perf: arm_cspmu: Separate Arm and vendor module

Arm Coresight PMU driver consists of main standard code and
vendor backend code. Both are currently built as a single module.
This patch adds vendor registration API to separate the two to
keep things modular. The main driver requests each known backend
module during initialization and defer device binding process.
The backend module then registers an init callback to the main
driver and continue the device driver binding process.

Signed-off-by: Besar Wicaksono <bwicaksono@nvidia.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-and-tested-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Link: https://lore.kernel.org/r/20230821231608.50911-1-bwicaksono@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 133 insertions, 35 deletions

diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
index e2b7827c4563..c59f1e5a35a3 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.c
+++ b/drivers/perf/arm_cspmu/arm_cspmu.c
@@ -16,7 +16,7 @@
  * The user should refer to the vendor technical documentation to get details
  * about the supported events.
  *
- * Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * Copyright (c) 2022-2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  *
  */
 
@@ -26,11 +26,11 @@
 #include <linux/interrupt.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/perf_event.h>
 #include <linux/platform_device.h>
 
 #include "arm_cspmu.h"
-#include "nvidia_cspmu.h"
 
 #define PMUNAME "arm_cspmu"
 #define DRVNAME "arm-cs-arch-pmu"
@@ -112,11 +112,10 @@
  */
 #define HILOHI_MAX_POLL	1000
 
-/* JEDEC-assigned JEP106 identification code */
-#define ARM_CSPMU_IMPL_ID_NVIDIA		0x36B
-
 static unsigned long arm_cspmu_cpuhp_state;
 
+static DEFINE_MUTEX(arm_cspmu_lock);
+
 static struct acpi_apmt_node *arm_cspmu_apmt_node(struct device *dev)
 {
 	return *(struct acpi_apmt_node **)dev_get_platdata(dev);
@@ -373,27 +372,37 @@ static struct attribute_group arm_cspmu_cpumask_attr_group = {
 	.attrs = arm_cspmu_cpumask_attrs,
 };
 
-struct impl_match {
-	u32 pmiidr;
-	u32 mask;
-	int (*impl_init_ops)(struct arm_cspmu *cspmu);
-};
-
-static const struct impl_match impl_match[] = {
+static struct arm_cspmu_impl_match impl_match[] = {
 	{
-	  .pmiidr = ARM_CSPMU_IMPL_ID_NVIDIA,
-	  .mask = ARM_CSPMU_PMIIDR_IMPLEMENTER,
-	  .impl_init_ops = nv_cspmu_init_ops
+		.module_name	= "nvidia_cspmu",
+		.pmiidr_val	= ARM_CSPMU_IMPL_ID_NVIDIA,
+		.pmiidr_mask	= ARM_CSPMU_PMIIDR_IMPLEMENTER,
+		.module		= NULL,
+		.impl_init_ops	= NULL,
 	},
-	{}
+	{0}
 };
 
+static struct arm_cspmu_impl_match *arm_cspmu_impl_match_get(u32 pmiidr)
+{
+	struct arm_cspmu_impl_match *match = impl_match;
+
+	for (; match->pmiidr_val; match++) {
+		u32 mask = match->pmiidr_mask;
+
+		if ((match->pmiidr_val & mask) == (pmiidr & mask))
+			return match;
+	}
+
+	return NULL;
+}
+
 static int arm_cspmu_init_impl_ops(struct arm_cspmu *cspmu)
 {
-	int ret;
+	int ret = 0;
 	struct arm_cspmu_impl_ops *impl_ops = &cspmu->impl.ops;
 	struct acpi_apmt_node *apmt_node = arm_cspmu_apmt_node(cspmu->dev);
-	const struct impl_match *match = impl_match;
+	struct arm_cspmu_impl_match *match;
 
 	/*
 	 * Get PMU implementer and product id from APMT node.
@@ -405,17 +414,36 @@ static int arm_cspmu_init_impl_ops(struct arm_cspmu *cspmu)
 				       readl(cspmu->base0 + PMIIDR);
 
 	/* Find implementer specific attribute ops. */
-	for (; match->pmiidr; match++) {
-		const u32 mask = match->mask;
+	match = arm_cspmu_impl_match_get(cspmu->impl.pmiidr);
+
+	/* Load implementer module and initialize the callbacks. */
+	if (match) {
+		mutex_lock(&arm_cspmu_lock);
+
+		if (match->impl_init_ops) {
+			/* Prevent unload until PMU registration is done. */
+			if (try_module_get(match->module)) {
+				cspmu->impl.module = match->module;
+				cspmu->impl.match = match;
+				ret = match->impl_init_ops(cspmu);
+				if (ret)
+					module_put(match->module);
+			} else {
+				WARN(1, "arm_cspmu failed to get module: %s\n",
+					match->module_name);
+				ret = -EINVAL;
+			}
+		} else {
+			request_module_nowait(match->module_name);
+			ret = -EPROBE_DEFER;
+		}
 
