Re: [PATCH v2 1/3] can: cc770: Remove redundant IRQ ack

[Richard Weinberger <richard@sigma-star.at>]

Andri,

Am Dienstag, 30. Januar 2018, 17:56:47 CET schrieb Andri Yngvason:
> This has been reported to cause stalls on rt-linux.
> 
> Signed-off-by: Andri Yngvason <andri.yngvason@marel.com>
> ---
>  drivers/net/can/cc770/cc770.c | 15 ---------------
>  1 file changed, 15 deletions(-)
> 
> diff --git a/drivers/net/can/cc770/cc770.c b/drivers/net/can/cc770/cc770.c
> index 1e37313..9fed163 100644
> --- a/drivers/net/can/cc770/cc770.c
> +++ b/drivers/net/can/cc770/cc770.c
> @@ -447,15 +447,6 @@ static netdev_tx_t cc770_start_xmit(struct sk_buff
> *skb, struct net_device *dev)
> 
>  	stats->tx_bytes += dlc;
> 
> -
> -	/*
> -	 * HM: We had some cases of repeated IRQs so make sure the
> -	 * INT is acknowledged I know it's already further up, but
> -	 * doing again fixed the issue
> -	 */
> -	cc770_write_reg(priv, msgobj[mo].ctrl0,
> -			MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES);
> -
>  	return NETDEV_TX_OK;
>  }
> 
> @@ -684,12 +675,6 @@ static void cc770_tx_interrupt(struct net_device *dev,
> unsigned int o) /* Nothing more to send, switch off interrupts */
>  	cc770_write_reg(priv, msgobj[mo].ctrl0,
>  			MSGVAL_RES | TXIE_RES | RXIE_RES | INTPND_RES);
> -	/*
> -	 * We had some cases of repeated IRQ so make sure the
> -	 * INT is acknowledged
> -	 */
> -	cc770_write_reg(priv, msgobj[mo].ctrl0,
> -			MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES);
> 
>  	stats->tx_packets++;
>  	can_get_echo_skb(dev, 0);

I saw that stalls too.
But instead of just removing these writes I suggest adding a quirk for the can 
card where they cause trouble.
Maybe Wolfgang can give more details why they are here.

Thanks,
//richard

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