netdev - [PATCH net-next 9/9] net: ipa: don't disable NAPI in suspend

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Date:   Fri, 29 Jan 2021 14:20:19 -0600
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     elder@...nel.org, evgreen@...omium.org, bjorn.andersson@...aro.org,
        cpratapa@...eaurora.org, subashab@...eaurora.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 9/9] net: ipa: don't disable NAPI in suspend

The channel stop and suspend paths both call __gsi_channel_stop(),
which quiesces channel activity, disables NAPI, and (on other than
SDM845) stops the channel.  Similarly, the start and resume paths
share __gsi_channel_start(), which starts the channel and re-enables
NAPI again.

Disabling NAPI should be done when stopping a channel, but this
should *not* be done when suspending.  It's not necessary in the
suspend path anyway, because the stopped channel (or suspended
endpoint on SDM845) will not cause interrupts to schedule NAPI,
and gsi_channel_trans_quiesce() won't return until there are no
more transactions to process in the NAPI polling loop.

Instead, enable NAPI in gsi_channel_start(), when the completion
interrupt is first enabled.  Disable it again in gsi_channel_stop(),
when finally disabling the interrupt.

Add a call to napi_synchronize() to __gsi_channel_stop(), to ensure
NAPI polling is done before moving on.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/gsi.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 217ca21bfe043..afc5c9ede01af 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -876,15 +876,15 @@ static int __gsi_channel_start(struct gsi_channel *channel, bool start)
 	struct gsi *gsi = channel->gsi;
 	int ret;
 
+	if (!start)
+		return 0;
+
 	mutex_lock(&gsi->mutex);
 
-	ret = start ? gsi_channel_start_command(channel) : 0;
+	ret = gsi_channel_start_command(channel);
 
 	mutex_unlock(&gsi->mutex);
 
-	if (!ret)
-		napi_enable(&channel->napi);
-
 	return ret;
 }
 
@@ -894,12 +894,16 @@ int gsi_channel_start(struct gsi *gsi, u32 channel_id)
 	struct gsi_channel *channel = &gsi->channel[channel_id];
 	int ret;
 
-	/* Enable the completion interrupt */
+	/* Enable NAPI and the completion interrupt */
+	napi_enable(&channel->napi);
 	gsi_irq_ieob_enable_one(gsi, channel->evt_ring_id);
 
 	ret = __gsi_channel_start(channel, true);
-	if (ret)
-		gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
+	if (!ret)
+		return 0;
+
+	gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
+	napi_disable(&channel->napi);
 
 	return ret;
 }
@@ -928,13 +932,13 @@ static int __gsi_channel_stop(struct gsi_channel *channel, bool stop)
 {
 	int ret;
 
+	/* Wait for any underway transactions to complete before stopping. */
 	gsi_channel_trans_quiesce(channel);
-	napi_disable(&channel->napi);
 
 	ret = stop ? gsi_channel_stop_retry(channel) : 0;
-
-	if (ret)
-		napi_enable(&channel->napi);
+	/* Finally, ensure NAPI polling has finished. */
+	if (!ret)
+		napi_synchronize(&channel->napi);
 
 	return ret;
 }
@@ -947,10 +951,13 @@ int gsi_channel_stop(struct gsi *gsi, u32 channel_id)
 
 	/* Only disable the completion interrupt if stop is successful */
 	ret = __gsi_channel_stop(channel, true);
-	if (!ret)
-		gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
+	if (ret)
+		return ret;
 
-	return ret;
+	gsi_irq_ieob_disable_one(gsi, channel->evt_ring_id);
+	napi_disable(&channel->napi);
+
+	return 0;
 }
 
 /* Reset and reconfigure a channel, (possibly) enabling the doorbell engine */
-- 
2.27.0