-		if ((match->pmiidr & mask) == (cspmu->impl.pmiidr & mask)) {
-			ret = match->impl_init_ops(cspmu);
-			if (ret)
-				return ret;
+		mutex_unlock(&arm_cspmu_lock);
 
-			break;
-		}
-	}
+		if (ret)
+			return ret;
+	} else
+		cspmu->impl.module = THIS_MODULE;
 
 	/* Use default callbacks if implementer doesn't provide one. */
 	CHECK_DEFAULT_IMPL_OPS(impl_ops, get_event_attrs);
@@ -478,11 +506,6 @@ arm_cspmu_alloc_attr_group(struct arm_cspmu *cspmu)
 	struct attribute_group **attr_groups = NULL;
 	struct device *dev = cspmu->dev;
 	const struct arm_cspmu_impl_ops *impl_ops = &cspmu->impl.ops;
-	int ret;
-
-	ret = arm_cspmu_init_impl_ops(cspmu);
-	if (ret)
-		return NULL;
 
 	cspmu->identifier = impl_ops->get_identifier(cspmu);
 	cspmu->name = impl_ops->get_name(cspmu);
@@ -1149,7 +1172,7 @@ static int arm_cspmu_register_pmu(struct arm_cspmu *cspmu)
 
 	cspmu->pmu = (struct pmu){
 		.task_ctx_nr	= perf_invalid_context,
-		.module		= THIS_MODULE,
+		.module		= cspmu->impl.module,
 		.pmu_enable	= arm_cspmu_enable,
 		.pmu_disable	= arm_cspmu_disable,
 		.event_init	= arm_cspmu_event_init,
@@ -1196,11 +1219,17 @@ static int arm_cspmu_device_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	ret = arm_cspmu_register_pmu(cspmu);
+	ret = arm_cspmu_init_impl_ops(cspmu);
 	if (ret)
 		return ret;
 
-	return 0;
+	ret = arm_cspmu_register_pmu(cspmu);
+
+	/* Matches arm_cspmu_init_impl_ops() above. */
+	if (cspmu->impl.module != THIS_MODULE)
+		module_put(cspmu->impl.module);
+
+	return ret;
 }
 
 static int arm_cspmu_device_remove(struct platform_device *pdev)
@@ -1300,6 +1329,75 @@ static void __exit arm_cspmu_exit(void)
 	cpuhp_remove_multi_state(arm_cspmu_cpuhp_state);
 }
 
+int arm_cspmu_impl_register(const struct arm_cspmu_impl_match *impl_match)
+{
+	struct arm_cspmu_impl_match *match;
+	int ret = 0;
+
+	match = arm_cspmu_impl_match_get(impl_match->pmiidr_val);
+
+	if (match) {
+		mutex_lock(&arm_cspmu_lock);
+
+		if (!match->impl_init_ops) {
+			match->module = impl_match->module;
+			match->impl_init_ops = impl_match->impl_init_ops;
+		} else {
+			/* Broken match table may contain non-unique entries */
+			WARN(1, "arm_cspmu backend already registered for module: %s, pmiidr: 0x%x, mask: 0x%x\n",
+				match->module_name,
+				match->pmiidr_val,
+				match->pmiidr_mask);
+
+			ret = -EINVAL;
+		}
+
+		mutex_unlock(&arm_cspmu_lock);
+
+		if (!ret)
+			ret = driver_attach(&arm_cspmu_driver.driver);
+	} else {
+		pr_err("arm_cspmu reg failed, unable to find a match for pmiidr: 0x%x\n",
+			impl_match->pmiidr_val);
+
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(arm_cspmu_impl_register);
+
+static int arm_cspmu_match_device(struct device *dev, const void *match)
+{
+	struct arm_cspmu *cspmu = platform_get_drvdata(to_platform_device(dev));
+
+	return (cspmu && cspmu->impl.match == match) ? 1 : 0;
+}
+
+void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match *impl_match)
+{
+	struct device *dev;
+	struct arm_cspmu_impl_match *match;
+
+	match = arm_cspmu_impl_match_get(impl_match->pmiidr_val);
+
+	if (WARN_ON(!match))
+		return;
+
+	/* Unbind the driver from all matching backend devices. */
+	while ((dev = driver_find_device(&arm_cspmu_driver.driver, NULL,
+			match, arm_cspmu_match_device)))
+		device_release_driver(dev);
+
+	mutex_lock(&arm_cspmu_lock);
+
+	match->module = NULL;
+	match->impl_init_ops = NULL;
+
+	mutex_unlock(&arm_cspmu_lock);
+}
+EXPORT_SYMBOL_GPL(arm_cspmu_impl_unregister);
+
 module_init(arm_cspmu_init);
 module_exit(arm_cspmu_exit);