[PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit()
From: Alex Elder <hidden>
Date: 2021-08-12 19:51:04
Also in:
lkml
Subsystem:
networking drivers, qcom ipa driver, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Alex Elder, Linus Torvalds
We need to ensure the hardware is powered when we transmit a packet. But if it's not, we can't block to wait for it. So asynchronously request power in ipa_start_xmit(), and only proceed if the return value indicates the power state is active. If the hardware is not active, a runtime resume request will have been initiated. In that case, stop the network stack from further transmit attempts until the resume completes. Return NETDEV_TX_BUSY, to retry sending the packet once the queue is restarted. If the power request returns an error (other than -EINPROGRESS, which just means a resume requested elsewhere isn't complete), just drop the packet. Signed-off-by: Alex Elder <redacted> --- drivers/net/ipa/ipa_modem.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ipa/ipa_modem.c b/drivers/net/ipa/ipa_modem.c
index 0a3b034614b61..aa1b483d9f7db 100644
--- a/drivers/net/ipa/ipa_modem.c
+++ b/drivers/net/ipa/ipa_modem.c@@ -106,6 +106,7 @@ static int ipa_start_xmit(struct sk_buff *skb, struct net_device *netdev) struct ipa_endpoint *endpoint; struct ipa *ipa = priv->ipa; u32 skb_len = skb->len; + struct device *dev; int ret; if (!skb_len)
@@ -115,7 +116,31 @@ static int ipa_start_xmit(struct sk_buff *skb, struct net_device *netdev) if (endpoint->data->qmap && skb->protocol != htons(ETH_P_MAP)) goto err_drop_skb; + /* The hardware must be powered for us to transmit */ + dev = &ipa->pdev->dev; + ret = pm_runtime_get(dev); + if (ret < 1) { + /* If a resume won't happen, just drop the packet */ + if (ret < 0 && ret != -EINPROGRESS) { + pm_runtime_put_noidle(dev); + 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. + */ + netif_stop_queue(netdev); + + (void)pm_runtime_put(dev); + + return NETDEV_TX_BUSY; + } + ret = ipa_endpoint_skb_tx(endpoint, skb); + + (void)pm_runtime_put(dev); + if (ret) { if (ret != -E2BIG) return NETDEV_TX_BUSY;
@@ -201,7 +226,10 @@ void ipa_modem_suspend(struct net_device *netdev) * * Re-enable transmit on the modem network device. This is called * in (power management) work queue context, scheduled when resuming - * the modem. + * the modem. We can't enable the queue directly in ipa_modem_resume() + * because transmits restart the instant the queue is awakened; but the + * device power state won't be ACTIVE until *after* ipa_modem_resume() + * returns. */ static void ipa_modem_wake_queue_work(struct work_struct *work) {
--
2.27.0