diff --git a/drivers/net/wireless/wl12xx/debugfs.c b/drivers/net/wireless/wl12xx/debugfs.c index bebfa28a171a..8e75b09723b9 100644 --- a/drivers/net/wireless/wl12xx/debugfs.c +++ b/drivers/net/wireless/wl12xx/debugfs.c @@ -99,7 +99,7 @@ static void wl1271_debugfs_update_stats(struct wl1271 *wl) mutex_lock(&wl->mutex); - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; diff --git a/drivers/net/wireless/wl12xx/io.h b/drivers/net/wireless/wl12xx/io.h index 844b32b170bb..c1aac8292089 100644 --- a/drivers/net/wireless/wl12xx/io.h +++ b/drivers/net/wireless/wl12xx/io.h @@ -168,5 +168,6 @@ void wl1271_unregister_hw(struct wl1271 *wl); int wl1271_init_ieee80211(struct wl1271 *wl); struct ieee80211_hw *wl1271_alloc_hw(void); int wl1271_free_hw(struct wl1271 *wl); +irqreturn_t wl1271_irq(int irq, void *data); #endif diff --git a/drivers/net/wireless/wl12xx/main.c b/drivers/net/wireless/wl12xx/main.c index ba34ac3a440d..f408c5a84cc9 100644 --- a/drivers/net/wireless/wl12xx/main.c +++ b/drivers/net/wireless/wl12xx/main.c @@ -374,7 +374,7 @@ static int wl1271_dev_notify(struct notifier_block *me, unsigned long what, if (!test_bit(WL1271_FLAG_STA_ASSOCIATED, &wl->flags)) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -635,16 +635,39 @@ static void wl1271_fw_status(struct wl1271 *wl, (s64)le32_to_cpu(status->fw_localtime); } -#define WL1271_IRQ_MAX_LOOPS 10 +static void wl1271_flush_deferred_work(struct wl1271 *wl) +{ + struct sk_buff *skb; -static void wl1271_irq_work(struct work_struct *work) + /* Pass all received frames to the network stack */ + while ((skb = skb_dequeue(&wl->deferred_rx_queue))) + ieee80211_rx_ni(wl->hw, skb); + + /* Return sent skbs to the network stack */ + while ((skb = skb_dequeue(&wl->deferred_tx_queue))) + ieee80211_tx_status(wl->hw, skb); +} + +static void wl1271_netstack_work(struct work_struct *work) +{ + struct wl1271 *wl = + container_of(work, struct wl1271, netstack_work); + + do { + wl1271_flush_deferred_work(wl); + } while (skb_queue_len(&wl->deferred_rx_queue)); +} + +#define WL1271_IRQ_MAX_LOOPS 256 + +irqreturn_t wl1271_irq(int irq, void *cookie) { int ret; u32 intr; int loopcount = WL1271_IRQ_MAX_LOOPS; - unsigned long flags; - struct wl1271 *wl = - container_of(work, struct wl1271, irq_work); + struct wl1271 *wl = (struct wl1271 *)cookie; + bool done = false; + unsigned int defer_count; mutex_lock(&wl->mutex); @@ -653,26 +676,27 @@ static void wl1271_irq_work(struct work_struct *work) if (unlikely(wl->state == WL1271_STATE_OFF)) goto out; - ret = wl1271_ps_elp_wakeup(wl, true); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; - spin_lock_irqsave(&wl->wl_lock, flags); - while (test_bit(WL1271_FLAG_IRQ_PENDING, &wl->flags) && loopcount) { - clear_bit(WL1271_FLAG_IRQ_PENDING, &wl->flags); - spin_unlock_irqrestore(&wl->wl_lock, flags); - loopcount--; + while (!done && loopcount--) { + /* + * In order to avoid a race with the hardirq, clear the flag + * before acknowledging the chip. Since the mutex is held, + * wl1271_ps_elp_wakeup cannot be called concurrently. + */ + clear_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags); + smp_mb__after_clear_bit(); wl1271_fw_status(wl, wl->fw_status); intr = le32_to_cpu(wl->fw_status->common.intr); + intr &= WL1271_INTR_MASK; if (!intr) { - wl1271_debug(DEBUG_IRQ, "Zero interrupt received."); - spin_lock_irqsave(&wl->wl_lock, flags); + done = true; continue; } - intr &= WL1271_INTR_MASK; - if (unlikely(intr & WL1271_ACX_INTR_WATCHDOG)) { wl1271_error("watchdog interrupt