diff options
Diffstat (limited to 'drivers/net/ipa')
| -rw-r--r-- | drivers/net/ipa/ipa_modem.c | 41 | ||||
| -rw-r--r-- | drivers/net/ipa/ipa_power.c | 44 |
2 files changed, 54 insertions, 31 deletions
diff --git a/drivers/net/ipa/ipa_modem.c b/drivers/net/ipa/ipa_modem.c index a6f6cd149c1b..c7a0b167c432 100644 --- a/drivers/net/ipa/ipa_modem.c +++ b/drivers/net/ipa/ipa_modem.c @@ -110,13 +110,16 @@ out_power_put: return 0; } -/** ipa_start_xmit() - Transmits an skb. - * @skb: skb to be transmitted - * @dev: network device +/** ipa_start_xmit() - Transmit an skb + * @skb: Socket buffer to be transmitted + * @netdev: Network device * - * Return codes: - * NETDEV_TX_OK: Success - * NETDEV_TX_BUSY: Error while transmitting the skb. Try again later + * Return: NETDEV_TX_OK if successful (or dropped), NETDEV_TX_BUSY otherwise + + * Normally NETDEV_TX_OK indicates the buffer was successfully transmitted. + * If the buffer has an unexpected protocol or its size is out of range it + * is quietly dropped, returning NETDEV_TX_OK. NETDEV_TX_BUSY indicates + * the buffer cannot be sent at this time and should retried later. */ static netdev_tx_t ipa_start_xmit(struct sk_buff *skb, struct net_device *netdev) @@ -136,7 +139,25 @@ ipa_start_xmit(struct sk_buff *skb, struct net_device *netdev) if (endpoint->config.qmap && skb->protocol != htons(ETH_P_MAP)) goto err_drop_skb; - /* The hardware must be powered for us to transmit */ + /* The hardware must be powered for us to transmit, so if we're not + * ready we want the network stack to stop queueing until power is + * ACTIVE. Once runtime resume has completed, we inform the network + * stack it's OK to try transmitting again. + * + * We learn from pm_runtime_get() whether the hardware is powered. + * If it was not, powering up is either started or already underway. + * And in that case we want to disable queueing, expecting it to be + * re-enabled once power is ACTIVE. But runtime PM and network + * transmit run concurrently, and if we're not careful the requests + * to stop and start queueing could occur in the wrong order. + * + * For that reason we *always* stop queueing here, *before* the call + * to pm_runtime_get(). If we determine here that power is ACTIVE, + * we restart queueing before transmitting the SKB. Otherwise + * queueing will eventually be enabled after resume completes. + */ + ipa_power_modem_queue_stop(ipa); + dev = &ipa->pdev->dev; ret = pm_runtime_get(dev); if (ret < 1) { @@ -147,12 +168,6 @@ ipa_start_xmit(struct sk_buff *skb, struct net_device *netdev) goto err_drop_skb; } - /* No power (yet). Stop the network stack from transmitting - * until we're resumed; ipa_modem_resume() arranges for the - * TX queue to be started again. - */ - ipa_power_modem_queue_stop(ipa); - pm_runtime_put_noidle(dev); return NETDEV_TX_BUSY; diff --git a/drivers/net/ipa/ipa_power.c b/drivers/net/ipa/ipa_power.c index e223886123ce..f1802448ff44 100644 --- a/drivers/net/ipa/ipa_power.c +++ b/drivers/net/ipa/ipa_power.c @@ -233,28 +233,32 @@ void ipa_power_suspend_handler(struct ipa *ipa, enum ipa_irq_id irq_id) ipa_interrupt_suspend_clear_all(ipa->interrupt); } -/* The next few functions coordinate stopping and starting the modem +/* The next few functions are used when stopping and starting the modem * network device transmit queue. * - * Transmit can be running concurrent with power resume, and there's a - * chance the resume completes before the transmit path stops the queue, - * leaving the queue in a stopped state. The next two functions are used - * to avoid this: ipa_power_modem_queue_stop() is used by ipa_start_xmit() - * to conditionally stop the TX queue; and ipa_power_modem_queue_start() - * is used by ipa_runtime_resume() to conditionally restart it. + * Transmit can run concurrent with power resume. When transmitting, + * we disable further transmits until we can determine whether power + * is ACTIVE. If it is, future transmits are re-enabled and the buffer + * gets sent (or dropped). If power is not ACTIVE, it will eventually + * be, and transmits stay disabled until after it is. * - * Two flags and a spinlock are used. If the queue is stopped, the STOPPED - * power flag is set. And if the queue is started, the STARTED flag is set. - * The queue is only started on resume if the STOPPED flag is set. And the - * queue is only started in ipa_start_xmit() if the STARTED flag is *not* - * set. As a result, the queue remains operational if the two activites - * happen concurrently regardless of the order they complete. The spinlock - * ensures the flag and TX queue operations are done atomically. + * Two flags and a spinlock are used when managing this. If the queue + * is stopped, the STOPPED power flag is set. And if the queue is + * started, the STARTED flag is set. * * The first function stops the modem netdev transmit queue, but only if - * the STARTED flag is *not* set. That flag is cleared if it was set. - * If the queue is stopped, the STOPPED flag is set. This is called only - * from the power ->runtime_resume operation. + * the STARTED flag is *not* set. This previously avoided a race where + * the TX path stops further transmits after power has become ACTIVE. + * The STARTED flag is cleared by this function. + * + * The second function starts the transmit queue, but only if the + * STOPPED flag is set. This avoids enabling transmits repeatedly + * immediately after power has become ACTIVE (not really a big deal). + * If the STOPPED flag was set, it is cleared and the STARTED flag + * is set by this function. + * + * The third function enables transmits again and clears the STARTED + * flag in case it was set, to return it to initial state. */ void ipa_power_modem_queue_stop(struct ipa *ipa) { @@ -291,9 +295,13 @@ void ipa_power_modem_queue_wake(struct ipa *ipa) spin_unlock_irqrestore(&power->spinlock, flags); } -/* This function clears the STARTED flag once the TX queue is operating */ +/* This function is run after power has become ACTIVE. It enables transmits + * again clears the STARTED flag to indicate the TX queue is operating and + * can be stopped again if necessary. + */ void ipa_power_modem_queue_active(struct ipa *ipa) { + netif_wake_queue(ipa->modem_netdev); clear_bit(IPA_POWER_FLAG_STARTED, ipa->power->flags); } |