Subject: Re: [PATCH] dm9000: add checksum offload support

From: Ben Dooks <[email-masked]>
Date: Wed, 01 Jul 2009 16:12:26 +0100

Mike Rapoport wrote:
> From: Yeasah Pell <[email-masked]>

Not a very informative message here. At least add a copy
of the subject, better to elaborate on the patch contents
here, such as the versions of the DM9000 that this will
work on.

> Signed-off-by: Yeasah Pell <[email-masked]>
> Signed-off-by: Mike Rapoport <[email-masked]>
> ---
>  drivers/net/dm9000.c |  105 +++++++++++++++++++++++++++++++++++++++++--------
>  drivers/net/dm9000.h |   18 +++++++++
>  2 files changed, 106 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/dm9000.c b/drivers/net/dm9000.c
> index dd771de..52b02d6 100644
> --- a/drivers/net/dm9000.c
> +++ b/drivers/net/dm9000.c
> @@ -92,6 +92,7 @@ typedef struct board_info {
>  	u16		tx_pkt_cnt;
>  	u16		queue_pkt_len;
>  	u16		queue_start_addr;
> +	u16		queue_ip_summed;
>  	u16		dbug_cnt;
>  	u8		io_mode;		/* 0:word, 2:byte */
>  	u8		phy_addr;
> @@ -124,6 +125,9 @@ typedef struct board_info {
>  
>  	struct mii_if_info mii;
>  	u32		msg_enable;
> +
> +	int		rx_csum;
> +	int		can_csum;
>  } board_info_t;
>  
>  /* debug code */
> @@ -460,6 +464,40 @@ static int dm9000_nway_reset(struct net_device *dev)
>  	return mii_nway_restart(&dm->mii);
>  }
>  
> +static uint32_t dm9000_get_rx_csum(struct net_device *dev)
> +{
> +	board_info_t *dm = to_dm9000_board(dev);
> +	return dm->rx_csum;
> +}
> +
> +static int dm9000_set_rx_csum(struct net_device *dev, uint32_t data)
> +{
> +	board_info_t *dm = to_dm9000_board(dev);
> +	unsigned long flags;
> +
> +	if (dm->can_csum) {
> +		dm->rx_csum = data;
> +
> +		spin_lock_irqsave(&dm->lock, flags);
> +		iow(dm, DM9000_RCSR, dm->rx_csum ? RCSR_CSUM : 0);
> +		spin_unlock_irqrestore(&dm->lock, flags);
> +
> +		return 0;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int dm9000_set_tx_csum(struct net_device *dev, uint32_t data)
> +{
> +	board_info_t *dm = to_dm9000_board(dev);
> +	int ret = -EOPNOTSUPP;
> +
> +	if (dm->can_csum)
> +		ret = ethtool_op_set_tx_csum(dev, data);
> +	return ret;
> +}
> +
>  static u32 dm9000_get_link(struct net_device *dev)
>  {
>  	board_info_t *dm = to_dm9000_board(dev);
> @@ -540,6 +578,10 @@ static const struct ethtool_ops dm9000_ethtool_ops = {
>   	.get_eeprom_len		= dm9000_get_eeprom_len,
>   	.get_eeprom		= dm9000_get_eeprom,
>   	.set_eeprom		= dm9000_set_eeprom,
> +	.get_rx_csum		= dm9000_get_rx_csum,
> +	.set_rx_csum		= dm9000_set_rx_csum,
> +	.get_tx_csum		= ethtool_op_get_tx_csum,
> +	.set_tx_csum		= dm9000_set_tx_csum,
>  };
>  
>  static void dm9000_show_carrier(board_info_t *db,
> @@ -685,6 +727,9 @@ dm9000_init_dm9000(struct net_device *dev)
>  	/* I/O mode */
>  	db->io_mode = ior(db, DM9000_ISR) >> 6;	/* ISR bit7:6 keeps I/O mode */
>  
> +	/* Checksum mode */
> +	dm9000_set_rx_csum(dev, db->rx_csum);
> +
>  	/* GPIO0 on pre-activate PHY */
>  	iow(db, DM9000_GPR, 0);	/* REG_1F bit0 activate phyxcer */
>  	iow(db, DM9000_GPCR, GPCR_GEP_CNTL);	/* Let GPIO0 output */
> @@ -743,6 +788,28 @@ static void dm9000_timeout(struct net_device *dev)
>  	spin_unlock_irqrestore(&db->lock, flags);
>  }
>  
> +static void dm9000_send_packet(struct net_device *dev,
> +			       int ip_summed,
> +			       u16 pkt_len)
> +{
> +	board_info_t *dm = to_dm9000_board(dev);
> +
> +	/* The DM9000 is not smart enough to leave fragmented packets alone. */
> +	if (ip_summed == CHECKSUM_NONE)
> +		iow(dm, DM9000_TCCR, 0);
> +	else
> +		iow(dm, DM9000_TCCR, TCCR_IP | TCCR_UDP | TCCR_TCP);

Is it worth keeping a local copy of this and
only writing on change, since a write to the device is
at-least two IO cycles?

