It was <2021-01-15 pią 17:27>, when Jakub Kicinski wrote:
> On Wed, 13 Jan 2021 19:40:28 +0100 Łukasz Stelmach wrote:
>> ASIX AX88796[1] is a versatile ethernet adapter chip, that can be
>> connected to a CPU with a 8/16-bit bus or with an SPI. This driver
>> supports SPI connection.
>> 
>> The driver has been ported from the vendor kernel for ARTIK5[2]
>> boards. Several changes were made to adapt it to the current kernel
>> which include:
>> 
>> + updated DT configuration,
>> + clock configuration moved to DT,
>> + new timer, ethtool and gpio APIs,
>> + dev_* instead of pr_* and custom printk() wrappers,
>> + removed awkward vendor power managemtn.
>> + introduced ethtool tunable to control SPI compression
>> 

[...]

>> 
>> The other ax88796 driver is for NE2000 compatible AX88796L chip. These
>> chips are not compatible. Hence, two separate drivers are required.
>> 
>> Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>
>> +static u32 ax88796c_get_priv_flags(struct net_device *ndev)
>> +{
>> +	struct ax88796c_device *ax_local = to_ax88796c_device(ndev);
>> +
>> +        return ax_local->priv_flags;
>
> stray indent
>
>> +}

Done.

>> +#define MAX(x,y) ((x) > (y) ? (x) : (y))
>
> Please use the standard linux max / max_t macros.

Done.

>> +static struct sk_buff *
>> +ax88796c_tx_fixup(struct net_device *ndev, struct sk_buff_head *q)
>> +{
>> +	struct ax88796c_device *ax_local = to_ax88796c_device(ndev);
>> +	u8 spi_len = ax_local->ax_spi.comp ? 1 : 4;
>> +	struct sk_buff *skb;
>> +	struct tx_pkt_info *info;
>> +	struct skb_data *entry;
>> +	u16 pkt_len;
>> +	u8 padlen, seq_num;
>> +	u8 need_pages;
>> +	int headroom;
>> +	int tailroom;
>> +
>> +	if (skb_queue_empty(q))
>> +		return NULL;
>> +
>> +	skb = skb_peek(q);
>> +	pkt_len = skb->len;
>> +	need_pages = (pkt_len + TX_OVERHEAD + 127) >> 7;
>> +	if (ax88796c_check_free_pages(ax_local, need_pages) != 0)
>> +		return NULL;
>> +
>> +	headroom = skb_headroom(skb);
>> +	tailroom = skb_tailroom(skb);
>> +	padlen = round_up(pkt_len, 4) - pkt_len;
>> +	seq_num = ++ax_local->seq_num & 0x1F;
>> +
>> +	info = (struct tx_pkt_info *)skb->cb;
>> +	info->pkt_len = pkt_len;
>> +
>> +	if (skb_cloned(skb) ||
>> +	    (headroom < (TX_OVERHEAD + spi_len)) ||
>> +	    (tailroom < (padlen + TX_EOP_SIZE))) {
>> +		size_t h = MAX((TX_OVERHEAD + spi_len) - headroom,0);
>> +		size_t t = MAX((padlen + TX_EOP_SIZE) - tailroom,0);
>> +
>> +		if (pskb_expand_head(skb, h, t, GFP_KERNEL))
>> +			return NULL;
>> +	}
>> +
>> +	info->seq_num = seq_num;
>> +	ax88796c_proc_tx_hdr(info, skb->ip_summed);
>> +
>> +	/* SOP and SEG header */
>> +	memcpy(skb_push(skb, TX_OVERHEAD), &info->sop, TX_OVERHEAD);
>
> why use skb->cb to store info? why not declare it on the stack?
>

Done.

