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Fwd: [loongson2-PATCH] modification of the cpufreq module

To: Ralf Baechle <ralf@linux-mips.org>, Dave Jones <davej@redhat.com>, Gang Liang <randomizedthinking@gmail.com>
Subject: Fwd: [loongson2-PATCH] modification of the cpufreq module
From: wu zhangjin <wuzhangjin@gmail.com>
Date: Wed, 2 Jun 2010 17:06:23 +0800
Cc: loongson-dev@googlegroups.com, Hua Yan <yanh@lemote.com>, linux-mips <linux-mips@linux-mips.org>, cpufreq@vger.kernel.org
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---------- Forwarded message ----------
From: Gang Liang <randomizedthinking@gmail.com>
Date: Wed, Jun 2, 2010 at 4:48 PM
Subject: [loongson2-PATCH] modification of the cpufreq module
To: linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>, Hua Yan <yanh@lemote.com>


This patch updates some aspects of the current implementation of
cpufreq driver for Loongson2.

1) A default cpu_wait handler is installed such that the cpu will be
alive at the lowest possible power level when a cpu_wait call is made;

2) The number of frequency levels is reduced to 3, and the lowest
frequency is capped as a half of the full cpu speed. The "nowait" option
is removed.

Thanks!

---
 arch/mips/include/asm/mach-loongson/loongson.h |    4 +-
 arch/mips/kernel/cpu-probe.c                   |   21 +++++++++
 arch/mips/kernel/cpufreq/loongson2_clock.c     |   52 +++--------------------
 arch/mips/kernel/cpufreq/loongson2_cpufreq.c   |   54 +++++++++---------------
 4 files changed, 50 insertions(+), 81 deletions(-)

diff --git a/arch/mips/include/asm/mach-loongson/loongson.h
b/arch/mips/include/asm/mach-loongson/loongson.h
index 53d0bef..33164b9 100644
--- a/arch/mips/include/asm/mach-loongson/loongson.h
+++ b/arch/mips/include/asm/mach-loongson/loongson.h
@@ -242,8 +242,8 @@ extern int mach_i8259_irq(void);

 #ifdef CONFIG_CPU_SUPPORTS_CPUFREQ
 #include <linux/cpufreq.h>
-extern void loongson2_cpu_wait(void);
-extern struct cpufreq_frequency_table loongson2_clockmod_table[];
+/* extern void loongson2_cpu_wait(void); */
+/* extern struct cpufreq_frequency_table loongson2_clockmod_table[]; */

 /* Chip Config */
 #define LOONGSON_CHIPCFG0              LOONGSON_REG(LOONGSON_REGBASE + 0x80)
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index be5bb16..5b3072c 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -25,6 +25,9 @@
 #include <asm/system.h>
 #include <asm/watch.h>
 #include <asm/spram.h>
+
+#include <loongson.h>
+
 /*
 * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
 * the implementation of the "wait" feature differs between CPU families. This
@@ -51,6 +54,21 @@ static void r39xx_wait(void)

 extern void r4k_wait(void);

+DEFINE_SPINLOCK(loongson2_wait_lock);
+static void loongson2_cpu_wait(void)
+{
+    u32 cpu_freq;
+    unsigned long flags;
+
+    /* enter the lowest power mode available while still alive */
+    /* future work: check cpu freq -- do nothing if no change */
+    /* otherwise, change the frequency and propagate the clock rate */
+    spin_lock_irqsave(&loongson2_wait_lock, flags);
+    cpu_freq = LOONGSON_CHIPCFG0;
+       LOONGSON_CHIPCFG0 = (cpu_freq & ~0x7) | 1;
+    spin_unlock_irqrestore(&loongson2_wait_lock, flags);
+}
+
 /*
 * This variant is preferable as it allows testing need_resched and going to
 * sleep depending on the outcome atomically.  Unfortunately the "It is
@@ -212,6 +230,9 @@ void __init check_wait(void)
               if ((c->processor_id & 0x00ff) >= 0x40)
                       cpu_wait = r4k_wait;
               break;
+    case CPU_LOONGSON2:
+        cpu_wait = loongson2_cpu_wait;
+        break;
       default:
               break;
       }
diff --git a/arch/mips/kernel/cpufreq/loongson2_clock.c
b/arch/mips/kernel/cpufreq/loongson2_clock.c
index cefc6e2..0b30fe9 100644
--- a/arch/mips/kernel/cpufreq/loongson2_clock.c
+++ b/arch/mips/kernel/cpufreq/loongson2_clock.c
@@ -18,25 +18,7 @@ static LIST_HEAD(clock_list);
 static DEFINE_SPINLOCK(clock_lock);
 static DEFINE_MUTEX(clock_list_sem);