> +	/* Set TX length to DM9000 */
> +	iow(dm, DM9000_TXPLL, pkt_len);
> +	iow(dm, DM9000_TXPLH, pkt_len >> 8);
> +
> +	/* Issue TX polling command */
> +	iow(dm, DM9000_TCR, TCR_TXREQ);	/* Cleared after TX complete */
> +
> +	dev->trans_start = jiffies;	/* save the time stamp */
> +}
> +
>  /*
>   *  Hardware start transmission.
>   *  Send a packet to media from the upper layer.
> @@ -769,17 +836,11 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	db->tx_pkt_cnt++;
>  	/* TX control: First packet immediately send, second packet queue */
>  	if (db->tx_pkt_cnt == 1) {
> -		/* Set TX length to DM9000 */
> -		iow(db, DM9000_TXPLL, skb->len);
> -		iow(db, DM9000_TXPLH, skb->len >> 8);
> -
> -		/* Issue TX polling command */
> -		iow(db, DM9000_TCR, TCR_TXREQ);	/* Cleared after TX complete */
> -
> -		dev->trans_start = jiffies;	/* save the time stamp */
> +		dm9000_send_packet(dev, skb->ip_summed, skb->len);
>  	} else {
>  		/* Second packet */
>  		db->queue_pkt_len = skb->len;
> +		db->queue_ip_summed = skb->ip_summed;
>  		netif_stop_queue(dev);
>  	}
>  
> @@ -809,12 +870,9 @@ static void dm9000_tx_done(struct net_device *dev, board_info_t *db)
>  			dev_dbg(db->dev, "tx done, NSR %02x\n", tx_status);
>  
>  		/* Queue packet check & send */
> -		if (db->tx_pkt_cnt > 0) {
> -			iow(db, DM9000_TXPLL, db->queue_pkt_len);
> -			iow(db, DM9000_TXPLH, db->queue_pkt_len >> 8);
> -			iow(db, DM9000_TCR, TCR_TXREQ);
> -			dev->trans_start = jiffies;
> -		}
> +		if (db->tx_pkt_cnt > 0)
> +			dm9000_send_packet(dev, db->queue_ip_summed,
> +					   db->queue_pkt_len);
>  		netif_wake_queue(dev);
>  	}
>  }
> @@ -846,14 +904,14 @@ dm9000_rx(struct net_device *dev)
>  		rxbyte = readb(db->io_data);
>  
>  		/* Status check: this byte must be 0 or 1 */
> -		if (rxbyte > DM9000_PKT_RDY) {
> +		if (rxbyte & DM9000_PKT_ERR) {
>  			dev_warn(db->dev, "status check fail: %d\n", rxbyte);
>  			iow(db, DM9000_RCR, 0x00);	/* Stop Device */
>  			iow(db, DM9000_ISR, IMR_PAR);	/* Stop INT request */
>  			return;
>  		}
>  
> -		if (rxbyte != DM9000_PKT_RDY)
> +		if (!(rxbyte & DM9000_PKT_RDY))
>  			return;
>  
>  		/* A packet ready now  & Get status/length */
> @@ -914,6 +972,12 @@ dm9000_rx(struct net_device *dev)
>  
>  			/* Pass to upper layer */
>  			skb->protocol = eth_type_trans(skb, dev);
> +			if (db->rx_csum) {
> +				if ((((rxbyte & 0x1c) << 3) & rxbyte) == 0)
> +					skb->ip_summed = CHECKSUM_UNNECESSARY;
> +				else
> +					skb->ip_summed = CHECKSUM_NONE;
> +			}
>  			netif_rx(skb);
>  			dev->stats.rx_packets++;
>  
> @@ -922,7 +986,7 @@ dm9000_rx(struct net_device *dev)
>  
>  			(db->dumpblk)(db->io_data, RxLen);
>  		}
> -	} while (rxbyte == DM9000_PKT_RDY);
> +	} while (rxbyte & DM9000_PKT_RDY);
>  }
>  
>  static irqreturn_t dm9000_interrupt(int irq, void *dev_id)
> @@ -1349,6 +1413,13 @@ dm9000_probe(struct platform_device *pdev)
>  		db->type = TYPE_DM9000E;
>  	}
>  
> +	/* dm9000a/b are capable of hardware checksum offload */
> +	if (db->type == TYPE_DM9000A || db->type == TYPE_DM9000B) {
> +		db->can_csum = 1;
> +		db->rx_csum = 1;
> +		ndev->features |= NETIF_F_IP_CSUM;

can ndev->features be checked and db->can_csum be removed?

> +	}
> +
>  	/* from this point we assume that we have found a DM9000 */
>  
>  	/* driver system function */
> diff --git a/drivers/net/dm9000.h b/drivers/net/dm9000.h
> index ba25cf5..80817c2 100644
> --- a/drivers/net/dm9000.h
> +++ b/drivers/net/dm9000.h
> @@ -45,6 +45,10 @@
>  #define DM9000_CHIPR           0x2C
>  #define DM9000_SMCR            0x2F
>  
> +#define DM9000_ETXCSR          0x30
> +#define DM9000_TCCR	       0x31
> +#define DM9000_RCSR	       0x32
> +
>  #define CHIPR_DM9000A	       0x19
>  #define CHIPR_DM9000B	       0x1B
>  
> @@ -131,7 +135,21 @@
>  
>  #define GPCR_GEP_CNTL       (1<<0)
>  
> +#define TCCR_IP		    (1<<0)
> +#define TCCR_TCP	    (1<<1)
> +#define TCCR_UDP	    (1<<2)
> +
> +#define RCSR_UDP_BAD	    (1<<7)
> +#define RCSR_TCP_BAD	    (1<<6)
> +#define RCSR_IP_BAD	    (1<<5)
> +#define RCSR_UDP	    (1<<4)
> +#define RCSR_TCP	    (1<<3)
> +#define RCSR_IP		    (1<<2)
> +#define RCSR_CSUM	    (1<<1)
> +#define RCSR_DISCARD	    (1<<0)
> +
>  #define DM9000_PKT_RDY		0x01	/* Packet ready to receive */
> +#define DM9000_PKT_ERR		0x02
>  #define DM9000_PKT_MAX		1536	/* Received packet max size */
>  
>  /* DM9000A / DM9000B definitions */