Commit 28e86e9a authored by Dario Binacchi's avatar Dario Binacchi Committed by Marc Kleine-Budde
Browse files

can: c_can: support tx ring algorithm 

The algorithm is already used successfully by other CAN drivers
(e.g. mcp251xfd). Its implementation was kindly suggested to me by
Marc Kleine-Budde following a patch I had previously submitted. You can
find every detail at https://lore.kernel.org/patchwork/patch/1422929/.

The idea is that after this patch, it will be easier to patch the driver
to use the message object memory as a true FIFO.

Link: https://lore.kernel.org/r/20210807130800.5246-4-dariobin@libero.it


Suggested-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: default avatarDario Binacchi <dariobin@libero.it>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent a54cdbba

drivers/net/can/c_can/c_can.h

+32 −1
Original line number Diff line number Diff line
@@ -176,6 +176,13 @@ struct c_can_raminit { 
	bool needs_pulse;

};



/* c_can tx ring structure */

struct c_can_tx_ring {

	unsigned int head;

	unsigned int tail;

	unsigned int obj_num;

};



/* c_can private data structure */

struct c_can_priv {

	struct can_priv can;	/* must be the first member */
@@ -190,10 +197,10 @@ struct c_can_priv { 
	unsigned int msg_obj_tx_first;

	unsigned int msg_obj_tx_last;

	u32 msg_obj_rx_mask;

	atomic_t tx_active;

	atomic_t sie_pending;

	unsigned long tx_dir;

	int last_status;

	struct c_can_tx_ring tx;

	u16 (*read_reg)(const struct c_can_priv *priv, enum reg index);

	void (*write_reg)(const struct c_can_priv *priv, enum reg index, u16 val);

	u32 (*read_reg32)(const struct c_can_priv *priv, enum reg index);
@@ -219,4 +226,28 @@ int c_can_power_down(struct net_device *dev); 


void c_can_set_ethtool_ops(struct net_device *dev);



static inline u8 c_can_get_tx_head(const struct c_can_tx_ring *ring)

{

	return ring->head & (ring->obj_num - 1);

}



static inline u8 c_can_get_tx_tail(const struct c_can_tx_ring *ring)

{

	return ring->tail & (ring->obj_num - 1);

}



static inline u8 c_can_get_tx_free(const struct c_can_tx_ring *ring)

{

	u8 head = c_can_get_tx_head(ring);

	u8 tail = c_can_get_tx_tail(ring);



	/* This is not a FIFO. C/D_CAN sends out the buffers

	 * prioritized. The lowest buffer number wins.

	 */

	if (head < tail)

		return 0;



	return ring->obj_num - head;

}



#endif /* C_CAN_H */

drivers/net/can/c_can/c_can_main.c

+50 −17
Original line number Diff line number Diff line
@@ -427,24 +427,50 @@ static void c_can_setup_receive_object(struct net_device *dev, int iface, 
	c_can_object_put(dev, iface, obj, IF_COMM_RCV_SETUP);

}



static bool c_can_tx_busy(const struct c_can_priv *priv,

			  const struct c_can_tx_ring *tx_ring)

{

	if (c_can_get_tx_free(tx_ring) > 0)

		return false;



	netif_stop_queue(priv->dev);



	/* Memory barrier before checking tx_free (head and tail) */

	smp_mb();



	if (c_can_get_tx_free(tx_ring) == 0) {

		netdev_dbg(priv->dev,

			   "Stopping tx-queue (tx_head=0x%08x, tx_tail=0x%08x, len=%d).\n",

			   tx_ring->head, tx_ring->tail,

			   tx_ring->head - tx_ring->tail);

		return true;

	}



	netif_start_queue(priv->dev);

	return false;

}



static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,

				    struct net_device *dev)

{

	struct can_frame *frame = (struct can_frame *)skb->data;

	struct c_can_priv *priv = netdev_priv(dev);

	struct c_can_tx_ring *tx_ring = &priv->tx;

	u32 idx, obj;



	if (can_dropped_invalid_skb(dev, skb))

		return NETDEV_TX_OK;

	/* This is not a FIFO. C/D_CAN sends out the buffers

	 * prioritized. The lowest buffer number wins.