>> +	/* Write SPI TXQ header */
>> +	memcpy(skb_push(skb, spi_len), ax88796c_tx_cmd_buf, spi_len);
>> +
>> +	/* Make 32-bit alignment */
>> +	skb_put(skb, padlen);
>> +
>> +	/* EOP header */
>> +	memcpy(skb_put(skb, TX_EOP_SIZE), &info->eop, TX_EOP_SIZE);
>> +
>> +	skb_unlink(skb, q);
>> +
>> +	entry = (struct skb_data *)skb->cb;
>> +	memset(entry, 0, sizeof(*entry));
>> +	entry->len = pkt_len;
>> +
>> +	if (netif_msg_pktdata(ax_local)) {
>> +		char pfx[IFNAMSIZ + 7];
>> +
>> +		snprintf(pfx, sizeof(pfx), "%s:     ", ndev->name);
>> +
>> +		netdev_info(ndev, "TX packet len %d, total len %d, seq %d\n",
>> +			    pkt_len, skb->len, seq_num);
>> +
>> +		netdev_info(ndev, "  SPI Header:\n");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       skb->data, 4, 0);
>> +
>> +		netdev_info(ndev, "  TX SOP:\n");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       skb->data + 4, TX_OVERHEAD, 0);
>> +
>> +		netdev_info(ndev, "  TX packet:\n");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       skb->data + 4 + TX_OVERHEAD,
>> +			       skb->len - TX_EOP_SIZE - 4 - TX_OVERHEAD, 0);
>> +
>> +		netdev_info(ndev, "  TX EOP:\n");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       skb->data + skb->len - 4, 4, 0);
>> +	}
>> +
>> +	return skb;
>> +}
>> +
>> +static int ax88796c_hard_xmit(struct ax88796c_device *ax_local)
>> +{
>> +	struct sk_buff *tx_skb;
>> +	struct skb_data *entry;
>> +
>> +	WARN_ON(!mutex_is_locked(&ax_local->spi_lock));
>> +
>> +	tx_skb = ax88796c_tx_fixup(ax_local->ndev, &ax_local->tx_wait_q);
>> +
>> +	if (!tx_skb)
>> +		return 0;
>
> tx_dropped++ ?
>

Done.

>> +	entry = (struct skb_data *)tx_skb->cb;
>> +
>> +	AX_WRITE(&ax_local->ax_spi,
>> +		 (TSNR_TXB_START | TSNR_PKT_CNT(1)), P0_TSNR);
>> +
>> +	axspi_write_txq(&ax_local->ax_spi, tx_skb->data, tx_skb->len);
>> +
>> +	if (((AX_READ(&ax_local->ax_spi, P0_TSNR) & TXNR_TXB_IDLE) == 0) ||
>> +	    ((ISR_TXERR & AX_READ(&ax_local->ax_spi, P0_ISR)) != 0)) {
>> +		/* Ack tx error int */
>> +		AX_WRITE(&ax_local->ax_spi, ISR_TXERR, P0_ISR);
>> +
>> +		ax_local->stats.tx_dropped++;
>> +
>> +		netif_err(ax_local, tx_err, ax_local->ndev,
>> +			  "TX FIFO error, re-initialize the TX bridge\n");
>
> rate limit
>

Done.

>> +		/* Reinitial tx bridge */
>> +		AX_WRITE(&ax_local->ax_spi, TXNR_TXB_REINIT |
>> +			AX_READ(&ax_local->ax_spi, P0_TSNR), P0_TSNR);
>> +		ax_local->seq_num = 0;
>> +	} else {
>> +		ax_local->stats.tx_packets++;
>> +		ax_local->stats.tx_bytes += entry->len;
>> +	}
>> +
>> +	entry->state = tx_done;
>> +	dev_kfree_skb(tx_skb);
>
> dev_consume_skb() is better in cases the xmission was correct.
> kfree_skb() shows up in packet drop monitor.
>

This one is OK as it is because

1. dev_kfree_skb() is consume_skb()

    include/linux/skbuff.h:#define dev_kfree_skb(a) consume_skb(a)

