linux-kernel - Re: [PATCH net-next-2.6 v8 01/20] CAN : Add flow control processing.

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Date:	Sun, 12 Dec 2010 16:26:06 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Tomoya MORINAGA <tomoya-linux@....okisemi.com>
CC:	Wolfgang Grandegger <wg@...ndegger.com>,
	socketcan-core@...ts.berlios.de, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, andrew.chih.howe.khor@...el.com,
	qi.wang@...el.com, margie.foster@...el.com, yong.y.wang@...el.com,
	kok.howg.ewe@...el.com, joel.clark@...el.com
Subject: Re: [PATCH net-next-2.6 v8 01/20] CAN : Add flow control processing.

On 12/07/2010 12:00 PM, Tomoya MORINAGA wrote:
> Currently, there is no flow control processing.
> Thus, Add flow control processing as
> when there is no empty of tx buffer,
> netif_stop_queue is called.
> When there is empty buffer, netif_wake_queue is called.

See comment inline.

> Signed-off-by: Tomoya MORINAGA <tomoya-linux@....okisemi.com>
> ---
>  drivers/net/can/pch_can.c |   31 ++++++++++++-------------------
>  1 files changed, 12 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/net/can/pch_can.c b/drivers/net/can/pch_can.c
> index a9b6a65..f0f1404 100644
> --- a/drivers/net/can/pch_can.c
> +++ b/drivers/net/can/pch_can.c
> @@ -102,6 +102,10 @@
>  
>  #define PCH_FIFO_THRESH		16
>  
> +/* TxRqst2 show status of MsgObjNo.17~32 */
> +#define PCH_TREQ2_TX_MASK	(((1 << PCH_TX_OBJ_NUM) - 1) <<\
> +							(PCH_RX_OBJ_END - 16))
> +
>  enum pch_ifreg {
>  	PCH_RX_IFREG,
>  	PCH_TX_IFREG,
> @@ -871,6 +875,8 @@ MSG_OBJ:
>  			dlc = 8;
>  		stats->tx_bytes += dlc;
>  		stats->tx_packets++;
> +		if (int_stat == PCH_TX_OBJ_END)
> +			netif_wake_queue(ndev);
>  	}
>  
>  	int_stat = pch_can_int_pending(priv);
> @@ -1009,18 +1015,6 @@ static int pch_close(struct net_device *ndev)
>  	return 0;
>  }
>  
> -static int pch_get_msg_obj_sts(struct net_device *ndev, u32 obj_id)
> -{
> -	u32 buffer_status = 0;
> -	struct pch_can_priv *priv = netdev_priv(ndev);
> -
> -	/* Getting the message object status. */
> -	buffer_status = (u32) pch_can_get_buffer_status(priv);
> -
> -	return buffer_status & obj_id;
> -}
> -
> -
>  static netdev_tx_t pch_xmit(struct sk_buff *skb, struct net_device *ndev)
>  {
>  	int i, j;
> @@ -1031,17 +1025,16 @@ static netdev_tx_t pch_xmit(struct sk_buff *skb, struct net_device *ndev)
>  	if (can_dropped_invalid_skb(ndev, skb))
>  		return NETDEV_TX_OK;
>  
> -	if (priv->tx_obj == PCH_TX_OBJ_END) { /* Point tail Obj */
> -		while (pch_get_msg_obj_sts(ndev, (((1 << PCH_TX_OBJ_NUM)-1) <<
> -					   PCH_RX_OBJ_NUM)))
> -			udelay(500);
> +	if (priv->tx_obj == PCH_TX_OBJ_END) {
> +		if (ioread32(&priv->regs->treq2) & PCH_TREQ2_TX_MASK)
> +			netif_stop_queue(ndev);

David asked you in his previous review to implement a pure software
solution without relying on the hardware because it tends to be racy.

>  
> -		priv->tx_obj = PCH_TX_OBJ_START; /* Point head of Tx Obj ID */
> -		tx_buffer_avail = priv->tx_obj; /* Point Tail of Tx Obj */
> +		tx_buffer_avail = priv->tx_obj;
> +		priv->tx_obj = PCH_TX_OBJ_START;
>  	} else {
>  		tx_buffer_avail = priv->tx_obj;
> +		priv->tx_obj++;
>  	}
> -	priv->tx_obj++;
>  
>  	/* Reading the Msg Obj from the Msg RAM to the Interface register. */
>  	iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[1].cmask);

cheers, Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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