Re: [PATCH] can: flexcan: fix timeout when set small bitrate

From: Marc Kleine-Budde
Date: Thu Jan 31 2019 - 02:34:44 EST

On 1/31/19 7:58 AM, Joakim Zhang wrote:
> From: Dong Aisheng <aisheng.dong@xxxxxxx>
>
> Current we can meet timeout issue when setting a small bitrate
> like 10000 as follows:
> root@imx6qdlsolo:~# ip link set can0 up type can bitrate 10000
> A link change request failed with some changes committed already.
> Interface can0 may have been left with an inconsistent configuration,
> please check.
> RTNETLINK answers: Connection timed out

Which SoC are you using? Which clock rate has the flexcan IP core?

> It is caused by calling of flexcan_chip_unfreeze() timeout.
>
> Originally the code is using usleep_range(10, 20) for unfreeze operation,
> but the patch (8badd65 can: flexcan: avoid calling usleep_range from
> interrupt context) changed it into udelay(10) which is only a half delay
> of before, there're also some other delay changes.
>
> After only changed unfreeze delay back to udelay(20), the issue is gone.
> So other timeout values are kept the same as 8badd65 changed.

Can you change FLEXCAN_TIMEOUT_US instead?

> Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
> ---
> drivers/net/can/flexcan.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index 2bca867bcfaa..1d3a9053bbeb 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -530,7 +530,7 @@ static int flexcan_chip_unfreeze(struct flexcan_priv *priv)
> priv->write(reg, &regs->mcr);
>
> while (timeout-- && (priv->read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
> - udelay(10);
> + udelay(20);
>
> if (priv->read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK)
> return -ETIMEDOUT;
>

Marc

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