.K.                  | Marc Kleine-Budde           |
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