linux-kernel - [PATCH V3 3/4] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances

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Date: Mon, 24 Jun 2024 14:52:13 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: <andersson@...nel.org>, <konrad.dybcio@...aro.org>, <djakov@...nel.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <dmitry.baryshkov@...aro.org>, <srinivas.kandagatla@...aro.org>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <quic_rgottimu@...cinc.com>, <quic_kshivnan@...cinc.com>,
        <quic_sibis@...cinc.com>, <conor+dt@...nel.org>,
        <abel.vesa@...aro.org>
Subject: [PATCH V3 3/4] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances

The multiple BWMONv4 instances available on the X1E80100 SoC use the
same interrupt number. Mark them are shared to allow for re-use across
instances.

Using IRQF_SHARED coupled with devm_request_threaded_irq implies that
the irq can still trigger during/after bwmon_remove due to other active
bwmon instances. Handle this race by relying on bwmon_disable to disable
the interrupt and coupled with explicit request/free irqs.

Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
---

v3:
* Update commit message describing the race condition. [Bjorn]
* Update comment in the bwmon driver. [Dmitry]

 drivers/soc/qcom/icc-bwmon.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
index ecddb60bd665..e7851974084b 100644
--- a/drivers/soc/qcom/icc-bwmon.c
+++ b/drivers/soc/qcom/icc-bwmon.c
@@ -783,9 +783,14 @@ static int bwmon_probe(struct platform_device *pdev)
 	bwmon->dev = dev;
 
 	bwmon_disable(bwmon);
-	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
-					bwmon_intr_thread,
-					IRQF_ONESHOT, dev_name(dev), bwmon);
+
+	/*
+	 * SoCs with multiple cpu-bwmon instances can end up using a shared interrupt
+	 * line. Using the devm_ variant might result in the IRQ handler being executed
+	 * after bwmon_disable in bwmon_remove()
+	 */
+	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
+				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
 	if (ret)
 		return dev_err_probe(dev, ret, "failed to request IRQ\n");
 
@@ -800,6 +805,7 @@ static void bwmon_remove(struct platform_device *pdev)
 	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
 
 	bwmon_disable(bwmon);
+	free_irq(bwmon->irq, bwmon);
 }
 
 static const struct icc_bwmon_data msm8998_bwmon_data = {
-- 
2.34.1