[ARM] OMAP2: Implement CPUfreq frequency table based on PRCM table

This patch adds a CPUfreq frequency-table implementation for OMAP2 by
walking the PRCM rate-table for available entries and adding them to a
CPUfreq table.

CPUfreq can then be used to manage switching between all the available
entries in the PRCM rate table.  Either use the CPUfreq sysfs
interface directly, (see Section 3 of Documentation/cpu-freq/user-guide.txt)
or use the cpufrequtils package:
http://www.kernel.org/pub/linux/utils/kernel/cpufreq/cpufrequtils.html

Signed-off-by: Kevin Hilman <khilman@mvista.com>

Updated to try to use cpufreq_table if it exists.

linux-omap source commit is 77ce544fa48deb7a2003f454624e3ca10d37ab87.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 53 insertions, 4 deletions

diff --git a/arch/arm/plat-omap/cpu-omap.c b/arch/arm/plat-omap/cpu-omap.c
index b2690242a390..843e8af64066 100644
--- a/arch/arm/plat-omap/cpu-omap.c
+++ b/arch/arm/plat-omap/cpu-omap.c
@@ -23,10 +23,13 @@
 #include <linux/io.h>
 
 #include <mach/hardware.h>
+#include <mach/clock.h>
 #include <asm/system.h>
 
 #define VERY_HI_RATE    900000000
 
+static struct cpufreq_frequency_table *freq_table;
+
 #ifdef CONFIG_ARCH_OMAP1
 #define MPU_CLK         "mpu"
 #else
@@ -39,6 +42,9 @@ static struct clk *mpu_clk;
 
 int omap_verify_speed(struct cpufreq_policy *policy)
 {
+        if (freq_table)
+                return cpufreq_frequency_table_verify(policy, freq_table);
+
         if (policy->cpu)
                 return -EINVAL;
 
@@ -70,12 +76,26 @@ static int omap_target(struct cpufreq_policy *policy,
         struct cpufreq_freqs freqs;
         int ret = 0;
 
+        /* Ensure desired rate is within allowed range.  Some govenors
+         * (ondemand) will just pass target_freq=0 to get the minimum. */
+        if (target_freq < policy->cpuinfo.min_freq)
+                target_freq = policy->cpuinfo.min_freq;
+        if (target_freq > policy->cpuinfo.max_freq)
+                target_freq = policy->cpuinfo.max_freq;
+
         freqs.old = omap_getspeed(0);
         freqs.new = clk_round_rate(mpu_clk, target_freq * 1000) / 1000;
         freqs.cpu = 0;
 
+        if (freqs.old == freqs.new)
+                return ret;
+
         cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
-        ret = clk_set_rate(mpu_clk, target_freq * 1000);
+#ifdef CONFIG_CPU_FREQ_DEBUG
+        printk(KERN_DEBUG "cpufreq-omap: transition: %u --> %u\n",
+               freqs.old, freqs.new);
+#endif
+        ret = clk_set_rate(mpu_clk, freqs.new * 1000);
         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
 
         return ret;
@@ -83,16 +103,31 @@ static int omap_target(struct cpufreq_policy *policy,
 
 static int __init omap_cpu_init(struct cpufreq_policy *policy)
 {
+        int result = 0;
+
         mpu_clk = clk_get(NULL, MPU_CLK);
         if (IS_ERR(mpu_clk))
                 return PTR_ERR(mpu_clk);
 
         if (policy->cpu != 0)
                 return -EINVAL;
+
         policy->cur = policy->min = policy->max = omap_getspeed(0);
-        policy->cpuinfo.min_freq = clk_round_rate(mpu_clk, 0) / 1000;
-        policy->cpuinfo.max_freq = clk_round_rate(mpu_clk, VERY_HI_RATE) / 1000;
-        policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
+
+        clk_init_cpufreq_table(&freq_table);
+        if (freq_table) {
+                result = cpufreq_frequency_table_cpuinfo(policy, freq_table);
+                if (!result)
+                        cpufreq_frequency_table_get_attr(freq_table,
+                                                        policy->cpu);
+        } else {
+                policy->cpuinfo.min_freq = clk_round_rate(mpu_clk, 0) / 1000;
+                policy->cpuinfo.max_freq = clk_round_rate(mpu_clk,
+                                                        VERY_HI_RATE) / 1000;
+        }
+
+        /* FIXME: what's the actual transition time? */
+        policy->cpuinfo.transition_latency = 10 * 1000 * 1000;
 
         return 0;
 }
@@ -103,6 +138,11 @@ static int omap_cpu_exit(struct cpufreq_policy *policy)
         return 0;
 }
 
+static struct freq_attr *omap_cpufreq_attr[] = {
+        &cpufreq_freq_attr_scaling_available_freqs,
+        NULL,
+};
+
 static struct cpufreq_driver omap_driver = {
         .flags          = CPUFREQ_STICKY,
         .verify         = omap_verify_speed,
@@ -111,6 +151,7 @@ static struct cpufreq_driver omap_driver = {
         .init           = omap_cpu_init,
         .exit           = omap_cpu_exit,
         .name           = "omap",
+        .attr           = omap_cpufreq_attr,
 };
 
 static int __init omap_cpufreq_init(void)
@@ -119,3 +160,11 @@ static int __init omap_cpufreq_init(void)
 }
 
 arch_initcall(omap_cpufreq_init);
+
+/*
+ * if ever we want to remove this, upon cleanup call:
+ *
+ * cpufreq_unregister_driver()
+ * cpufreq_frequency_table_put_attr()
+ */
+