-/* Minimum CLK support */
-enum {
-       DC_ZERO, DC_25PT = 2, DC_37PT, DC_50PT, DC_62PT, DC_75PT,
-       DC_87PT, DC_DISABLE, DC_RESV
-};
-
-struct cpufreq_frequency_table loongson2_clockmod_table[] = {
-       {DC_RESV, CPUFREQ_ENTRY_INVALID},
-       {DC_ZERO, CPUFREQ_ENTRY_INVALID},
-       {DC_25PT, 0},
-       {DC_37PT, 0},
-       {DC_50PT, 0},
-       {DC_62PT, 0},
-       {DC_75PT, 0},
-       {DC_87PT, 0},
-       {DC_DISABLE, 0},
-       {DC_RESV, CPUFREQ_TABLE_END},
-};
-EXPORT_SYMBOL_GPL(loongson2_clockmod_table);
+#define LS2_MAX_CPUFREQ_LEVEL 8

 static struct clk cpu_clk = {
       .name = "cpu_clk",
@@ -109,21 +91,15 @@ int clk_set_rate_ex(struct clk *clk, unsigned
long rate, int algo_id)
       if (unlikely(clk->flags & CLK_RATE_PROPAGATES))
               propagate_rate(clk);

-       for (i = 0; loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END;
-            i++) {
-               if (loongson2_clockmod_table[i].frequency ==
-                   CPUFREQ_ENTRY_INVALID)
-                       continue;
-               if (rate == loongson2_clockmod_table[i].frequency)
-                       break;
-       }
-       if (rate != loongson2_clockmod_table[i].frequency)
-               return -ENOTSUPP;
+    i = rate * LS2_MAX_CPUFREQ_LEVEL / cpu_clock_freq;
+    if ( i < 1 || i > LS2_MAX_CPUFREQ_LEVEL )
+        return -ENOTSUPP;

-       clk->rate = rate;
+    /* indeed, a rounded rate is assigned */
+       clk->rate = i * (cpu_clock_freq / LS2_MAX_CPUFREQ_LEVEL);

       regval = LOONGSON_CHIPCFG0;
-       regval = (regval & ~0x7) | (loongson2_clockmod_table[i].index - 1);
+       regval = (regval & ~0x7) | i;
       LOONGSON_CHIPCFG0 = regval;

       return ret;
@@ -151,20 +127,6 @@ EXPORT_SYMBOL_GPL(clk_round_rate);
 * interrupt disabled content
 */

-DEFINE_SPINLOCK(loongson2_wait_lock);
-void loongson2_cpu_wait(void)
-{
-       u32 cpu_freq;
-       unsigned long flags;
-
-       spin_lock_irqsave(&loongson2_wait_lock, flags);
-       cpu_freq = LOONGSON_CHIPCFG0;
-       LOONGSON_CHIPCFG0 &= ~0x7;      /* Put CPU into wait mode */
-       LOONGSON_CHIPCFG0 = cpu_freq;   /* Restore CPU state */
-       spin_unlock_irqrestore(&loongson2_wait_lock, flags);
-}
-EXPORT_SYMBOL_GPL(loongson2_cpu_wait);
-
 MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
 MODULE_DESCRIPTION("cpufreq driver for Loongson 2F");
 MODULE_LICENSE("GPL");
diff --git a/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
b/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
index 2f6a0b1..0488945 100644
--- a/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
+++ b/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
@@ -21,11 +21,16 @@

 #include <loongson.h>

-static uint nowait;
+#define LS2_CPUFREQ_LEVEL 3

 static struct clk *cpuclk;

