linux-kernel - [PATCH net-next 2/2] net: ipa: do not clear interrupt in gsi_channel

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Message-Id: <20200515200731.2931-3-elder@linaro.org>
Date:   Fri, 15 May 2020 15:07:31 -0500
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net
Cc:     evgreen@...omium.org.net, subashab@...eaurora.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 2/2] net: ipa: do not clear interrupt in gsi_channel_start()

In gsi_channel_start() there is harmless-looking comment "Clear the
channel's event ring interrupt in case it's pending".  The intent
was to avoid getting spurious interrupts when first bringing up a
channel.

However we now use channel stop/start to implement suspend and
resume, and an interrupt pending at the time we resume is actually
something we don't want to ignore.

The very first time we bring up the channel we do not expect an
interrupt to be pending, and even if it were, the effect would
simply be to schedule NAPI on that channel, which would find nothing
to do, which is not a problem.

Stop clearing any pending IEOB interrupt in gsi_channel_start().
That leaves one caller of the trivial function gsi_isr_ieob_clear().
Get rid of that function and just open-code it in gsi_isr_ieob()
instead.

This fixes a problem where suspend/resume IPA v4.2 would get stuck
when resuming after a suspend.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/gsi.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 66570609c845..d343dc94cb48 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -238,11 +238,6 @@ static void gsi_irq_ieob_enable(struct gsi *gsi, u32 evt_ring_id)
 	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
 }

-static void gsi_isr_ieob_clear(struct gsi *gsi, u32 mask)
-{
-	iowrite32(mask, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_CLR_OFFSET);
-}
-
 static void gsi_irq_ieob_disable(struct gsi *gsi, u32 evt_ring_id)
 {
 	u32 val;
@@ -777,7 +772,6 @@ static void gsi_channel_deprogram(struct gsi_channel *channel)
 int gsi_channel_start(struct gsi *gsi, u32 channel_id)
 {
 	struct gsi_channel *channel = &gsi->channel[channel_id];
-	u32 evt_ring_id = channel->evt_ring_id;
 	int ret;

 	mutex_lock(&gsi->mutex);
@@ -786,9 +780,6 @@ int gsi_channel_start(struct gsi *gsi, u32 channel_id)

 	mutex_unlock(&gsi->mutex);

-	/* Clear the channel's event ring interrupt in case it's pending */
-	gsi_isr_ieob_clear(gsi, BIT(evt_ring_id));
-
 	gsi_channel_thaw(channel);

 	return ret;
@@ -1093,7 +1084,7 @@ static void gsi_isr_ieob(struct gsi *gsi)
 	u32 event_mask;

 	event_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_OFFSET);
-	gsi_isr_ieob_clear(gsi, event_mask);
+	iowrite32(event_mask, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_CLR_OFFSET);

 	while (event_mask) {
 		u32 evt_ring_id = __ffs(event_mask);
-- 
2.20.1