[PATCH 2/2] Add cpufreq driver for Momentum Maple boards

[Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>]

Add simple cpufreq driver for Maple-based boards (ppc970fx evaluation
kit and others). Driver is based on a cpufreq driver for 64-bit powermac
boxes with all pmac-dependant features removed and simple cleanup
applied.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
---
 drivers/cpufreq/Kconfig         |    5 +
 drivers/cpufreq/Kconfig.powerpc |    7 +
 drivers/cpufreq/Makefile        |    5 +
 drivers/cpufreq/maple-cpufreq.c |  314 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 331 insertions(+), 0 deletions(-)
 create mode 100644 drivers/cpufreq/Kconfig.powerpc
 create mode 100644 drivers/cpufreq/maple-cpufreq.c

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 9fb8485..61ae639 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -184,5 +184,10 @@ depends on X86
 source "drivers/cpufreq/Kconfig.x86"
 endmenu
 
+menu "PowerPC CPU frequency scaling drivers"
+depends on PPC32 || PPC64
+source "drivers/cpufreq/Kconfig.powerpc"
+endmenu
+
 endif
 endmenu
diff --git a/drivers/cpufreq/Kconfig.powerpc b/drivers/cpufreq/Kconfig.powerpc
new file mode 100644
index 0000000..e76992f
--- /dev/null
+++ b/drivers/cpufreq/Kconfig.powerpc
@@ -0,0 +1,7 @@
+config CPU_FREQ_MAPLE
+	bool "Support for Maple 970FX Evaluation Board"
+	depends on PPC_MAPLE
+	select CPU_FREQ_TABLE
+	help
+	  This adds support for frequency switching on Maple 970FX
+	  Evaluation Board and compatible boards (IBM JS2x blades).
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index e2fc2d2..ca3796d 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -41,3 +41,8 @@ obj-$(CONFIG_X86_CPUFREQ_NFORCE2)	+= cpufreq-nforce2.o
 
