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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@stericsson.com> Tested-by: Dmitry Tarnyagin <Dmitry.Tarnyagin@stericsson.com> Signed-off-by: Alexey Orishko <alexey.orishko@stericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexey Orishko
David S. Miller
parent
a9e0aca4b3
commit
c84ff1d6df
@ -1,7 +1,7 @@
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/*
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* cdc_ncm.c
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*
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* Copyright (C) ST-Ericsson 2010-2011
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* Copyright (C) ST-Ericsson 2010-2012
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* Contact: Alexey Orishko <alexey.orishko@stericsson.com>
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* Original author: Hans Petter Selasky <hans.petter.selasky@stericsson.com>
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*
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@ -47,13 +47,12 @@
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#include <linux/mii.h>
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#include <linux/crc32.h>
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#include <linux/usb.h>
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#include <linux/timer.h>
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#include <linux/spinlock.h>
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#include <linux/hrtimer.h>
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#include <linux/atomic.h>
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#include <linux/usb/usbnet.h>
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#include <linux/usb/cdc.h>
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#define DRIVER_VERSION "04-Aug-2011"
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#define DRIVER_VERSION "14-Mar-2012"
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/* CDC NCM subclass 3.2.1 */
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#define USB_CDC_NCM_NDP16_LENGTH_MIN 0x10
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@ -81,6 +80,8 @@
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/* Restart the timer, if amount of datagrams is less than given value */
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#define CDC_NCM_RESTART_TIMER_DATAGRAM_CNT 3
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#define CDC_NCM_TIMER_PENDING_CNT 2
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#define CDC_NCM_TIMER_INTERVAL (400UL * NSEC_PER_USEC)
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/* The following macro defines the minimum header space */
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#define CDC_NCM_MIN_HDR_SIZE \
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@ -97,7 +98,8 @@ struct cdc_ncm_ctx {
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struct cdc_ncm_data rx_ncm;
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struct cdc_ncm_data tx_ncm;
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struct usb_cdc_ncm_ntb_parameters ncm_parm;
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struct timer_list tx_timer;
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struct hrtimer tx_timer;
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struct tasklet_struct bh;
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const struct usb_cdc_ncm_desc *func_desc;
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const struct usb_cdc_header_desc *header_desc;
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@ -117,6 +119,7 @@ struct cdc_ncm_ctx {
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struct sk_buff *tx_rem_skb;
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spinlock_t mtx;
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atomic_t stop;
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u32 tx_timer_pending;
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u32 tx_curr_offset;
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@ -135,7 +138,9 @@ struct cdc_ncm_ctx {
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u16 connected;
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};
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static void cdc_ncm_tx_timeout(unsigned long arg);
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static void cdc_ncm_txpath_bh(unsigned long param);
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static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
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static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
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static const struct driver_info cdc_ncm_info;
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static struct usb_driver cdc_ncm_driver;
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static const struct ethtool_ops cdc_ncm_ethtool_ops;
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@ -441,8 +446,6 @@ static void cdc_ncm_free(struct cdc_ncm_ctx *ctx)
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if (ctx == NULL)
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return;
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del_timer_sync(&ctx->tx_timer);
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if (ctx->tx_rem_skb != NULL) {
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dev_kfree_skb_any(ctx->tx_rem_skb);
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ctx->tx_rem_skb = NULL;
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@ -469,7 +472,11 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
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if (ctx == NULL)
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return -ENODEV;
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init_timer(&ctx->tx_timer);
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hrtimer_init(&ctx->tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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ctx->tx_timer.function = &cdc_ncm_tx_timer_cb;
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ctx->bh.data = (unsigned long)ctx;
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ctx->bh.func = cdc_ncm_txpath_bh;
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atomic_set(&ctx->stop, 0);
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spin_lock_init(&ctx->mtx);
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ctx->netdev = dev->net;
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@ -617,6 +624,13 @@ static void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf)
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if (ctx == NULL)
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return; /* no setup */
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atomic_set(&ctx->stop, 1);
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if (hrtimer_active(&ctx->tx_timer))
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hrtimer_cancel(&ctx->tx_timer);
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tasklet_kill(&ctx->bh);
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/* disconnect master --> disconnect slave */
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if (intf == ctx->control && ctx->data) {
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usb_set_intfdata(ctx->data, NULL);
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@ -787,7 +801,7 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
