LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Alex Elder <elder@linaro.org>
To: davem@davemloft.net, kuba@kernel.org
Cc: bjorn.andersson@linaro.org, evgreen@chromium.org,
	cpratapa@codeaurora.org, subashab@codeaurora.org,
	elder@kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit()
Date: Thu, 12 Aug 2021 14:50:33 -0500	[thread overview]
Message-ID: <20210812195035.2816276-5-elder@linaro.org> (raw)
In-Reply-To: <20210812195035.2816276-1-elder@linaro.org>

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 <elder@linaro.org>
---
 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


  parent reply	other threads:[~2021-08-12 19:51 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-12 19:50 [PATCH net-next 0/6] net: ipa: last things before PM conversion Alex Elder
2021-08-12 19:50 ` [PATCH net-next 1/6] net: ipa: enable wakeup in ipa_power_setup() Alex Elder
2021-08-12 19:50 ` [PATCH net-next 2/6] net: ipa: distinguish system from runtime suspend Alex Elder
2021-08-12 19:50 ` [PATCH net-next 3/6] net: ipa: re-enable transmit in PM WQ context Alex Elder
2021-08-14  0:44   ` Jakub Kicinski
2021-08-14  2:32     ` Alex Elder
2021-08-12 19:50 ` Alex Elder [this message]
2021-08-14  0:46   ` [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit() Jakub Kicinski
2021-08-14  2:25     ` Alex Elder
2021-08-16 14:15       ` Jakub Kicinski
2021-08-16 14:20         ` Alex Elder
2021-08-16 17:56           ` Alex Elder
2021-08-16 20:19             ` Jakub Kicinski
2021-08-12 19:50 ` [PATCH net-next 5/6] net: ipa: don't stop TX on suspend Alex Elder
2021-08-12 19:50 ` [PATCH net-next 6/6] net: ipa: don't hold clock reference while netdev open Alex Elder
2021-08-14 13:20 ` [PATCH net-next 0/6] net: ipa: last things before PM conversion patchwork-bot+netdevbpf

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210812195035.2816276-5-elder@linaro.org \
    --to=elder@linaro.org \
    --cc=bjorn.andersson@linaro.org \
    --cc=cpratapa@codeaurora.org \
    --cc=davem@davemloft.net \
    --cc=elder@kernel.org \
    --cc=evgreen@chromium.org \
    --cc=kuba@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=subashab@codeaurora.org \
    --subject='Re: [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).