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Date: Wed, 14 Mar 2012 22:26:10 +0100
From: Alexey Orishko <alexey.orishko@...il.com>
To: netdev@...r.kernel.org, davem@...emloft.net, oliver@...kum.org
Cc: linux-usb@...r.kernel.org, gregkh@...uxfoundation.org,
Alexey Orishko <alexey.orishko@...ricsson.com>
Subject: [PATCH net-next 1/4] cdc_ncm: reduce driver latency in the data path
Changes:
- use high resolution timer
latency became approx. 10-15 times less than before
- use taklet for sending remaining data in tx path
Tested on Intel/ARM.
Reviewed-by: Sjur Brændeland <sjur.brandeland@...ricsson.com>
Tested-by: Dmitry Tarnyagin <Dmitry.Tarnyagin@...ricsson.com>
Signed-off-by: Alexey Orishko <alexey.orishko@...ricsson.com>
---
drivers/net/usb/cdc_ncm.c | 94 ++++++++++++++++++++++++--------------------
1 files changed, 51 insertions(+), 43 deletions(-)
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 81f86b8..a8e2a62 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1,7 +1,7 @@
/*
* cdc_ncm.c
*
- * Copyright (C) ST-Ericsson 2010-2011
+ * Copyright (C) ST-Ericsson 2010-2012
* Contact: Alexey Orishko <alexey.orishko@...ricsson.com>
* Original author: Hans Petter Selasky <hans.petter.selasky@...ricsson.com>
*
@@ -47,13 +47,12 @@
#include <linux/mii.h>
#include <linux/crc32.h>
#include <linux/usb.h>
-#include <linux/timer.h>
-#include <linux/spinlock.h>
+#include <linux/hrtimer.h>
#include <linux/atomic.h>
#include <linux/usb/usbnet.h>
#include <linux/usb/cdc.h>
-#define DRIVER_VERSION "04-Aug-2011"
+#define DRIVER_VERSION "14-Mar-2012"
/* CDC NCM subclass 3.2.1 */
#define USB_CDC_NCM_NDP16_LENGTH_MIN 0x10
@@ -81,6 +80,8 @@
/* Restart the timer, if amount of datagrams is less than given value */
#define CDC_NCM_RESTART_TIMER_DATAGRAM_CNT 3
+#define CDC_NCM_TIMER_PENDING_CNT 2
+#define CDC_NCM_TIMER_INTERVAL (400UL * NSEC_PER_USEC)
/* The following macro defines the minimum header space */
#define CDC_NCM_MIN_HDR_SIZE \
@@ -97,7 +98,8 @@ struct cdc_ncm_ctx {
struct cdc_ncm_data rx_ncm;
struct cdc_ncm_data tx_ncm;
struct usb_cdc_ncm_ntb_parameters ncm_parm;
- struct timer_list tx_timer;
+ struct hrtimer tx_timer;
+ struct tasklet_struct bh;
const struct usb_cdc_ncm_desc *func_desc;
const struct usb_cdc_header_desc *header_desc;
@@ -117,6 +119,7 @@ struct cdc_ncm_ctx {
struct sk_buff *tx_rem_skb;
spinlock_t mtx;
+ atomic_t stop;
u32 tx_timer_pending;
u32 tx_curr_offset;
@@ -135,7 +138,9 @@ struct cdc_ncm_ctx {
u16 connected;
};
-static void cdc_ncm_tx_timeout(unsigned long arg);
+static void cdc_ncm_txpath_bh(unsigned long param);
+static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
+static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
static const struct driver_info cdc_ncm_info;
static struct usb_driver cdc_ncm_driver;
static const struct ethtool_ops cdc_ncm_ethtool_ops;
@@ -441,8 +446,6 @@ static void cdc_ncm_free(struct cdc_ncm_ctx *ctx)
if (ctx == NULL)
return;
- del_timer_sync(&ctx->tx_timer);
-
if (ctx->tx_rem_skb != NULL) {
dev_kfree_skb_any(ctx->tx_rem_skb);
ctx->tx_rem_skb = NULL;
@@ -469,7 +472,11 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
if (ctx == NULL)
return -ENODEV;
- init_timer(&ctx->tx_timer);
+ hrtimer_init(&ctx->tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ ctx->tx_timer.function = &cdc_ncm_tx_timer_cb;
+ ctx->bh.data = (unsigned long)ctx;
+ ctx->bh.func = cdc_ncm_txpath_bh;
+ atomic_set(&ctx->stop, 0);