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ctx->tx_curr_last_offset = last_offset;
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/* set the pending count */
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if (n < CDC_NCM_RESTART_TIMER_DATAGRAM_CNT)
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ctx->tx_timer_pending = 2;
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ctx->tx_timer_pending = CDC_NCM_TIMER_PENDING_CNT;
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goto exit_no_skb;
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} else {
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@ -867,44 +881,49 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
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/* return skb */
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ctx->tx_curr_skb = NULL;
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ctx->netdev->stats.tx_packets += ctx->tx_curr_frame_num;
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return skb_out;
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exit_no_skb:
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/* Start timer, if there is a remaining skb */
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if (ctx->tx_curr_skb != NULL)
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cdc_ncm_tx_timeout_start(ctx);
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return NULL;
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}
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static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx)
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{
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/* start timer, if not already started */
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if (timer_pending(&ctx->tx_timer) == 0) {
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ctx->tx_timer.function = &cdc_ncm_tx_timeout;
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ctx->tx_timer.data = (unsigned long)ctx;
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ctx->tx_timer.expires = jiffies + ((HZ + 999) / 1000);
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add_timer(&ctx->tx_timer);
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}
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if (!(hrtimer_active(&ctx->tx_timer) || atomic_read(&ctx->stop)))
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hrtimer_start(&ctx->tx_timer,
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ktime_set(0, CDC_NCM_TIMER_INTERVAL),
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HRTIMER_MODE_REL);
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}
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static void cdc_ncm_tx_timeout(unsigned long arg)
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static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *timer)
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{
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struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)arg;
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u8 restart;
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struct cdc_ncm_ctx *ctx =
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container_of(timer, struct cdc_ncm_ctx, tx_timer);
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spin_lock(&ctx->mtx);
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if (!atomic_read(&ctx->stop))
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tasklet_schedule(&ctx->bh);
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return HRTIMER_NORESTART;
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}
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static void cdc_ncm_txpath_bh(unsigned long param)
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{
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struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)param;
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spin_lock_bh(&ctx->mtx);
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if (ctx->tx_timer_pending != 0) {
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ctx->tx_timer_pending--;
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restart = 1;
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} else {
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restart = 0;
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}
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spin_unlock(&ctx->mtx);
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if (restart) {
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spin_lock(&ctx->mtx);
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cdc_ncm_tx_timeout_start(ctx);
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spin_unlock(&ctx->mtx);
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spin_unlock_bh(&ctx->mtx);
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} else if (ctx->netdev != NULL) {
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spin_unlock_bh(&ctx->mtx);
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netif_tx_lock_bh(ctx->netdev);
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usbnet_start_xmit(NULL, ctx->netdev);
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netif_tx_unlock_bh(ctx->netdev);
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}
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}
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@ -913,7 +932,6 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
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{
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struct sk_buff *skb_out;
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struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
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u8 need_timer = 0;
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/*
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* The Ethernet API we are using does not support transmitting
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@ -925,19 +943,9 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
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if (ctx == NULL)
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goto error;
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spin_lock(&ctx->mtx);
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spin_lock_bh(&ctx->mtx);
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skb_out = cdc_ncm_fill_tx_frame(ctx, skb);
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if (ctx->tx_curr_skb != NULL)
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need_timer = 1;
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/* Start timer, if there is a remaining skb */
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if (need_timer)
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cdc_ncm_tx_timeout_start(ctx);
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if (skb_out)
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dev->net->stats.tx_packets += ctx->tx_curr_frame_num;
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spin_unlock(&ctx->mtx);
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spin_unlock_bh(&ctx->mtx);
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return skb_out;
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error:
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