From c84ff1d6dff38058a5bd20cb633d13a0f685788a Mon Sep 17 00:00:00 2001 From: Alexey Orishko Date: Wed, 14 Mar 2012 11:26:10 +0000 Subject: [PATCH] cdc_ncm: reduce driver latency in the data path MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Tested-by: Dmitry Tarnyagin Signed-off-by: Alexey Orishko Signed-off-by: David S. Miller --- drivers/net/usb/cdc_ncm.c | 94 +++++++++++++++++++++------------------ 1 file changed, 51 insertions(+), 43 deletions(-) diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index 81f86b8ea55..a8e2a62c295 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 * Original author: Hans Petter Selasky * @@ -47,13 +47,12 @@ #include #include #include -#include -#include +#include #include #include #include -#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: -- 2.41.0