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Message-Id: <1398376829-6771-22-git-send-email-mkl@pengutronix.de>
Date: Fri, 25 Apr 2014 00:00:24 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, linux-can@...r.kernel.org,
kernel@...gutronix.de, Thomas Gleixner <tglx@...utronix.de>,
Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 21/26] can: c_can: Speed up tx buffer invalidation
From: Thomas Gleixner <tglx@...utronix.de>
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 <tglx@...utronix.de>
Tested-by: Alexander Stein <alexander.stein@...tec-electronic.com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
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(-)
diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 99d36bf..a2ca820 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -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++;
diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h
index a5f10a0..e7de2b9 100644
--- a/drivers/net/can/c_can/c_can.h
+++ b/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);
--
1.9.0.279.gdc9e3eb
--
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