2. dev_consume_skb() does not exist. There are dev_consume_skb_irq() and
dev_consume_skb_any(). The former can be used in IRQs, the latter
anywher and de facto calls the former if in IRQ. If not, it calls
dev_kfree_skb() (see above)

3. Last but not least. kfree_skb() and consume_skb() become the same
without CONFIG_TRACEPOINTS (commit be769db2f958).

>> +
>> +	return 1;
>> +}
>
>> +static void
>> +ax88796c_skb_return(struct ax88796c_device *ax_local, struct sk_buff *skb,
>> +		    struct rx_header *rxhdr)
>> +{
>> +	struct net_device *ndev = ax_local->ndev;
>> +	int status;
>> +
>> +	do {
>> +		if (!(ndev->features & NETIF_F_RXCSUM))
>> +			break;
>> +
>> +		/* checksum error bit is set */
>> +		if ((rxhdr->flags & RX_HDR3_L3_ERR) ||
>> +		    (rxhdr->flags & RX_HDR3_L4_ERR))
>> +			break;
>> +
>> +		/* Other types may be indicated by more than one bit. */
>> +		if ((rxhdr->flags & RX_HDR3_L4_TYPE_TCP) ||
>> +		    (rxhdr->flags & RX_HDR3_L4_TYPE_UDP))
>> +			skb->ip_summed = CHECKSUM_UNNECESSARY;
>> +	} while (0);
>> +
>> +	ax_local->stats.rx_packets++;
>> +	ax_local->stats.rx_bytes += skb->len;
>> +	skb->dev = ndev;
>> +
>> +	skb->protocol = eth_type_trans(skb, ax_local->ndev);
>> +
>> +	netif_info(ax_local, rx_status, ndev, "< rx, len %zu, type 0x%x\n",
>> +		   skb->len + sizeof(struct ethhdr), skb->protocol);
>> +
>> +	status = netif_rx_ni(skb);
>> +	if (status != NET_RX_SUCCESS)
>> +		netif_info(ax_local, rx_err, ndev,
>> +			   "netif_rx status %d\n", status);
>
> rate limit
>

Done.

>> +}
>> +
>> +static void
>> +ax88796c_rx_fixup(struct ax88796c_device *ax_local, struct sk_buff *rx_skb)
>> +{
>> +	struct rx_header *rxhdr = (struct rx_header *)rx_skb->data;
>> +	struct net_device *ndev = ax_local->ndev;
>> +	u16 len;
>> +
>> +	be16_to_cpus(&rxhdr->flags_len);
>> +	be16_to_cpus(&rxhdr->seq_lenbar);
>> +	be16_to_cpus(&rxhdr->flags);
>> +
>> +	if (((rxhdr->flags_len) & RX_HDR1_PKT_LEN) !=
>> +			 (~(rxhdr->seq_lenbar) & 0x7FF)) {
>
> Lots of unnecessary parenthesis.
>

Done.

