linux-kernel - [PATCH net 1/2] net: ipa: directly disable ipa-setup-ready interrupt

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Message-Id: <20211123001555.505546-2-elder@linaro.org>
Date:   Mon, 22 Nov 2021 18:15:54 -0600
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     pkurapat@...eaurora.org, avuyyuru@...eaurora.org,
        bjorn.andersson@...aro.org, cpratapa@...eaurora.org,
        subashab@...eaurora.org, evgreen@...omium.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net 1/2] net: ipa: directly disable ipa-setup-ready interrupt

We currently maintain a "disabled" Boolean flag to determine whether
the "ipa-setup-ready" SMP2P IRQ handler does anything.  That flag
must be accessed under protection of a mutex.

Instead, disable the SMP2P interrupt when requested, which prevents
the interrupt handler from ever being called.  More importantly, it
synchronizes a thread disabling the interrupt with the completion of
the interrupt handler in case they run concurrently.

Use the IPA setup_complete flag rather than the disabled flag in the
handler to determine whether to ignore any interrupts arriving after
the first.

Rename the "disabled" flag to be "setup_disabled", to be specific
about its purpose.

Fixes: 530f9216a953 ("soc: qcom: ipa: AP/modem communications")
Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_smp2p.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ipa/ipa_smp2p.c b/drivers/net/ipa/ipa_smp2p.c
index df7639c39d716..24bc112a072c6 100644
--- a/drivers/net/ipa/ipa_smp2p.c
+++ b/drivers/net/ipa/ipa_smp2p.c
@@ -53,7 +53,7 @@
  * @setup_ready_irq:	IPA interrupt triggered by modem to signal GSI ready
  * @power_on:		Whether IPA power is on
  * @notified:		Whether modem has been notified of power state
- * @disabled:		Whether setup ready interrupt handling is disabled
+ * @setup_disabled:	Whether setup ready interrupt handler is disabled
  * @mutex:		Mutex protecting ready-interrupt/shutdown interlock
  * @panic_notifier:	Panic notifier structure
 */
@@ -67,7 +67,7 @@ struct ipa_smp2p {
 	u32 setup_ready_irq;
 	bool power_on;
 	bool notified;
-	bool disabled;
+	bool setup_disabled;
 	struct mutex mutex;
 	struct notifier_block panic_notifier;
 };
@@ -155,11 +155,9 @@ static irqreturn_t ipa_smp2p_modem_setup_ready_isr(int irq, void *dev_id)
 	struct device *dev;
 	int ret;
 
-	mutex_lock(&smp2p->mutex);
-
-	if (smp2p->disabled)
-		goto out_mutex_unlock;
-	smp2p->disabled = true;		/* If any others arrive, ignore them */
+	/* Ignore any (spurious) interrupts received after the first */
+	if (smp2p->ipa->setup_complete)
+		return IRQ_HANDLED;
 
 	/* Power needs to be active for setup */
 	dev = &smp2p->ipa->pdev->dev;
@@ -176,8 +174,6 @@ static irqreturn_t ipa_smp2p_modem_setup_ready_isr(int irq, void *dev_id)
 out_power_put:
 	pm_runtime_mark_last_busy(dev);
 	(void)pm_runtime_put_autosuspend(dev);
-out_mutex_unlock:
-	mutex_unlock(&smp2p->mutex);
 
 	return IRQ_HANDLED;
 }
@@ -322,7 +318,10 @@ void ipa_smp2p_disable(struct ipa *ipa)
 
 	mutex_lock(&smp2p->mutex);
 
-	smp2p->disabled = true;
+	if (!smp2p->setup_disabled) {
+		disable_irq(smp2p->setup_ready_irq);
+		smp2p->setup_disabled = true;
+	}
 
 	mutex_unlock(&smp2p->mutex);
 }
-- 
2.32.0