linux-kernel - [PATCH v2 2/2] iommu/riscv: create a auxiliary device for HPM

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Message-ID: <20260208063848.3547817-3-zong.li@sifive.com>
Date: Sat,  7 Feb 2026 22:38:36 -0800
From: Zong Li <zong.li@...ive.com>
To: tjeznach@...osinc.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	robh@...nel.org,
	pjw@...nel.org,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	mark.rutland@....com,
	conor+dt@...nel.org,
	krzk@...nel.org,
	guoyaxing@...c.ac.cn,
	luxu.kernel@...edance.com,
	lv.zheng@...ux.spacemit.com,
	andrew.jones@....qualcomm.com,
	linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev,
	linux-riscv@...ts.infradead.org,
	linux-perf-users@...r.kernel.org
Cc: Zong Li <zong.li@...ive.com>,
	Samuel Holland <samuel.holland@...ive.com>
Subject: [PATCH v2 2/2] iommu/riscv: create a auxiliary device for HPM

Create an auxiliary device for HPM when the IOMMU supports a
hardware performance monitor.

Suggested-by: Samuel Holland <samuel.holland@...ive.com>
Signed-off-by: Zong Li <zong.li@...ive.com>
---
 drivers/iommu/riscv/iommu.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index d9429097a2b5..7cdb80d4343d 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -14,6 +14,7 @@
 
 #include <linux/acpi.h>
 #include <linux/acpi_rimt.h>
+#include <linux/auxiliary_bus.h>
 #include <linux/compiler.h>
 #include <linux/crash_dump.h>
 #include <linux/init.h>
@@ -559,6 +560,22 @@ static irqreturn_t riscv_iommu_fltq_process(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+/*
+ * IOMMU Hardware performance monitor
+ */
+static int riscv_iommu_hpm_enable(struct riscv_iommu_device *iommu)
+{
+	struct auxiliary_device *auxdev;
+
+	/* TODO: for custom event support, the modname should come from compatible */
+	auxdev = __devm_auxiliary_device_create(iommu->dev, KBUILD_MODNAME,
+						"pmu", iommu, 0);
+	if (!auxdev)
+		return -ENODEV;
+
+	return 0;
+}
+
 /* Lookup and initialize device context info structure. */
 static struct riscv_iommu_dc *riscv_iommu_get_dc(struct riscv_iommu_device *iommu,
 						 unsigned int devid)
@@ -1669,6 +1686,9 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu)
 		goto err_remove_sysfs;
 	}
 
+	if (iommu->caps & RISCV_IOMMU_CAPABILITIES_HPM)
+		riscv_iommu_hpm_enable(iommu);
+
 	return 0;
 
 err_remove_sysfs:
-- 
2.43.7