linux-kernel - Re: [PATCH] can: xilinx: fix RX FIFO overflow error handling

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Date:	Fri, 24 Jul 2015 06:15:38 +0200
From:	Michal Simek <michal.simek@...inx.com>
To:	Andrea Scian <andrea.scian@...e.eu>, <michal.simek@...inx.com>
CC:	<mkl@...gutronix.de>, <wg@...ndegger.com>,
	<linux-can@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Kedareswara rao Appana <appana.durga.rao@...inx.com>
Subject: Re: [PATCH] can: xilinx: fix RX FIFO overflow error handling

+ Kedar

On 07/23/2015 11:13 PM, Andrea Scian wrote:
> Simply resetting the peripheral on RX FIFO overflow in not enough,
> because we also need to re-initialize the whole device.
> Also always enable RX FIFO overflow interrupt otherwise we may hang
> until another interrupt arrives (this happens if FIFO overrun and just
> read from CAN bus with candump)
> 
> Signed-off-by: Andrea Scian <andrea.scian@...e.eu>
> ---
> 
> You can reproduce the problem with the following test-bed
> * connect a Zynq based board to a PC with a CAN bus adapter (e.g. PCAN USB)
> * start sending lots of CAN messages to Zynq system
> * configure and start xilinx CAN driver
> ** canconfig can0 bitrate 1000000
> ** canconfig can0 start
> * try to send/receive messages (cansend/candump)
> * if you send a CAN message you'll get the RX FIFO error and additional messages
> will not be received
> * if you try to get messages you simple don't receive them (no interrupt triggered)
> * with canconfig stop/start the hang goes away (if the others peers stop sending
> send lots of messages ;-) )
> 
> I tested the patch over xilinx-2014.04 kernel, but the patch applies cleanly to
> mainline too.
> 
> If someone has a better understanding of Xilinx CAN driver, please let me know if
> it's better to handle the error in a different manner.
> 
> Maybe the bus off handler need the same threadment too.
> 
> TIA,
> 
> Andrea Scian
> 
> ---
>  drivers/net/can/xilinx_can.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/xilinx_can.c b/drivers/net/can/xilinx_can.c
> index 5e8b560..c278177 100644
> --- a/drivers/net/can/xilinx_can.c
> +++ b/drivers/net/can/xilinx_can.c
> @@ -100,6 +100,7 @@ enum xcan_reg {
>  #define XCAN_INTR_ALL		(XCAN_IXR_TXOK_MASK | XCAN_IXR_BSOFF_MASK |\
>  				 XCAN_IXR_WKUP_MASK | XCAN_IXR_SLP_MASK | \
>  				 XCAN_IXR_RXNEMP_MASK | XCAN_IXR_ERROR_MASK | \
> +				 XCAN_IXR_RXOFLW_MASK | \
>  				 XCAN_IXR_ARBLST_MASK | XCAN_IXR_RXOK_MASK)
>  
>  /* CAN register bit shift - XCAN_<REG>_<BIT>_SHIFT */
> @@ -526,6 +527,7 @@ static int xcan_rx(struct net_device *ndev)
>  	return 1;
>  }
>  
> +static void xcan_chip_stop(struct net_device *ndev);
>  /**
>   * xcan_err_interrupt - error frame Isr
>   * @ndev:	net_device pointer
> @@ -597,7 +599,8 @@ static void xcan_err_interrupt(struct net_device *ndev, u32 isr)
>  	if (isr & XCAN_IXR_RXOFLW_MASK) {
>  		stats->rx_over_errors++;
>  		stats->rx_errors++;
> -		priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_RESET_MASK);
> +		xcan_chip_stop(ndev);
> +		xcan_chip_start(ndev);
>  		if (skb) {
>  			cf->can_id |= CAN_ERR_CRTL;
>  			cf->data[1] |= CAN_ERR_CRTL_RX_OVERFLOW;
> 

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