>> +		netif_err(ax_local, rx_err, ndev, "Header error\n");
>> +
>> +		ax_local->stats.rx_frame_errors++;
>> +		kfree_skb(rx_skb);
>> +		return;
>> +	}
>> +
>> +	if ((rxhdr->flags_len & RX_HDR1_MII_ERR) ||
>> +	    (rxhdr->flags_len & RX_HDR1_CRC_ERR)) {
>> +		netif_err(ax_local, rx_err, ndev, "CRC or MII error\n");
>> +
>> +		ax_local->stats.rx_crc_errors++;
>> +		kfree_skb(rx_skb);
>> +		return;
>> +	}
>> +
>> +	len = rxhdr->flags_len & RX_HDR1_PKT_LEN;
>> +	if (netif_msg_pktdata(ax_local)) {
>> +		char pfx[IFNAMSIZ + 7];
>> +
>> +		snprintf(pfx, sizeof(pfx), "%s:     ", ndev->name);
>> +		netdev_info(ndev, "RX data, total len %d, packet len %d\n",
>> +			    rx_skb->len, len);
>> +
>> +		netdev_info(ndev, "  Dump RX packet header:");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       rx_skb->data, sizeof(*rxhdr), 0);
>> +
>> +		netdev_info(ndev, "  Dump RX packet:");
>> +		print_hex_dump(KERN_INFO, pfx, DUMP_PREFIX_OFFSET, 16, 1,
>> +			       rx_skb->data + sizeof(*rxhdr), len, 0);
>> +	}
>> +
>> +	skb_pull(rx_skb, sizeof(*rxhdr));
>> +	pskb_trim(rx_skb, len);
>> +
>> +	ax88796c_skb_return(ax_local, rx_skb, rxhdr);
>> +}
>> +
>> +static int ax88796c_receive(struct net_device *ndev)
>> +{
>> +	struct ax88796c_device *ax_local = to_ax88796c_device(ndev);
>> +	struct skb_data *entry;
>> +	u16 w_count, pkt_len;
>> +	struct sk_buff *skb;
>> +	u8 pkt_cnt;
>> +
>> +	WARN_ON(!mutex_is_locked(&ax_local->spi_lock));
>> +
>> +	/* check rx packet and total word count */
>> +	AX_WRITE(&ax_local->ax_spi, AX_READ(&ax_local->ax_spi, P0_RTWCR)
>> +		  | RTWCR_RX_LATCH, P0_RTWCR);
>> +
>> +	pkt_cnt = AX_READ(&ax_local->ax_spi, P0_RXBCR2) & RXBCR2_PKT_MASK;
>> +	if (!pkt_cnt)
>> +		return 0;
>> +
>> +	pkt_len = AX_READ(&ax_local->ax_spi, P0_RCPHR) & 0x7FF;
>> +
>> +	w_count = ((pkt_len + 6 + 3) & 0xFFFC) >> 1;
>
> w_count = round_up(pkt_len + 6, 4) >> 1;
>

Done.

>> +	skb = netdev_alloc_skb(ndev, (w_count * 2));
>
> parenthesis unnecessary
>

Done.

>> +	if (!skb) {
>> +		AX_WRITE(&ax_local->ax_spi, RXBCR1_RXB_DISCARD, P0_RXBCR1);
>
> Increment rx_dropped counter here?
>

Done.

>> +		return 0;
>> +	}
>> +	entry = (struct skb_data *)skb->cb;
>> +
>> +	AX_WRITE(&ax_local->ax_spi, RXBCR1_RXB_START | w_count, P0_RXBCR1);
>> +
>> +	axspi_read_rxq(&ax_local->ax_spi,
>> +		       skb_put(skb, w_count * 2), skb->len);
>> +
>> +	/* Check if rx bridge is idle */
>> +	if ((AX_READ(&ax_local->ax_spi, P0_RXBCR2) & RXBCR2_RXB_IDLE) == 0) {
>> +		netif_err(ax_local, rx_err, ndev,
>> +			  "Rx Bridge is not idle\n");
>
> rate limit?
>

Ok.

>> +		AX_WRITE(&ax_local->ax_spi, RXBCR2_RXB_REINIT, P0_RXBCR2);
>> +
>> +		entry->state = rx_err;
>> +	} else {
>> +		entry->state = rx_done;
>> +	}
>> +
>> +	AX_WRITE(&ax_local->ax_spi, ISR_RXPKT, P0_ISR);
>> +
>> +	ax88796c_rx_fixup(ax_local, skb);
>> +
>> +	return 1;
>> +}
>> +
>> +static int ax88796c_process_isr(struct ax88796c_device *ax_local)
>> +{
>> +	struct net_device *ndev = ax_local->ndev;
>> +	u8 done = 0;
>
> The logic associated with this variable is "is there more to do" rather
> than "done", no?
>

ax88796c_receive() returns 1, if there may be something more to do. So
yes, let's rename it to todo.

