[PATCH] cpufrequency change on AC-Adapter Event

[PATCH] cpufrequency change on AC-Adapter Event

[Thomas Ogrisegg]

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Problem Description:
Whenever the status of the AC-Adapter on my laptop changes, the CPU
frequency automatically changes as well. For example, if the AC adapter
is online my CPU has the highest frequency (3,06 GHz). When the adapter
is unplugged, the frequency automatically decreases to 1,6 GHz. However,
currently the Kernel simply doesn't notice. It looks like the system is
still running at 3,06 GHz (/proc/cpuinfo and
/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq both show that),
but it doesn't like a simple test program showed.

My patch solves this problem: Whenever the status of the AC Adapter
changes, it calls 'cpufreq_reinit' which in turn reinits the CPUfreq
driver.

This, of course, only works if the ACPI AC driver is compiled in.

Signed-off-by: Thomas Ogrisegg <tom-lkml@lkml.fnord.at>

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diff -uNr -X linux-2.6.15/Documentation/dontdiff linux-2.6.15/drivers/acpi/ac.c linux-2.6.15.4/drivers/acpi/ac.c
--- linux-2.6.15/drivers/acpi/ac.c	2006-01-03 04:21:10.000000000 +0100
+++ linux-2.6.15.4/drivers/acpi/ac.c	2006-02-19 17:50:20.000000000 +0100
@@ -29,6 +29,7 @@
 #include <linux/types.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/cpufreq.h>
 #include <acpi/acpi_bus.h>
 #include <acpi/acpi_drivers.h>
 
@@ -213,6 +214,8 @@
 		break;
 	}
 
+	cpufreq_reinit();
+
 	return_VOID;
 }
 
diff -uNr -X linux-2.6.15/Documentation/dontdiff linux-2.6.15/drivers/cpufreq/cpufreq.c linux-2.6.15.4/drivers/cpufreq/cpufreq.c
--- linux-2.6.15/drivers/cpufreq/cpufreq.c	2006-01-03 04:21:10.000000000 +0100
+++ linux-2.6.15.4/drivers/cpufreq/cpufreq.c	2006-02-21 20:00:06.000000000 +0100
@@ -863,6 +863,30 @@
 
 
 /**
+ * cpufreq_reinit - reinitialize CPU frequency of all CPUs
+ */
+
+int cpufreq_reinit(void)
+{
+	int cpu, ret;
+	struct cpufreq_policy *policy;
+
+	for_each_online_cpu (cpu) {
+		policy = cpufreq_cpu_get(cpu);
+		if (!policy)
+			return -EINVAL;
+		ret = cpufreq_driver->exit(policy);
+		if (ret)
+			return ret;
+		ret = cpufreq_driver->init(policy);
+		if (ret)
+			return ret;
+	}
+	return (0);
+}
+EXPORT_SYMBOL(cpufreq_reinit);
+
+/**
  *	cpufreq_suspend - let the low level driver prepare for suspend
  */
 
--- linux-2.6.15/include/linux/cpufreq.h	2006-01-03 04:21:10.000000000 +0100
+++ linux-2.6.15.4/include/linux/cpufreq.h	2006-02-21 20:37:27.000000000 +0100
@@ -256,6 +256,11 @@
 /* query the current CPU frequency (in kHz). If zero, cpufreq couldn't detect it */
 unsigned int cpufreq_get(unsigned int cpu);
 
+#ifdef CONFIG_CPU_FREQ
+int cpu_freq_reinit(void);
+#else
+static inline int cpu_freq_reinit(void) { return 0; }
+#endif
 
 /*********************************************************************
  *                       CPUFREQ DEFAULT GOVERNOR                    *

Re: [PATCH] cpufrequency change on AC-Adapter Event

[Dominik Brodowski]

