Re: [PATCH V2 5/5] net: can: flexcan: fix for wrong TX error count behaviour on i.MX53

[Varka Bhadram <varkabhadram@gmail.com>]

On 07/28/2014 12:04 PM, Matthias Klein wrote:
> Once the CAN-bus is open and a packet is sent, the controller switches
> into the PASSIVE state and the TX error count goes to 0x80. When the
> bus is closed and the packet gets acknowledged the controller switches
> to ERROR-WARNING state and the TX error counter is decremented to 0x7f.
> Everything OK so far.
>
> When now the bus is open again and a packet is sent, the controller
> switches into PASSIVE state and sets the TX error count to 0x86.
> When now the bus is closed the TX error is decremented to 0x85, but
> the state does not change to ERROR-WARNING. Now with each successfully
> transfered packet (in PASSIVE state!) the TX error counter is
> decremented, and when the TX error counter reaches 0x7f the controller
> switched back into ERROR-WARNING state.
>
> This fix sets the TX error count back to zero when entering the
> ERROR-WARNING state (after the first retransfered packet is acknowledged).
>
> Signed-off-by: Matthias Klein <matthias.klein@optimeas.de>
> ---
>   drivers/net/can/flexcan.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
>
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index b77f1da..f9fefcb 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -479,6 +479,34 @@ static int flexcan_poll_bus_err(struct net_device *dev, u32 reg_esr)
>   	return 1;
>   }
>   
> +static void flexcan_reset_err_reg(struct flexcan_priv *priv)
> +{
> +	struct flexcan_regs __iomem *regs = priv->base;
> +
> +	/*
> +	 * The reset of the error counter is ugly but I don't see any other way.
> +	 * Open the CAN bus, send packet => HW goes to ERR-pasive, TX-err
> +	 * counter is around 128 (maybe 129). Close the CAN-Bus, the TX-err
> +	 * counter drops down to somewhere between 126 … 127, HW goes to
> +	 * ERR-Warning, everything is fine.
> +	 *
> +	 * Now: Repeat the above procedure. What happens is that on send the
> +	 * TX-err increases to around 134…136 and on connect it drops to
> +	 * around 130. Occording to ESR the HW is still in passive mode _but_ it
> +	 * is possible send packets - that means can send packets but has no
> +	 * clue about it.
> +	 * To get a consistent behavior here, the error counter are reset so we
> +	 * fall back to Err-Active mode and the second "can send on open bus"
> +	 * behaves just like the first one.
> +	 */
> +

networking comment style...?

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-- 
Regards,
Varka Bhadram.