From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: [patch V2 21/21] can: c_can: Speed up tx buffer invalidation Date: Fri, 11 Apr 2014 08:13:22 -0000 Message-ID: <20140411080654.280509182@linutronix.de> References: <20140411080547.845836199@linutronix.de> Return-path: Received: from www.linutronix.de ([62.245.132.108]:52488 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755580AbaDKINK (ORCPT ); Fri, 11 Apr 2014 04:13:10 -0400 Content-Disposition: inline; filename=can-c_can-speed-up-tx-inval.patch Sender: linux-can-owner@vger.kernel.org List-ID: To: linux-can Cc: Alexander Stein , Oliver Hartkopp , Marc Kleine-Budde , Wolfgang Grandegger , Mark 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: Thomas Gleixner --- drivers/net/can/c_can/c_can.c | 54 ++++++++++++++++++++++++++++++------------ drivers/net/can/c_can/c_can.h | 1 2 files changed, 40 insertions(+), 15 deletions(-) Index: linux-2.6/drivers/net/can/c_can/c_can.c =================================================================== --- linux-2.6.orig/drivers/net/can/c_can/c_can.c +++ linux-2.6/drivers/net/can/c_can/c_can.c @@ -276,11 +276,34 @@ static inline void c_can_object_put(stru 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 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(s 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(stru * 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_ /* 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_devic 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++; Index: linux-2.6/drivers/net/can/c_can/c_can.h =================================================================== --- linux-2.6.orig/drivers/net/can/c_can/c_can.h +++ linux-2.6/drivers/net/can/c_can/c_can.h @@ -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);