received! " "starting recovery."); @@ -682,7 +706,7 @@ static void wl1271_irq_work(struct work_struct *work) goto out; } - if (intr & WL1271_ACX_INTR_DATA) { + if (likely(intr & WL1271_ACX_INTR_DATA)) { wl1271_debug(DEBUG_IRQ, "WL1271_ACX_INTR_DATA"); wl1271_rx(wl, &wl->fw_status->common); @@ -701,6 +725,12 @@ static void wl1271_irq_work(struct work_struct *work) if (wl->fw_status->common.tx_results_counter != (wl->tx_results_count & 0xff)) wl1271_tx_complete(wl); + + /* Make sure the deferred queues don't get too long */ + defer_count = skb_queue_len(&wl->deferred_tx_queue) + + skb_queue_len(&wl->deferred_rx_queue); + if (defer_count > WL1271_DEFERRED_QUEUE_LIMIT) + wl1271_flush_deferred_work(wl); } if (intr & WL1271_ACX_INTR_EVENT_A) { @@ -719,21 +749,16 @@ static void wl1271_irq_work(struct work_struct *work) if (intr & WL1271_ACX_INTR_HW_AVAILABLE) wl1271_debug(DEBUG_IRQ, "WL1271_ACX_INTR_HW_AVAILABLE"); - - spin_lock_irqsave(&wl->wl_lock, flags); } - if (test_bit(WL1271_FLAG_IRQ_PENDING, &wl->flags)) - ieee80211_queue_work(wl->hw, &wl->irq_work); - else - clear_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags); - spin_unlock_irqrestore(&wl->wl_lock, flags); - wl1271_ps_elp_sleep(wl); out: mutex_unlock(&wl->mutex); + + return IRQ_HANDLED; } +EXPORT_SYMBOL_GPL(wl1271_irq); static int wl1271_fetch_firmware(struct wl1271 *wl) { @@ -974,7 +999,6 @@ int wl1271_plt_start(struct wl1271 *wl) goto out; irq_disable: - wl1271_disable_interrupts(wl); mutex_unlock(&wl->mutex); /* Unlocking the mutex in the middle of handling is inherently unsafe. In this case we deem it safe to do, @@ -983,7 +1007,9 @@ int wl1271_plt_start(struct wl1271 *wl) work function will not do anything.) Also, any other possible concurrent operations will fail due to the current state, hence the wl1271 struct should be safe. */ - cancel_work_sync(&wl->irq_work); + wl1271_disable_interrupts(wl); + wl1271_flush_deferred_work(wl); + cancel_work_sync(&wl->netstack_work); mutex_lock(&wl->mutex); power_off: wl1271_power_off(wl); @@ -1010,14 +1036,15 @@ int __wl1271_plt_stop(struct wl1271 *wl) goto out; } - wl1271_disable_interrupts(wl); wl1271_power_off(wl); wl->state = WL1271_STATE_OFF; wl->rx_counter = 0; mutex_unlock(&wl->mutex); - cancel_work_sync(&wl->irq_work); + wl1271_disable_interrupts(wl); + wl1271_flush_deferred_work(wl); + cancel_work_sync(&wl->netstack_work); cancel_work_sync(&wl->recovery_work); mutex_lock(&wl->mutex); out: @@ -1169,7 +1196,6 @@ static int wl1271_op_add_interface(struct ieee80211_hw *hw, break; irq_disable: - wl1271_disable_interrupts(wl); mutex_unlock(&wl->mutex); /* Unlocking the mutex in the middle of handling is inherently unsafe. In this case we deem it safe to do, @@ -1178,7 +1204,9 @@ static int wl1271_op_add_interface(struct ieee80211_hw *hw, work function will not do anything.) Also, any other possible concurrent operations will fail due to the current state, hence the wl1271 struct should be safe. */ - cancel_work_sync(&wl->irq_work); + wl1271_disable_interrupts(wl); + wl1271_flush_deferred_work(wl); + cancel_work_sync(&wl->netstack_work); mutex_lock(&wl->mutex); power_off: wl1271_power_off(wl); @@ -1244,12 +1272,12 @@ static void __wl1271_op_remove_interface(struct wl1271 *wl) wl->state = WL1271_STATE_OFF; - wl1271_disable_interrupts(wl); - mutex_unlock(&wl->mutex); + wl1271_disable_interrupts(wl); + wl1271_flush_deferred_work(wl); cancel_delayed_work_sync(&wl->scan_complete_work); - cancel_work_sync(&wl->irq_work); + cancel_work_sync(&wl->netstack_work); cancel_work_sync(&wl->tx_work); cancel_delayed_work_sync(&wl->pspoll_work); cancel_delayed_work_sync(&wl->elp_work); @@ -1525,7 +1553,7 @@ static int wl1271_op_config(struct ieee80211_hw *hw, u32 changed) is_ap = (wl->bss_type == BSS_TYPE_AP_BSS); - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -1681,7 +1709,7 @@ static void wl1271_op_configure_filter(struct ieee80211_hw *hw, if (unlikely(wl->state == WL1271_STATE_OFF)) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -1910,7 +1938,7 @@ static int wl1271_op_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd, goto out_unlock; } - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out_unlock; @@ -2013,7 +2041,7 @@ static int wl1271_op_hw_scan(struct ieee80211_hw *hw, goto out; } - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2039,7 +2067,7 @@ static int wl1271_op_set_frag_threshold(struct ieee80211_hw *hw, u32 value) goto out; } - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2067,7 +2095,7 @@ static int wl1271_op_set_rts_threshold(struct ieee80211_hw *hw, u32 value) goto out; } - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2546,7 +2574,7 @@ static void wl1271_op_bss_info_changed(struct ieee80211_hw *hw, if (unlikely(wl->state == WL1271_STATE_OFF)) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2601,7 +2629,7 @@ static int wl1271_op_conf_tx(struct ieee80211_hw *hw, u16 queue, conf_tid->apsd_conf[0] = 0; conf_tid->apsd_conf[1] = 0; } else { - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2647,7 +2675,7 @@ static u64 wl1271_op_get_tsf(struct ieee80211_hw *hw) if (unlikely(wl->state == WL1271_STATE_OFF)) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2736,7 +2764,7 @@ static int wl1271_op_sta_add(struct ieee80211_hw *hw, if (ret < 0) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out_free_sta; @@ -2779,7 +2807,7 @@ static int wl1271_op_sta_remove(struct ieee80211_hw *hw, if (WARN_ON(!test_bit(id, wl->ap_hlid_map))) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -2812,7 +2840,7 @@ int wl1271_op_ampdu_action(struct ieee80211_hw *hw, struct ieee80211_vif *vif, goto out; } - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -3176,7 +3204,7 @@ static ssize_t wl1271_sysfs_store_bt_coex_state(struct device *dev, if (wl->state == WL1271_STATE_OFF) goto out; - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out; @@ -3376,9 +3404,12 @@ struct ieee80211_hw *wl1271_alloc_hw(void) for (j = 0; j < AP_MAX_LINKS; j++) skb_queue_head_init(&wl->links[j].tx_queue[i]); + skb_queue_head_init(&wl->deferred_rx_queue); + skb_queue_head_init(&wl->deferred_tx_queue); + INIT_DELAYED_WORK(&wl->elp_work, wl1271_elp_work); INIT_DELAYED_WORK(&wl->pspoll_work, wl1271_pspoll_work); - INIT_WORK(&wl->irq_work, wl1271_irq_work); + INIT_WORK(&wl->netstack_work, wl1271_netstack_work); INIT_WORK(&wl->tx_work, wl1271_tx_work); INIT_WORK(&wl->recovery_work, wl1271_recovery_work); INIT_DELAYED_WORK(&wl->scan_complete_work, wl1271_scan_complete_work); diff --git a/drivers/net/wireless/wl12xx/ps.c b/drivers/net/wireless/wl12xx/ps.c index 5c347b1bd17f..971f13e792da 100644 --- a/drivers/net/wireless/wl12xx/ps.c +++ b/drivers/net/wireless/wl12xx/ps.c @@ -69,7 +69,7 @@ void wl1271_ps_elp_sleep(struct wl1271 *wl) } } -int wl1271_ps_elp_wakeup(struct wl1271 *wl, bool chip_awake) +int wl1271_ps_elp_wakeup(struct wl1271 *wl) { DECLARE_COMPLETION_ONSTACK(compl); unsigned long flags; @@ -87,7 +87,7 @@ int wl1271_ps_elp_wakeup(struct wl1271 *wl, bool chip_awake) * the completion variable in one entity. */ spin_lock_irqsave(&wl->wl_lock, flags); - if (work_pending(&wl->irq_work) || chip_awake) + if (test_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags)) pending = true; else wl->elp_compl = &compl; @@ -149,7 +149,7 @@ int wl1271_ps_set_mode(struct wl1271 *wl, enum wl1271_cmd_ps_mode mode, case STATION_ACTIVE_MODE: default: wl1271_debug(DEBUG_PSM, "leaving psm"); - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) return ret; diff --git a/drivers/net/wireless/wl12xx/ps.h b/drivers/net/wireless/wl12xx/ps.h index fc1f4c193593..c41bd0a711bc 100644 --- a/drivers/net/wireless/wl12xx/ps.h +++ b/drivers/net/wireless/wl12xx/ps.h @@ -30,7 +30,7 @@ int wl1271_ps_set_mode(struct wl1271 *wl, enum wl1271_cmd_ps_mode mode, u32 rates, bool send); void wl1271_ps_elp_sleep(struct wl1271 *wl); -int wl1271_ps_elp_wakeup(struct wl1271 *wl, bool chip_awake); +int wl1271_ps_elp_wakeup(struct wl1271 *wl); void wl1271_elp_work(struct work_struct *work); void wl1271_ps_link_start(struct wl1271 *wl, u8 hlid, bool clean_queues); void wl1271_ps_link_end(struct wl1271 *wl, u8 hlid); diff --git a/drivers/net/wireless/wl12xx/rx.c b/drivers/net/wireless/wl12xx/rx.c index 4e7a3b311321..919b59f00301 100644 --- a/drivers/net/wireless/wl12xx/rx.c +++ b/drivers/net/wireless/wl12xx/rx.c @@ -129,7 +129,8 @@ static int wl1271_rx_handle_data(struct wl1271 *wl, u8 *data, u32 length) skb_trim(skb, skb->len - desc->pad_len); - ieee80211_rx_ni(wl->hw, skb); + skb_queue_tail(&wl->deferred_rx_queue, skb); + ieee80211_queue_work(wl->hw, &wl->netstack_work); return 0; } diff --git a/drivers/net/wireless/wl12xx/sdio.c b/drivers/net/wireless/wl12xx/sdio.c index 61fdc9e981bd..b66abb5ebcf3 100644 --- a/drivers/net/wireless/wl12xx/sdio.c +++ b/drivers/net/wireless/wl12xx/sdio.c @@ -61,7 +61,7 @@ static struct device *wl1271_sdio_wl_to_dev(struct wl1271 *wl) return &(wl_to_func(wl)->dev); } -static irqreturn_t wl1271_irq(int irq, void *cookie) +static irqreturn_t wl1271_hardirq(int irq, void *cookie) { struct wl1271 *wl = cookie; unsigned long flags; @@ -70,17 +70,14 @@ static irqreturn_t wl1271_irq(int irq, void *cookie) /* complete the ELP completion */ spin_lock_irqsave(&wl->wl_lock, flags); + set_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags); if (wl->elp_compl) { complete(wl->elp_compl); wl->elp_compl = NULL; } - - if (!test_and_set_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags)) - ieee80211_queue_work(wl->hw, &wl->irq_work); - set_bit(WL1271_FLAG_IRQ_PENDING, &wl->flags); spin_unlock_irqrestore(&wl->wl_lock, flags); - return IRQ_HANDLED; + return IRQ_WAKE_THREAD; } static void wl1271_sdio_disable_interrupts(struct wl1271 *wl) @@ -243,14 +240,14 @@ static int __devinit wl1271_probe(struct sdio_func *func, wl->irq = wlan_data->irq; wl->ref_clock = wlan_data->board_ref_clock; - ret = request_irq(wl->irq, wl1271_irq, 0, DRIVER_NAME, wl); + ret = request_threaded_irq(wl->irq, wl1271_hardirq, wl1271_irq, + IRQF_TRIGGER_RISING, + DRIVER_NAME, wl); if (ret < 0) { wl1271_error("request_irq() failed: %d", ret); goto out_free; } - set_irq_type(wl->irq, IRQ_TYPE_EDGE_RISING); - disable_irq(wl->irq); ret = wl1271_init_ieee80211(wl); @@ -273,7 +270,6 @@ static int __devinit wl1271_probe(struct sdio_func *func, out_irq: free_irq(wl->irq, wl); - out_free: wl1271_free_hw(wl); diff --git a/drivers/net/wireless/wl12xx/spi.c b/drivers/net/wireless/wl12xx/spi.c index 0132dad756c4..df5a00f103ea 100644 --- a/drivers/net/wireless/wl12xx/spi.c +++ b/drivers/net/wireless/wl12xx/spi.c @@ -320,28 +320,23 @@ static