 # ARM SoC drivers
 obj-$(CONFIG_UX500_SOC_DB8500)		+= db8500-cpufreq.o
+
+
+##################################################################################d
+# PowerPC platform drivers
+obj-$(CONFIG_CPU_FREQ_MAPLE)		+= maple-cpufreq.o
diff --git a/drivers/cpufreq/maple-cpufreq.c b/drivers/cpufreq/maple-cpufreq.c
new file mode 100644
index 0000000..a61f6b9
--- /dev/null
+++ b/drivers/cpufreq/maple-cpufreq.c
@@ -0,0 +1,314 @@
+/*
+ *  Copyright (C) 2011 Dmitry Eremin-Solenikov
+ *  Copyright (C) 2002 - 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ *  and                       Markus Demleitner <msdemlei@cl.uni-heidelberg.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This driver adds basic cpufreq support for SMU & 970FX based G5 Macs,
+ * that is iMac G5 and latest single CPU desktop.
+ */
+
+#undef DEBUG
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/cpufreq.h>
+#include <linux/init.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/time.h>
+#include <linux/of.h>
+
+#define DBG(fmt...) pr_debug(fmt)
+
+/* see 970FX user manual */
+
+#define SCOM_PCR 0x0aa001			/* PCR scom addr */
+
+#define PCR_HILO_SELECT		0x80000000U	/* 1 = PCR, 0 = PCRH */
+#define PCR_SPEED_FULL		0x00000000U	/* 1:1 speed value */
+#define PCR_SPEED_HALF		0x00020000U	/* 1:2 speed value */
+#define PCR_SPEED_QUARTER	0x00040000U	/* 1:4 speed value */
+#define PCR_SPEED_MASK		0x000e0000U	/* speed mask */
+#define PCR_SPEED_SHIFT		17
+#define PCR_FREQ_REQ_VALID	0x00010000U	/* freq request valid */
+#define PCR_VOLT_REQ_VALID	0x00008000U	/* volt request valid */
+#define PCR_TARGET_TIME_MASK	0x00006000U	/* target time */
+#define PCR_STATLAT_MASK	0x00001f00U	/* STATLAT value */
+#define PCR_SNOOPLAT_MASK	0x000000f0U	/* SNOOPLAT value */
+#define PCR_SNOOPACC_MASK	0x0000000fU	/* SNOOPACC value */
+
+#define SCOM_PSR 0x408001			/* PSR scom addr */
+/* warning: PSR is a 64 bits register */
+#define PSR_CMD_RECEIVED	0x2000000000000000U   /* command received */
+#define PSR_CMD_COMPLETED	0x1000000000000000U   /* command completed */
+#define PSR_CUR_SPEED_MASK	0x0300000000000000U   /* current speed */
+#define PSR_CUR_SPEED_SHIFT	(56)
+
+/*
+ * The G5 only supports two frequencies (Quarter speed is not supported)
+ */
+#define CPUFREQ_HIGH                  0
+#define CPUFREQ_LOW                   1
+
+static struct cpufreq_frequency_table maple_cpu_freqs[] = {
+	{CPUFREQ_HIGH,		0},
+	{CPUFREQ_LOW,		0},
+	{0,			CPUFREQ_TABLE_END},
+};
+
+static struct freq_attr *maple_cpu_freqs_attr[] = {
+	&cpufreq_freq_attr_scaling_available_freqs,
+	NULL,
+};
+
+/* Power mode data is an array of the 32 bits PCR values to use for
+ * the various frequencies, retrieved from the device-tree
+ */
+static int maple_pmode_cur;
+
+static DEFINE_MUTEX(maple_switch_mutex);
+
+static const u32 *maple_pmode_data;
+static int maple_pmode_max;
+
+/*
+ * Fake voltage switching for platforms with missing support
+ */
+
+static void maple_dummy_switch_volt(int speed_mode)
+{
+}
+
+/*
+ * SCOM based frequency switching for 970FX rev3
+ */
+static int maple_scom_switch_freq(int speed_mode)
+{
+	unsigned long flags;
+	int to;
+
+	/* If frequency is going up, first ramp up the voltage */
+	if (speed_mode < maple_pmode_cur)
+		maple_dummy_switch_volt(speed_mode);
+
+	local_irq_save(flags);
+
+	/* Clear PCR high */
+	scom970_write(SCOM_PCR, 0);
+	/* Clear PCR low */
+	scom970_write(SCOM_PCR, PCR_HILO_SELECT | 0);
+	/* Set PCR low */
+	scom970_write(SCOM_PCR, PCR_HILO_SELECT |
+		      maple_pmode_data[speed_mode]);
+
+	/* Wait for completion */
+	for (to = 0; to < 10; to++) {
+		unsigned long psr = scom970_read(SCOM_PSR);
+
+		if ((psr & PSR_CMD_RECEIVED) == 0 &&
+		    (((psr >> PSR_CUR_SPEED_SHIFT) ^
+		      (maple_pmode_data[speed_mode] >> PCR_SPEED_SHIFT)) & 0x3)
+		    == 0)
+			break;
+		if (psr & PSR_CMD_COMPLETED)
+			break;
+		udelay(100);
+	}
+
+	local_irq_restore(flags);
+
+	/* If frequency is going down, last ramp the voltage */
+	if (speed_mode > maple_pmode_cur)
+		maple_dummy_switch_volt(speed_mode);
+
+	maple_pmode_cur = speed_mode;
+	ppc_proc_freq = maple_cpu_freqs[speed_mode].frequency * 1000ul;
+
+	return 0;
+}
+
+static int maple_scom_query_freq(void)
+{
+	unsigned long psr = scom970_read(SCOM_PSR);
+	int i;
+
+	for (i = 0; i <= maple_pmode_max; i++)
+		if ((((psr >> PSR_CUR_SPEED_SHIFT) ^
+		      (maple_pmode_data[i] >> PCR_SPEED_SHIFT)) & 0x3) == 0)
+			break;
+	return i;
+}
+
+/*
+ * Common interface to the cpufreq core
+ */
+