On Tue, Feb 21, 2006 at 10:37:42PM +0100, Thomas Ogrisegg wrote:
> Problem Description:
> Whenever the status of the AC-Adapter on my laptop changes, the CPU
> frequency automatically changes as well. For example, if the AC adapter
> is online my CPU has the highest frequency (3,06 GHz). When the adapter
> is unplugged, the frequency automatically decreases to 1,6 GHz. However,
> currently the Kernel simply doesn't notice. It looks like the system is
> still running at 3,06 GHz (/proc/cpuinfo and
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq both show that),
> but it doesn't like a simple test program showed.
> 
> My patch solves this problem: Whenever the status of the AC Adapter
> changes, it calls 'cpufreq_reinit' which in turn reinits the CPUfreq
> driver.
> 
> This, of course, only works if the ACPI AC driver is compiled in.

Uh, no, this just wraps band-aid around the problem. First of all, not all
cpufreq drivers like to be left and re-initialized. Secondly, the timing
code might still not adapt to the new CPU frequency. And thirdly, we can
solve these issues if we call


> 
> Signed-off-by: Thomas Ogrisegg <tom-lkml@lkml.fnord.at>

> diff -uNr -X linux-2.6.15/Documentation/dontdiff linux-2.6.15/drivers/acpi/ac.c linux-2.6.15.4/drivers/acpi/ac.c
> --- linux-2.6.15/drivers/acpi/ac.c	2006-01-03 04:21:10.000000000 +0100
> +++ linux-2.6.15.4/drivers/acpi/ac.c	2006-02-19 17:50:20.000000000 +0100
> @@ -29,6 +29,7 @@
>  #include <linux/types.h>
>  #include <linux/proc_fs.h>
>  #include <linux/seq_file.h>
> +#include <linux/cpufreq.h>
>  #include <acpi/acpi_bus.h>
>  #include <acpi/acpi_drivers.h>
>  
> @@ -213,6 +214,8 @@
>  		break;
>  	}
>  
> +	cpufreq_reinit();

	cpufreq_update_policy();

here instead. (untested, but should work)

Thanks,
	Dominik

Re: [PATCH] cpufrequency change on AC-Adapter Event

[Pavel Machek]

On Út 21-02-06 22:37:42, Thomas Ogrisegg wrote:
> Problem Description:
> Whenever the status of the AC-Adapter on my laptop changes, the CPU
> frequency automatically changes as well. For example, if the AC adapter
> is online my CPU has the highest frequency (3,06 GHz). When the adapter
> is unplugged, the frequency automatically decreases to 1,6 GHz. However,
> currently the Kernel simply doesn't notice. It looks like the system is
> still running at 3,06 GHz (/proc/cpuinfo and
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq both show that),
> but it doesn't like a simple test program showed.
> 
> My patch solves this problem: Whenever the status of the AC Adapter
> changes, it calls 'cpufreq_reinit' which in turn reinits the CPUfreq
> driver.
> 
> This, of course, only works if the ACPI AC driver is compiled in.
> 
> Signed-off-by: Thomas Ogrisegg <tom-lkml@lkml.fnord.at>

> diff -uNr -X linux-2.6.15/Documentation/dontdiff linux-2.6.15/drivers/acpi/ac.c linux-2.6.15.4/drivers/acpi/ac.c
> --- linux-2.6.15/drivers/acpi/ac.c	2006-01-03 04:21:10.000000000 +0100
> +++ linux-2.6.15.4/drivers/acpi/ac.c	2006-02-19 17:50:20.000000000 +0100
> @@ -29,6 +29,7 @@
>  #include <linux/types.h>
>  #include <linux/proc_fs.h>
>  #include <linux/seq_file.h>
> +#include <linux/cpufreq.h>
>  #include <acpi/acpi_bus.h>
>  #include <acpi/acpi_drivers.h>
>  
> @@ -213,6 +214,8 @@
>  		break;
>  	}
>  
> +	cpufreq_reinit();
> +
>  	return_VOID;
>  }
>  

Perhaps we need to call some notifier chain here? I think not only
cpufreq is going to be interested...
								Pavel

-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...