>> +	u16 isr;
>> +
>> +	WARN_ON(!mutex_is_locked(&ax_local->spi_lock));
>> +
>> +	isr = AX_READ(&ax_local->ax_spi, P0_ISR);
>> +	AX_WRITE(&ax_local->ax_spi, isr, P0_ISR);
>> +
>> +	netif_dbg(ax_local, intr, ndev, "  ISR 0x%04x\n", isr);
>> +
>> +	if (isr & ISR_TXERR) {
>> +		netif_dbg(ax_local, intr, ndev, "  TXERR interrupt\n");
>> +		AX_WRITE(&ax_local->ax_spi, TXNR_TXB_REINIT, P0_TSNR);
>> +		ax_local->seq_num = 0x1f;
>> +	}
>> +
>> +	if (isr & ISR_TXPAGES) {
>> +		netif_dbg(ax_local, intr, ndev, "  TXPAGES interrupt\n");
>> +		set_bit(EVENT_TX, &ax_local->flags);
>> +	}
>> +
>> +	if (isr & ISR_LINK) {
>> +		netif_dbg(ax_local, intr, ndev, "  Link change interrupt\n");
>> +		phy_mac_interrupt(ax_local->ndev->phydev);
>> +	}
>> +
>> +	if (isr & ISR_RXPKT) {
>> +		netif_dbg(ax_local, intr, ndev, "  RX interrupt\n");
>> +		done = ax88796c_receive(ax_local->ndev);
>> +	}
>> +
>> +	return done;
>> +}
>
>> +static void ax88796c_work(struct work_struct *work)
>> +{
>> +	struct ax88796c_device *ax_local =
>> +			container_of(work, struct ax88796c_device, ax_work);
>> +
>> +	mutex_lock(&ax_local->spi_lock);
>> +
>> +	if (test_bit(EVENT_SET_MULTI, &ax_local->flags)) {
>> +		ax88796c_set_hw_multicast(ax_local->ndev);
>> +		clear_bit(EVENT_SET_MULTI, &ax_local->flags);
>> +	}
>> +
>> +	if (test_bit(EVENT_INTR, &ax_local->flags)) {
>> +		AX_WRITE(&ax_local->ax_spi, IMR_MASKALL, P0_IMR);
>> +
>> +		while (1) {
>> +			if (!ax88796c_process_isr(ax_local))
>> +				break;
>
> while (ax88796c_process_isr(ax_local))
> 	/* nothing */;
> ?
>

Ok.

>> +		}
>> +
>> +		clear_bit(EVENT_INTR, &ax_local->flags);
>> +
>> +		AX_WRITE(&ax_local->ax_spi, IMR_DEFAULT, P0_IMR);
>> +
>> +		enable_irq(ax_local->ndev->irq);
>> +	}
>> +
>> +	if (test_bit(EVENT_TX, &ax_local->flags)) {
>> +		while (skb_queue_len(&ax_local->tx_wait_q)) {
>> +			if (!ax88796c_hard_xmit(ax_local))
>> +				break;
>> +		}
>> +
>> +		clear_bit(EVENT_TX, &ax_local->flags);
>> +
>> +		if (netif_queue_stopped(ax_local->ndev) &&
>> +		    (skb_queue_len(&ax_local->tx_wait_q) < TX_QUEUE_LOW_WATER))
>> +			netif_wake_queue(ax_local->ndev);
>> +	}
>> +
>> +	mutex_unlock(&ax_local->spi_lock);
>> +}
>
>> +static void ax88796c_set_csums(struct ax88796c_device *ax_local)
>> +{
>> +	struct net_device *ndev = ax_local->ndev;
>> +
>> +	WARN_ON(!mutex_is_locked(&ax_local->spi_lock));
>
> lockdep_assert_held() in all those cases
>

Done.

>> +static void ax88796c_free_skb_queue(struct sk_buff_head *q)
>> +{
>> +	struct sk_buff *skb;
>> +
>> +	while (q->qlen) {
>> +		skb = skb_dequeue(q);
>> +		kfree_skb(skb);
>> +	}
>
> __skb_queue_purge()
>

Done.