void wl1271_spi_raw_write(struct wl1271 *wl, int addr, void *buf, spi_sync(wl_to_spi(wl), &m); } -static irqreturn_t wl1271_irq(int irq, void *cookie) +static irqreturn_t wl1271_hardirq(int irq, void *cookie) { - struct wl1271 *wl; + struct wl1271 *wl = cookie; unsigned long flags; wl1271_debug(DEBUG_IRQ, "IRQ"); - wl = cookie; - /* complete the ELP completion */ spin_lock_irqsave(&wl->wl_lock, flags); + set_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags); if (wl->elp_compl) { complete(wl->elp_compl); wl->elp_compl = NULL; } - - if (!test_and_set_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags)) - ieee80211_queue_work(wl->hw, &wl->irq_work); - set_bit(WL1271_FLAG_IRQ_PENDING, &wl->flags); spin_unlock_irqrestore(&wl->wl_lock, flags); - return IRQ_HANDLED; + return IRQ_WAKE_THREAD; } static int wl1271_spi_set_power(struct wl1271 *wl, bool enable) @@ -413,14 +408,14 @@ static int __devinit wl1271_probe(struct spi_device *spi) goto out_free; } - ret = request_irq(wl->irq, wl1271_irq, 0, DRIVER_NAME, wl); + ret = request_threaded_irq(wl->irq, wl1271_hardirq, wl1271_irq, + IRQF_TRIGGER_RISING, + DRIVER_NAME, wl); if (ret < 0) { wl1271_error("request_irq() failed: %d", ret); goto out_free; } - set_irq_type(wl->irq, IRQ_TYPE_EDGE_RISING); - disable_irq(wl->irq); ret = wl1271_init_ieee80211(wl); diff --git a/drivers/net/wireless/wl12xx/tx.c b/drivers/net/wireless/wl12xx/tx.c index 455954edf83e..5e9ef7d53e7e 100644 --- a/drivers/net/wireless/wl12xx/tx.c +++ b/drivers/net/wireless/wl12xx/tx.c @@ -464,7 +464,7 @@ void wl1271_tx_work_locked(struct wl1271 *wl) while ((skb = wl1271_skb_dequeue(wl))) { if (!woken_up) { - ret = wl1271_ps_elp_wakeup(wl, false); + ret = wl1271_ps_elp_wakeup(wl); if (ret < 0) goto out_ack; woken_up = true; @@ -589,7 +589,8 @@ static void wl1271_tx_complete_packet(struct wl1271 *wl, result->rate_class_index, result->status); /* return the packet to the stack */ - ieee80211_tx_status(wl->hw, skb); + skb_queue_tail(&wl->deferred_tx_queue, skb); + ieee80211_queue_work(wl->hw, &wl->netstack_work); wl1271_free_tx_id(wl, result->id); } diff --git a/drivers/net/wireless/wl12xx/wl12xx.h b/drivers/net/wireless/wl12xx/wl12xx.h index ea1eee7895cf..e395c0c4ebbd 100644 --- a/drivers/net/wireless/wl12xx/wl12xx.h +++ b/drivers/net/wireless/wl12xx/wl12xx.h @@ -320,7 +320,6 @@ enum wl12xx_flags { WL1271_FLAG_IN_ELP, WL1271_FLAG_PSM, WL1271_FLAG_PSM_REQUESTED, - WL1271_FLAG_IRQ_PENDING, WL1271_FLAG_IRQ_RUNNING, WL1271_FLAG_IDLE, WL1271_FLAG_IDLE_REQUESTED, @@ -404,6 +403,12 @@ struct wl1271 { struct sk_buff_head tx_queue[NUM_TX_QUEUES]; int tx_queue_count; + /* Frames received, not handled yet by mac80211 */ + struct sk_buff_head deferred_rx_queue; + + /* Frames sent, not returned yet to mac80211 */ + struct sk_buff_head deferred_tx_queue; + struct work_struct tx_work; /* Pending TX frames */ @@ -424,8 +429,8 @@ struct wl1271 { /* Intermediate buffer, used for packet aggregation */ u8 *aggr_buf; - /* The target interrupt mask */ - struct work_struct irq_work; + /* Network stack work */ + struct work_struct netstack_work; /* Hardware recovery work */ struct work_struct recovery_work; @@ -556,6 +561,8 @@ int wl1271_plt_stop(struct wl1271 *wl); #define WL1271_TX_QUEUE_LOW_WATERMARK 10 #define WL1271_TX_QUEUE_HIGH_WATERMARK 25 +#define WL1271_DEFERRED_QUEUE_LIMIT 64 + /* WL1271 needs a 200ms sleep after power on, and a 20ms sleep before power on in case is has been shut down shortly before */ #define WL1271_PRE_POWER_ON_SLEEP 20 /* in milliseconds */