spin_lock_init(&ctx->mtx);
ctx->netdev = dev->net;
@@ -617,6 +624,13 @@ static void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf)
if (ctx == NULL)
return; /* no setup */
+ atomic_set(&ctx->stop, 1);
+
+ if (hrtimer_active(&ctx->tx_timer))
+ hrtimer_cancel(&ctx->tx_timer);
+
+ tasklet_kill(&ctx->bh);
+
/* disconnect master --> disconnect slave */
if (intf == ctx->control && ctx->data) {
usb_set_intfdata(ctx->data, NULL);
@@ -787,7 +801,7 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
ctx->tx_curr_last_offset = last_offset;
/* set the pending count */
if (n < CDC_NCM_RESTART_TIMER_DATAGRAM_CNT)
- ctx->tx_timer_pending = 2;
+ ctx->tx_timer_pending = CDC_NCM_TIMER_PENDING_CNT;
goto exit_no_skb;
} else {
@@ -867,44 +881,49 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
/* return skb */
ctx->tx_curr_skb = NULL;
+ ctx->netdev->stats.tx_packets += ctx->tx_curr_frame_num;
return skb_out;
exit_no_skb:
+ /* Start timer, if there is a remaining skb */
+ if (ctx->tx_curr_skb != NULL)
+ cdc_ncm_tx_timeout_start(ctx);
return NULL;
}
static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx)
{
/* start timer, if not already started */
- if (timer_pending(&ctx->tx_timer) == 0) {
- ctx->tx_timer.function = &cdc_ncm_tx_timeout;
- ctx->tx_timer.data = (unsigned long)ctx;
- ctx->tx_timer.expires = jiffies + ((HZ + 999) / 1000);
- add_timer(&ctx->tx_timer);
- }
+ if (!(hrtimer_active(&ctx->tx_timer) || atomic_read(&ctx->stop)))
+ hrtimer_start(&ctx->tx_timer,
+ ktime_set(0, CDC_NCM_TIMER_INTERVAL),
+ HRTIMER_MODE_REL);
}
-static void cdc_ncm_tx_timeout(unsigned long arg)
+static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *timer)
{
- struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)arg;
- u8 restart;
+ struct cdc_ncm_ctx *ctx =
+ container_of(timer, struct cdc_ncm_ctx, tx_timer);
- spin_lock(&ctx->mtx);
- if (ctx->tx_timer_pending != 0) {
- ctx->tx_timer_pending--;
- restart = 1;
- } else {
- restart = 0;
- }
+ if (!atomic_read(&ctx->stop))
+ tasklet_schedule(&ctx->bh);
+ return HRTIMER_NORESTART;
+}
- spin_unlock(&ctx->mtx);
+static void cdc_ncm_txpath_bh(unsigned long param)
+{
+ struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)param;
- if (restart) {
- spin_lock(&ctx->mtx);
+ spin_lock_bh(&ctx->mtx);
+ if (ctx->tx_timer_pending != 0) {
+ ctx->tx_timer_pending--;
cdc_ncm_tx_timeout_start(ctx);
- spin_unlock(&ctx->mtx);
+ spin_unlock_bh(&ctx->mtx);
} else if (ctx->netdev != NULL) {
+ spin_unlock_bh(&ctx->mtx);
+ netif_tx_lock_bh(ctx->netdev);
usbnet_start_xmit(NULL, ctx->netdev);
+ netif_tx_unlock_bh(ctx->netdev);
}
}
@@ -913,7 +932,6 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
{
struct sk_buff *skb_out;
struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
- u8 need_timer = 0;
/*
* The Ethernet API we are using does not support transmitting
@@ -925,19 +943,9 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
if (ctx == NULL)
goto error;
- spin_lock(&ctx->mtx);
+ spin_lock_bh(&ctx->mtx);
skb_out = cdc_ncm_fill_tx_frame(ctx, skb);
- if (ctx->tx_curr_skb != NULL)
- need_timer = 1;
-
- /* Start timer, if there is a remaining skb */
- if (need_timer)
- cdc_ncm_tx_timeout_start(ctx);
-
- if (skb_out)
- dev->net->stats.tx_packets += ctx->tx_curr_frame_num;
-
- spin_unlock(&ctx->mtx);
+ spin_unlock_bh(&ctx->mtx);
return skb_out;
error:
--
1.7.4.1
--
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