Commit 93941597 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Marc Kleine-Budde
Browse files

can: c_can: Speed up tx buffer invalidation 



It's suffcient to kill the TXIE bit in the message control register
even if the documentation of C and D CAN says that it's not allowed to
do that while MSGVAL is set. Reality tells a different story and this
change gives us another 2% of CPU back for not waiting on I/O.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarAlexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 35bdafb5

drivers/net/can/c_can/c_can.c

+39 −15
Original line number Diff line number Diff line
@@ -276,11 +276,34 @@ static inline void c_can_object_put(struct net_device *dev, int iface, 
	c_can_obj_update(dev, iface, cmd | IF_COMM_WR, obj);

}



/*

 * Note: According to documentation clearing TXIE while MSGVAL is set

 * is not allowed, but works nicely on C/DCAN. And that lowers the I/O

 * load significantly.

 */

static void c_can_inval_tx_object(struct net_device *dev, int iface, int obj)

{

	struct c_can_priv *priv = netdev_priv(dev);



	priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), 0);

	c_can_object_put(dev, iface, obj, IF_COMM_INVAL);

}



static void c_can_inval_msg_object(struct net_device *dev, int iface, int obj)

{

	struct c_can_priv *priv = netdev_priv(dev);



	priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), 0);

	priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), 0);

	c_can_inval_tx_object(dev, iface, obj);

}



static void c_can_setup_tx_object(struct net_device *dev, int iface,

				  struct can_frame *frame, int obj)

				  struct can_frame *frame, int idx)

{

	struct c_can_priv *priv = netdev_priv(dev);

	u16 ctrl = IF_MCONT_TX | frame->can_dlc;

	bool rtr = frame->can_id & CAN_RTR_FLAG;

	u32 arb = IF_ARB_MSGVAL;

	int i;
@@ -291,9 +314,20 @@ static void c_can_setup_tx_object(struct net_device *dev, int iface, 
		arb |= (frame->can_id & CAN_SFF_MASK) << 18;

	}



	if (!(frame->can_id & CAN_RTR_FLAG))

	if (!rtr)

		arb |= IF_ARB_TRANSMIT;



	/*

	 * If we change the DIR bit, we need to invalidate the buffer

	 * first, i.e. clear the MSGVAL flag in the arbiter.

	 */

	if (rtr != (bool)test_bit(idx, &priv->tx_dir)) {

		u32 obj = idx + C_CAN_MSG_OBJ_TX_FIRST;



		c_can_inval_msg_object(dev, iface, obj);

		change_bit(idx, &priv->tx_dir);

	}



	priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), arb);

	priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), arb >> 16);
@@ -401,17 +435,6 @@ 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 void c_can_inval_msg_object(struct net_device *dev, int iface, int obj)

{

	struct c_can_priv *priv = netdev_priv(dev);



	priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), 0);

	priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), 0);

	priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), 0);



	c_can_object_put(dev, iface, obj, IF_COMM_INVAL);

}



static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,

				    struct net_device *dev)

{
@@ -436,7 +459,7 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb, 
	 * can_put_echo_skb(). We must do this before we enable

	 * transmit as we might race against do_tx().

	 */

	c_can_setup_tx_object(dev, IF_TX, frame, obj);

	c_can_setup_tx_object(dev, IF_TX, frame, idx);

	priv->dlc[idx] = frame->can_dlc;

	can_put_echo_skb(skb, dev, idx);
@@ -563,6 +586,7 @@ static int c_can_chip_config(struct net_device *dev) 
	/* Clear all internal status */

	atomic_set(&priv->tx_active, 0);

	priv->rxmasked = 0;

	priv->tx_dir = 0;



	/* set bittiming params */

	return c_can_set_bittiming(dev);
@@ -654,7 +678,7 @@ static void c_can_do_tx(struct net_device *dev) 
		idx--;

		pend &= ~(1 << idx);

		obj = idx + C_CAN_MSG_OBJ_TX_FIRST;

		c_can_inval_msg_object(dev, IF_RX, obj);

		c_can_inval_tx_object(dev, IF_RX, obj);

		can_get_echo_skb(dev, idx);

		bytes += priv->dlc[idx];

		pkts++;

drivers/net/can/c_can/c_can.h

+1 −0
Original line number Diff line number Diff line
@@ -174,6 +174,7 @@ struct c_can_priv { 
	struct net_device *dev;

	struct device *device;

	atomic_t tx_active;

	unsigned long tx_dir;

	int last_status;

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

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

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