>> +}
>> +
>> +static int
>> +ax88796c_close(struct net_device *ndev)
>> +{
>> +	struct ax88796c_device *ax_local = to_ax88796c_device(ndev);
>> +
>> +	netif_stop_queue(ndev);
>> +	phy_stop(ndev->phydev);
>> +
>> +	mutex_lock(&ax_local->spi_lock);
>> +
>> +	/* Disable MAC interrupts */
>> +	AX_WRITE(&ax_local->ax_spi, IMR_MASKALL, P0_IMR);
>> +	ax88796c_free_skb_queue(&ax_local->tx_wait_q);
>> +	ax88796c_soft_reset(ax_local);
>> +
>> +	mutex_unlock(&ax_local->spi_lock);
>> +
>> +	free_irq(ndev->irq, ndev);
>> +
>> +	return 0;
>> +}
>
>> +struct ax88796c_device {
>> +	struct spi_device	*spi;
>> +	struct net_device	*ndev;
>> +	struct net_device_stats	stats;
>
> You need to use 64 bit stats, like struct rtnl_link_stats64.
> On a 32bit system at 100Mbps ulong can wrap in minutes.
>

Let me see. At first glance

git grep -l ndo_get_stats\\\> drivers/net/ethernet/  | xargs grep -li SPEED_100\\\>

quite a number of Fast Ethernet drivers use net_device_stats. Let me
calculate.

- bytes
  100Mbps is ~10MiB/s
  sending 4GiB at 10MiB/s takes 27 minutes

- packets
  minimum frame size is 84 bytes (840 bits on the wire) on 100Mbps means
  119048 pps at this speed it takse 10 hours to transmit 2^32 packets

Anyway, I switched to rtnl_link_stats64. Tell me, is it OK to just
memcpy() in .ndo_get_stats64?

>> +	struct work_struct	ax_work;
>
> I don't see you ever canceling / flushing this work.
> You should do that at least on driver remove if not close.

Done.

Does it mean most drivers do it wrong?

    git grep INIT_WORK drivers/net/ethernet/ | \
    sed -e 's/\(^[^:]*\):[^>]*->\([^,]*\),.*/\1        \2/' | \
    while read file var; do \
        grep -H $var $file;
    done | grep INIT_WORK\\\|cancel_work


>> +	struct mutex		spi_lock; /* device access */
>> +
>> +	struct sk_buff_head	tx_wait_q;
>> +
>> +	struct axspi_data	ax_spi;
>> +
>> +	struct mii_bus		*mdiobus;
>> +	struct phy_device	*phydev;
>> +
>> +	int			msg_enable;
>> +
>> +	u16			seq_num;
>> +
>> +	u8			multi_filter[AX_MCAST_FILTER_SIZE];
>> +
>> +	int			link;
>> +	int			speed;
>> +	int			duplex;
>> +	int			pause;
>> +	int			asym_pause;
>> +	int			flowctrl;
>> +		#define AX_FC_NONE		0
>> +		#define AX_FC_RX		BIT(0)
>> +		#define AX_FC_TX		BIT(1)
>> +		#define AX_FC_ANEG		BIT(2)
>> +
>> +	u32			priv_flags;
>> +		#define AX_CAP_COMP		BIT(0)
>> +		#define AX_PRIV_FLAGS_MASK	(AX_CAP_COMP)
>> +
>> +	unsigned long		flags;
>> +		#define EVENT_INTR		BIT(0)
>> +		#define EVENT_TX		BIT(1)
>> +		#define EVENT_SET_MULTI		BIT(2)
>> +
>> +};
>
>> +struct skb_data {
>> +	enum skb_state state;
>> +	struct net_device *ndev;
>> +	struct sk_buff *skb;
>
> Don't think you ever use the skb or ndev from this structure.
>

Done.

>> +	size_t len;
>> +};
>
>

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics