On 04/10/2013 08:22 PM, Colin Cross wrote:
On Wed, Apr 10, 2013 at 7:22 AM, Daniel Lezcano daniel.lezcano@linaro.org wrote:
The usual scheme to initialize a cpuidle driver on a SMP is:
cpuidle_register_driver(drv); for_each_possible_cpu(cpu) { device = &per_cpu(cpuidle_dev, cpu); cpuidle_register_device(device); }This code is duplicated in each cpuidle driver.
On UP systems, it is done this way:
cpuidle_register_driver(drv); device = &per_cpu(cpuidle_dev, cpu); cpuidle_register_device(device);On UP, the macro 'for_each_cpu' does one iteration:
#define for_each_cpu(cpu, mask) \ for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
Hence, the initialization loop is the same for UP than SMP.
Beside, we saw different bugs / mis-initialization / return code unchecked in the different drivers, the code is duplicated including bugs. After fixing all these ones, it appears the initialization pattern is the same for everyone.
Let's add a wrapper function doing this initialization with a cpumask parameter for the coupled idle states and use it for all the drivers.
Isn't this going to cause problems for big.LITTLE, which has two independent sets of coupled cpus, and may even have different drivers for the two types of cpu?
AFAICT no, because the "low levels" API are still there, I mean cpuidle_register_driver and cpuidle_register_device. That will be up to the b.L driver to use the API which fits its need.