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

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Date:   Thu, 14 Feb 2019 09:56:20 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     "mkl@...gutronix.de" <mkl@...gutronix.de>,
        "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>
Subject: RE: [PATCH] can: flexcan: fix timeout when set small bitrate


Kindly Ping...

Reviewed-by: Dong Aisheng <aisheng.dong@....com>

Best Regards,
Joakim Zhang

> -----Original Message-----
> From: Joakim Zhang
> Sent: 2019年1月31日 17:37
> To: mkl@...gutronix.de; linux-can@...r.kernel.org
> Cc: wg@...ndegger.com; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org; dl-linux-imx <linux-imx@....com>; Joakim
> Zhang <qiangqing.zhang@....com>
> Subject: [PATCH] can: flexcan: fix timeout when set small bitrate
> 
> Current we can meet timeout issue when setting a small bitrate like 10000 as
> follows on i.MX6UL EVK board (ipg clock = 66MHZ, per clock = 30MHZ):
> root@...6ul7d:~# 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
> 
> 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 double to FLEXCAN_TIMEOUT_US to 100 can fix the issue.
> 
> 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..1f2b4db7da88 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -166,7 +166,7 @@
>  #define FLEXCAN_MB_CNT_LENGTH(x)	(((x) & 0xf) << 16)
>  #define FLEXCAN_MB_CNT_TIMESTAMP(x)	((x) & 0xffff)
> 
> -#define FLEXCAN_TIMEOUT_US		(50)
> +#define FLEXCAN_TIMEOUT_US		(100)
> 
>  /* FLEXCAN hardware feature flags
>   *
> --
> 2.17.1