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[CPUFREQ] allow ondemand and conservative cpufreq governors to be used as default

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Depending on the transition latency of the HW for cpufreq switches, the
ondemand or conservative governor cannot be used with certain cpufreq
drivers.  Still the ondemand should be the default governor on a wide range
of systems.  This patch allows this and lets the governor fallback to the
performance governor at cpufreq driver load time, if the driver does not
support fast enough frequency switching.

Main benefit is that on e.g.  installation or other systems without
userspace support a working dynamic cpufreq support can be achieved on most
systems by simply loading the cpufreq driver.  This is especially essential
for recent x86(_64) laptop hardware which may rely on working dynamic
cpufreq OS support.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>
This commit is contained in:
Thomas Renninger
2007-10-02 13:28:12 -07:00
committed by Dave Jones
parent 8122c6cea0
commit 1c2562459f
5 changed files with 70 additions and 30 deletions
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12
drivers/cpufreq/cpufreq.c
View File

@@ -1484,6 +1484,18 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
unsigned int event)
{
int ret;
struct cpufreq_governor *gov = CPUFREQ_PERFORMANCE_GOVERNOR;
if (policy->governor->max_transition_latency &&
policy->cpuinfo.transition_latency >
policy->governor->max_transition_latency) {
printk(KERN_WARNING "%s governor failed, too long"
" transition latency of HW, fallback"
" to %s governor\n",
policy->governor->name,
gov->name);
policy->governor = gov;
}
if (!try_module_get(policy->governor->owner))
return -EINVAL;