+static int maple_cpufreq_verify(struct cpufreq_policy *policy)
+{
+	return cpufreq_frequency_table_verify(policy, maple_cpu_freqs);
+}
+
+static int maple_cpufreq_target(struct cpufreq_policy *policy,
+	unsigned int target_freq, unsigned int relation)
+{
+	unsigned int newstate = 0;
+	struct cpufreq_freqs freqs;
+	int rc;
+
+	if (cpufreq_frequency_table_target(policy, maple_cpu_freqs,
+			target_freq, relation, &newstate))
+		return -EINVAL;
+
+	if (maple_pmode_cur == newstate)
+		return 0;
+
+	mutex_lock(&maple_switch_mutex);
+
+	freqs.old = maple_cpu_freqs[maple_pmode_cur].frequency;
+	freqs.new = maple_cpu_freqs[newstate].frequency;
+	freqs.cpu = 0;
+
+	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+	rc = maple_scom_switch_freq(newstate);
+	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+	mutex_unlock(&maple_switch_mutex);
+
+	return rc;
+}
+
+static unsigned int maple_cpufreq_get_speed(unsigned int cpu)
+{
+	return maple_cpu_freqs[maple_pmode_cur].frequency;
+}
+
+static int maple_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	policy->cpuinfo.transition_latency = 12000;
+	policy->cur = maple_cpu_freqs[maple_scom_query_freq()].frequency;
+	/* secondary CPUs are tied to the primary one by the
+	 * cpufreq core if in the secondary policy we tell it that
+	 * it actually must be one policy together with all others. */
+	cpumask_copy(policy->cpus, cpu_online_mask);
+	cpufreq_frequency_table_get_attr(maple_cpu_freqs, policy->cpu);
+
+	return cpufreq_frequency_table_cpuinfo(policy,
+		maple_cpu_freqs);
+}
+
+
+static struct cpufreq_driver maple_cpufreq_driver = {
+	.name		= "maple",
+	.owner		= THIS_MODULE,
+	.flags		= CPUFREQ_CONST_LOOPS,
+	.init		= maple_cpufreq_cpu_init,
+	.verify		= maple_cpufreq_verify,
+	.target		= maple_cpufreq_target,
+	.get		= maple_cpufreq_get_speed,
+	.attr		= maple_cpu_freqs_attr,
+};
+
+static int __init maple_cpufreq_init(void)
+{
+	struct device_node *cpus;
+	struct device_node *cpunode;
+	unsigned int psize;
+	unsigned long max_freq;
+	const u32 *valp;
+	u32 pvr_hi;
+	int rc = -ENODEV;
+
+	cpus = of_find_node_by_path("/cpus");
+	if (cpus == NULL) {
+		DBG("No /cpus node !\n");
+		return -ENODEV;
+	}
+
+	/* Get first CPU node */
+	for (cpunode = NULL;
+	     (cpunode = of_get_next_child(cpus, cpunode)) != NULL;) {
+		const u32 *reg = of_get_property(cpunode, "reg", NULL);
+		if (reg == NULL || (*reg) != 0)
+			continue;
+		if (!strcmp(cpunode->type, "cpu"))
+			break;
+	}
+	if (cpunode == NULL) {
+		printk(KERN_ERR "cpufreq: Can't find any CPU 0 node\n");
+		goto bail_cpus;
+	}
+
+	/* Check 970FX for now */
+	/* we actually don't care on which CPU to access PVR */
+	pvr_hi = PVR_VER(mfspr(SPRN_PVR));
+	if (pvr_hi != 0x3c && pvr_hi != 0x44) {
+		printk(KERN_ERR "cpufreq: Unsupported CPU version (%x)\n",
+				pvr_hi);
+		goto bail_noprops;
+	}
+
+	/* Look for the powertune data in the device-tree */
+	maple_pmode_data = of_get_property(cpunode, "power-mode-data", &psize);
+	if (!maple_pmode_data) {
+		DBG("No power-mode-data !\n");
+		goto bail_noprops;
+	}
+	maple_pmode_max = psize / sizeof(u32) - 1;
+
+	/*
+	 * From what I see, clock-frequency is always the maximal frequency.
+	 * The current driver can not slew sysclk yet, so we really only deal
+	 * with powertune steps for now. We also only implement full freq and
+	 * half freq in this version. So far, I haven't yet seen a machine
+	 * supporting anything else.
+	 */
+	valp = of_get_property(cpunode, "clock-frequency", NULL);
+	if (!valp)
+		return -ENODEV;
+	max_freq = (*valp)/1000;
+	maple_cpu_freqs[0].frequency = max_freq;
+	maple_cpu_freqs[1].frequency = max_freq/2;
+
+	/* Force apply current frequency to make sure everything is in
+	 * sync (voltage is right for example). Firmware may leave us with
+	 * a strange setting ...
+	 */
+	maple_dummy_switch_volt(CPUFREQ_HIGH);
+	msleep(10);
+	maple_pmode_cur = -1;
+	maple_scom_switch_freq(maple_scom_query_freq());
+
+	printk(KERN_INFO "Registering G5 CPU frequency driver\n");
+	printk(KERN_INFO "Frequency method: SCOM, Voltage method: none\n");
+	printk(KERN_INFO "Low: %d Mhz, High: %d Mhz, Cur: %d MHz\n",
+		maple_cpu_freqs[1].frequency/1000,
+		maple_cpu_freqs[0].frequency/1000,
+		maple_cpu_freqs[maple_pmode_cur].frequency/1000);
+
+	rc = cpufreq_register_driver(&maple_cpufreq_driver);
+
+	of_node_put(cpunode);
+	of_node_put(cpus);
+
+	return rc;
+
+bail_noprops:
+	of_node_put(cpunode);
+bail_cpus:
+	of_node_put(cpus);
+
+	return rc;
+}
+
+module_init(maple_cpufreq_init);
+
+
+MODULE_LICENSE("GPL");
-- 
1.7.5.3