nvidia-oot: cpuidle: Add idle debugfs nodes

Adding debugfs support to force cpus into idle states. Building as
module instead of driver. Generic to support any standard cpuidle
implementation.

Bug 3583597

Change-Id: I5dd9e8635b844f465bc4c9da7e1d45ee17dd669f
Signed-off-by: Ishan Shah <ishah@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/2814926
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

dkms.conf

@@ -115,4 +115,8 @@ BUILT_MODULE_NAME[27]="generic-pwm-tachometer"
 BUILT_MODULE_LOCATION[27]="drivers/hwmon"
 DEST_MODULE_LOCATION[27]="/extra"
 
+BUILT_MODULE_NAME[28]="cpuidle-debugfs"
+BUILT_MODULE_LOCATION[28]="drivers/cpuidle"
+DEST_MODULE_LOCATION[28]="/extra"
+
 AUTO_INSTALL="yes"

drivers/Makefile

@@ -7,6 +7,7 @@ obj-m += block/tegra_virt_storage/
 obj-m += block/tegra_oops_virt_storage/
 obj-m += c2c/
 obj-m += clink/
+obj-m += cpuidle/
 obj-m += crypto/
 obj-m += debug/
 obj-m += devfreq/

drivers/cpuidle/Makefile

@@ -1,2 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
 
 obj-m += cpuidle-tegra-auto.o
+obj-m += cpuidle-debugfs.o

drivers/cpuidle/cpuidle-debugfs.c

@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All Rights Reserved.
+ *
+ * Module to force cpuidle states through debugfs files.
+ *
+ */
+#include <linux/module.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+#include <linux/interrupt.h>
+#include <linux/debugfs.h>
+#include <linux/cpu.h>
+#include <linux/cpuidle.h>
+
+#define US_TO_NS(x) (1000 * x)
+
+static struct cpuidle_driver *drv;
+
+static bool is_timer_irq(struct irq_desc *desc)
+{
+	return desc && desc->action && (desc->action->flags & IRQF_TIMER);
+}
+
+static void suspend_all_device_irqs(void)
+{
+	struct irq_data *data;
+	struct irq_desc *desc;
+	int irq;
+
+	for (irq = 0, data = irq_get_irq_data(irq); irq < nr_irqs;
+			irq++, data = irq_get_irq_data(irq)) {
+		if (!data)
+			continue;
+		desc = irq_data_to_desc(data);
+		if (!desc || is_timer_irq(desc))
+			continue;
+		irq_set_status_flags(irq, IRQ_DISABLE_UNLAZY);
+		disable_irq_nosync(irq);
+	}
+}
+
+static void resume_all_device_irqs(void)
+{
+	struct irq_data *data;
+	struct irq_desc *desc;
+	int irq;
+
+	for (irq = 0, data = irq_get_irq_data(irq); irq < nr_irqs;
+			irq++, data = irq_get_irq_data(irq)) {
+		if (!data)
+			continue;
+		desc = irq_data_to_desc(data);
+		if (!desc || is_timer_irq(desc))
+			continue;
+		enable_irq(desc->irq_data.irq);
+		irq_clear_status_flags(irq, IRQ_DISABLE_UNLAZY);
+	}
+}
+
+static int forced_idle_write(void *data, u64 val)
+{
+	struct cpuidle_state *idle_state = (struct cpuidle_state *) data;
+	int ret = 0;
+	u64 duration_ns = US_TO_NS(val);
+
+	suspend_all_device_irqs();
+	/* duration_ns, latency_ns */
+	play_idle_precise(duration_ns, (u64) (idle_state->exit_latency_ns));
+	resume_all_device_irqs();
+
+	return ret;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(idle_state_fops, NULL, forced_idle_write, "%llu\n");
+
+static struct dentry *cpuidle_debugfs_node;
+
+static int init_debugfs(void)
+{
+	int i;
+
+	cpuidle_debugfs_node = debugfs_create_dir("cpuidle_debug", NULL);
+	if (!cpuidle_debugfs_node)
+		goto err_out;
+
+	for (i = 0; i < drv->state_count; i++) {
+		debugfs_create_file(drv->states[i].name, 0200,
+			cpuidle_debugfs_node, &(drv->states[i]), &idle_state_fops);
+	}
+	return 0;
+
+err_out:
+	pr_err("%s: Couldn't create debugfs node for cpuidle\n", __func__);
+	debugfs_remove_recursive(cpuidle_debugfs_node);
+	return -ENOMEM;
+}
+
+static int __init cpuidle_debugfs_probe(void)
+{
+	drv = cpuidle_get_driver();
+	init_debugfs();
+	return 0;
+}
+
+static void __exit cpuidle_debugfs_remove(void)
+{
+	debugfs_remove_recursive(cpuidle_debugfs_node);
+}
+
+module_init(cpuidle_debugfs_probe);
+module_exit(cpuidle_debugfs_remove);
+
+MODULE_AUTHOR("Ishan Shah <ishah@nvidia.com>");
+MODULE_DESCRIPTION("cpuidle debugfs driver");
+MODULE_LICENSE("GPL");