-static void (*saved_cpu_wait) (void);
+struct cpufreq_frequency_table loongson2_clockmod_table[] = {
+       {0, 0},
+       {1, 0},
+       {2, 0},
+       { .frequency = CPUFREQ_TABLE_END },
+};

 static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
                                       unsigned long val, void *data);
@@ -67,14 +72,11 @@ static int loongson2_cpufreq_target(struct
cpufreq_policy *policy,
       cpus_allowed = current->cpus_allowed;
       set_cpus_allowed(current, cpumask_of_cpu(cpu));

-       if (cpufreq_frequency_table_target
-           (policy, &loongson2_clockmod_table[0], target_freq, relation,
-            &newstate))
+       if (cpufreq_frequency_table_target (policy,
+                       &loongson2_clockmod_table[0], target_freq,
relation, &newstate))
               return -EINVAL;

-       freq =
-           ((cpu_clock_freq / 1000) *
-            loongson2_clockmod_table[newstate].index) / 8;
+       freq = loongson2_clockmod_table[newstate].frequency;
       if (freq < policy->min || freq > policy->max)
               return -EINVAL;

@@ -88,15 +90,10 @@ static int loongson2_cpufreq_target(struct
cpufreq_policy *policy,
       if (freqs.new == freqs.old)
               return 0;

-       /* notifiers */
+       /* change cpu clock between notifier pairs */
       cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
-
       set_cpus_allowed(current, cpus_allowed);
-
-       /* setting the cpu frequency */
       clk_set_rate(cpuclk, freq);
-
-       /* notifiers */
       cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

       pr_debug("cpufreq: set frequency %u kHz\n", freq);
@@ -121,11 +118,12 @@ static int loongson2_cpufreq_cpu_init(struct
cpufreq_policy *policy)
       if (!cpuclk->rate)
               return -EINVAL;

-       /* clock table init */
-       for (i = 2;
-            (loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END);
-            i++)
-               loongson2_clockmod_table[i].frequency = (cpuclk->rate * i) / 8;
+       /* initialize the clock table such that all frequencies */
+       /* evenly span within [cpu_clock_freq/2, cpu_clock_freq] */
+       for (i = 0; i < LS2_CPUFREQ_LEVEL; i++) {
+               loongson2_clockmod_table[i].frequency = cpuclk->rate *
+                       (i+LS2_CPUFREQ_LEVEL-1) / (2*LS2_CPUFREQ_LEVEL-2);
+    }

       policy->cur = loongson2_cpufreq_get(policy->cpu);

@@ -139,7 +137,7 @@ static int loongson2_cpufreq_cpu_init(struct
cpufreq_policy *policy)
 static int loongson2_cpufreq_verify(struct cpufreq_policy *policy)
 {
       return cpufreq_frequency_table_verify(policy,
-                                             &loongson2_clockmod_table[0]);
+                                       &loongson2_clockmod_table[0]);
 }

 static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
@@ -185,7 +183,7 @@ static int __init cpufreq_init(void)
 {
       int ret;

-       /* Register platform stuff */
+       /* Register platform driver */
       ret = platform_driver_register(&platform_driver);
       if (ret)
               return ret;
@@ -195,20 +193,11 @@ static int __init cpufreq_init(void)
       cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
                                 CPUFREQ_TRANSITION_NOTIFIER);

-       ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
-
-       if (!ret && !nowait) {
-               saved_cpu_wait = cpu_wait;
-               cpu_wait = loongson2_cpu_wait;
-       }
-
-       return ret;
+       return cpufreq_register_driver(&loongson2_cpufreq_driver);
 }

 static void __exit cpufreq_exit(void)
 {
-       if (!nowait && saved_cpu_wait)
-               cpu_wait = saved_cpu_wait;
       cpufreq_unregister_driver(&loongson2_cpufreq_driver);
       cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
                                   CPUFREQ_TRANSITION_NOTIFIER);
@@ -219,9 +208,6 @@ static void __exit cpufreq_exit(void)
 module_init(cpufreq_init);
 module_exit(cpufreq_exit);

-module_param(nowait, uint, 0644);
-MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
-
 MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
 MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
 MODULE_LICENSE("GPL");



--
Gang Liang
Life is beautiful!

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