Re: [PATCH 4/4] cpuidle - support multiple drivers

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 10/04/2012 04:14 PM, Peter De Schrijver wrote:
> On Tue, Sep 25, 2012 at 12:43:54AM +0200, Daniel Lezcano wrote:
>> With the tegra3 and the big.LITTLE [1] new architectures, several cpus
>> with different characteristics (latencies and states) can co-exists on the
>> system.
>>
>> The cpuidle framework has the limitation of handling only identical cpus.
>>
>> This patch removes this limitation by introducing the multiple driver support
>> for cpuidle.
>>
>> This option is configurable at compile time and should be enabled for the
>> architectures mentioned above. So there is no impact for the other platforms
>> if the option is disabled. The option defaults to 'n'. Note the multiple drivers
>> support is also compatible with the existing drivers, even if just one driver is
>> needed, all the cpu will be tied to this driver using an extra small chunk of
>> processor memory.
>>
>> The multiple driver support use a per-cpu driver pointer instead of a global
>> variable and the accessor to this variable are done from a cpu context.
>>
>> In order to keep the compatibility with the existing drivers, the function
>> 'cpuidle_register_driver' and 'cpuidle_unregister_driver' will register
>> the specified driver for all the cpus.
>>
>> The sysfs output for the 'current_driver' is changed when this option is
>> set by giving the drivers per cpu.
>>
>> eg.
>> cpu0: acpi_idle
>> cpu1: acpi_idle
>>
> 
> Is this allowed? I thought sysfs files can output only 1 line of data?

Ah yeah :)

Does it make sense to put the following files:

/sys/devices/system/cpu/cpu0/cpuidle/driver
 => acpi_idle
/sys/devices/system/cpu/cpu1/cpuidle/driver
 => acpi_idle

and the content of the file:

/sys/devices/system/cpu/cpuidle/current_driver will show the driver
associated with current cpu ?


-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html