	 */

	idx = fls(atomic_read(&priv->tx_active));

	obj = idx + priv->msg_obj_tx_first;



	/* If this is the last buffer, stop the xmit queue */

	if (idx == priv->msg_obj_tx_num - 1)

	if (c_can_tx_busy(priv, tx_ring))

		return NETDEV_TX_BUSY;



	idx = c_can_get_tx_head(tx_ring);

	tx_ring->head++;

	if (c_can_get_tx_free(tx_ring) == 0)

		netif_stop_queue(dev);



	obj = idx + priv->msg_obj_tx_first;



	/* Store the message in the interface so we can call

	 * can_put_echo_skb(). We must do this before we enable

	 * transmit as we might race against do_tx().
@@ -453,8 +479,6 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb, 
	priv->dlc[idx] = frame->len;

	can_put_echo_skb(skb, dev, idx, 0);



	/* Update the active bits */

	atomic_add(BIT(idx), &priv->tx_active);

	/* Start transmission */

	c_can_object_put(dev, IF_TX, obj, IF_COMM_TX);
@@ -567,6 +591,7 @@ static int c_can_software_reset(struct net_device *dev) 
static int c_can_chip_config(struct net_device *dev)

{

	struct c_can_priv *priv = netdev_priv(dev);

	struct c_can_tx_ring *tx_ring = &priv->tx;

	int err;



	err = c_can_software_reset(dev);
@@ -598,7 +623,8 @@ static int c_can_chip_config(struct net_device *dev) 
	priv->write_reg(priv, C_CAN_STS_REG, LEC_UNUSED);



	/* Clear all internal status */

	atomic_set(&priv->tx_active, 0);

	tx_ring->head = 0;

	tx_ring->tail = 0;

	priv->tx_dir = 0;



	/* set bittiming params */
@@ -696,14 +722,14 @@ static int c_can_get_berr_counter(const struct net_device *dev, 
static void c_can_do_tx(struct net_device *dev)

{

	struct c_can_priv *priv = netdev_priv(dev);

	struct c_can_tx_ring *tx_ring = &priv->tx;

	struct net_device_stats *stats = &dev->stats;

	u32 idx, obj, pkts = 0, bytes = 0, pend, clr;

	u32 idx, obj, pkts = 0, bytes = 0, pend;



	if (priv->msg_obj_tx_last > 32)

		pend = priv->read_reg32(priv, C_CAN_INTPND3_REG);

	else

		pend = priv->read_reg(priv, C_CAN_INTPND2_REG);

	clr = pend;



	while ((idx = ffs(pend))) {

		idx--;
@@ -723,11 +749,14 @@ static void c_can_do_tx(struct net_device *dev) 
	if (!pkts)

		return;



	/* Clear the bits in the tx_active mask */

	atomic_sub(clr, &priv->tx_active);



	if (clr & BIT(priv->msg_obj_tx_num - 1))

		netif_wake_queue(dev);

	tx_ring->tail += pkts;

	if (c_can_get_tx_free(tx_ring)) {

		/* Make sure that anybody stopping the queue after

		 * this sees the new tx_ring->tail.

		 */

		smp_mb();

		netif_wake_queue(priv->dev);

	}



	stats->tx_bytes += bytes;

	stats->tx_packets += pkts;
@@ -1208,6 +1237,10 @@ struct net_device *alloc_c_can_dev(int msg_obj_num) 
	priv->msg_obj_tx_last =

		priv->msg_obj_tx_first + priv->msg_obj_tx_num - 1;



	priv->tx.head = 0;

	priv->tx.tail = 0;

	priv->tx.obj_num = msg_obj_tx_num;



	netif_napi_add(dev, &priv->napi, c_can_poll, priv->msg_obj_rx_num);



	priv->dev = dev;