diff options
Diffstat (limited to 'drivers/net/ipa/ipa_modem.c')
| -rw-r--r-- | drivers/net/ipa/ipa_modem.c | 41 |
1 files changed, 28 insertions, 13 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; |