linux-kernel - [PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances

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Date: Tue, 18 Jun 2024 21:13:05 +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>,
        <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>,
        <dmitry.baryshkov@...aro.org>, <abel.vesa@...aro.org>
Subject: [PATCH V2 2/3] 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. Handle the ensuing race introduced 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>
---

v2:
* Use explicit request/free irq and add comments regarding the race
  introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]

 drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
index fb323b3364db..4a4e28b41509 100644
--- a/drivers/soc/qcom/icc-bwmon.c
+++ b/drivers/soc/qcom/icc-bwmon.c
@@ -781,9 +781,10 @@ 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 */
+	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");
 
@@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
 	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
 
 	bwmon_disable(bwmon);
+
+	/*
+	 * Handle the race introduced, when dealing with multiple bwmon instances
+	 * using a shared interrupt line, by relying on bwmon_disable to disable
+	 * the interrupt and followed by an explicit free.
+	 */
+	free_irq(bwmon->irq, bwmon);
 }
 
 static const struct icc_bwmon_data msm8998_bwmon_data = {
-- 
2.34.1