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

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Date:   Thu, 31 Jan 2019 08:34:24 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Joakim Zhang <qiangqing.zhang@....com>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
Cc:     "wg@...ndegger.com" <wg@...ndegger.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Aisheng Dong <aisheng.dong@....com>
Subject: Re: [PATCH] can: flexcan: fix timeout when set small bitrate

On 1/31/19 7:58 AM, Joakim Zhang wrote:
> From: Dong Aisheng <aisheng.dong@....com>
> 
> Current we can meet timeout issue when setting a small bitrate
> like 10000 as follows:
> root@...6qdlsolo:~# 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@....com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
>  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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