1 files changed, 138 insertions, 0 deletions
diff --git a/drivers/cpufreq/sc520_freq.c b/drivers/cpufreq/sc520_freq.c
new file mode 100644
index 0000000000..330c8d6cf9
--- /dev/null
+++ b/drivers/cpufreq/sc520_freq.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	sc520_freq.c: cpufreq driver for the AMD Elan sc520
+ *
+ *	Copyright (C) 2005 Sean Young <sean@mess.org>
+ *
+ *	Based on elanfreq.c
+ *
+ *	2005-03-30: - initial revision
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+#include <linux/delay.h>
+#include <linux/cpufreq.h>
+#include <linux/timex.h>
+#include <linux/io.h>
+
+#include <asm/cpu_device_id.h>
+#include <asm/msr.h>
+
+#define MMCR_BASE	0xfffef000	/* The default base address */
+#define OFFS_CPUCTL	0x2   /* CPU Control Register */
+
+static __u8 __iomem *cpuctl;
+
+static struct cpufreq_frequency_table sc520_freq_table[] = {
+	{0, 0x01,	100000},
+	{0, 0x02,	133000},
+	{0, 0,	CPUFREQ_TABLE_END},
+};
+
+static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
+{
+	u8 clockspeed_reg = *cpuctl;
+
+	switch (clockspeed_reg & 0x03) {
+	default:
+		pr_err("error: cpuctl register has unexpected value %02x\n",
+		       clockspeed_reg);
+		fallthrough;
+	case 0x01:
+		return 100000;
+	case 0x02:
+		return 133000;
+	}
+}
+
+static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
+{
+
+	u8 clockspeed_reg;
+
+	local_irq_disable();
+
+	clockspeed_reg = *cpuctl & ~0x03;
+	*cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
+
+	local_irq_enable();
+
+	return 0;
+}
+
+/*
+ *	Module init and exit code
+ */
+
+static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
+{
+	struct cpuinfo_x86 *c = &cpu_data(0);
+
+	/* capability check */
+	if (c->x86_vendor != X86_VENDOR_AMD ||
+	    c->x86 != 4 || c->x86_model != 9)
+		return -ENODEV;
+
+	/* cpuinfo and default policy values */
+	policy->cpuinfo.transition_latency = 1000000; /* 1ms */
+	policy->freq_table = sc520_freq_table;
+
+	return 0;
+}
+
+
+static struct cpufreq_driver sc520_freq_driver = {
+	.get	= sc520_freq_get_cpu_frequency,
+	.verify	= cpufreq_generic_frequency_table_verify,
+	.target_index = sc520_freq_target,
+	.init	= sc520_freq_cpu_init,
+	.name	= "sc520_freq",
+	.attr	= cpufreq_generic_attr,
+};
+
+static const struct x86_cpu_id sc520_ids[] = {
+	X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 9, NULL),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
+
+static int __init sc520_freq_init(void)
+{
+	int err;
+
+	if (!x86_match_cpu(sc520_ids))
+		return -ENODEV;
+
+	cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
+	if (!cpuctl) {
+		pr_err("sc520_freq: error: failed to remap memory\n");
+		return -ENOMEM;
+	}
+
+	err = cpufreq_register_driver(&sc520_freq_driver);
+	if (err)
+		iounmap(cpuctl);
+
+	return err;
+}
+
+
+static void __exit sc520_freq_exit(void)
+{
+	cpufreq_unregister_driver(&sc520_freq_driver);
+	iounmap(cpuctl);
+}
+
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sean Young <sean@mess.org>");
+MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
+
+module_init(sc520_freq_init);
+module_exit(sc520_freq_exit);
+