[PATCH v3 3/3] cpuidle: big.LITTLE: vexpress-TC2 CPU idle driver

[Lorenzo Pieralisi]

On Thu, Aug 08, 2013 at 05:00:24PM +0100, Daniel Lezcano wrote:
> On 08/07/2013 01:43 PM, Lorenzo Pieralisi wrote:
> > The big.LITTLE architecture is composed of two clusters of cpus. One cluster
> > contains less powerful but more energy efficient processors and the other
> > cluster groups the powerful but energy-intensive cpus.
> > 
> > The TC2 testchip implements two clusters of CPUs (A7 and A15 clusters in
> > a big.LITTLE configuration) connected through a CCI interconnect that manages
> > coherency of their respective L2 caches and intercluster distributed
> > virtual memory messages (DVM).
> > 
> > TC2 testchip integrates a power controller that manages cores resets, wake-up
> > IRQs and cluster low-power states. Power states are managed at cluster
> > level, which means that voltage is removed from a cluster iff all cores
> > in a cluster are in a wfi state. Single cores can enter a reset state
> > which is identical to wfi in terms of power consumption but simplifies the
> > way cluster states are entered.
> > 
> > This patch provides a multiple driver CPU idle implementation for TC2
> > which paves the way for a generic big.LITTLE idle driver for all
> > upcoming big.LITTLE based systems on chip.
> > 
> > The driver relies on the MCPM infrastructure to coordinate and manage
> > core power states; in particular MCPM allows to suspend specific cores
> > and hides the CPUs coordination required to shut-down clusters of CPUs.
> > 
> > Power down sequences for the respective clusters are implemented in the
> > MCPM TC2 backend, with all code needed to clean caches and exit coherency.
> > 
> > The multiple driver CPU idle infrastructure allows to define different
> > C-states for big and little cores, determined at boot by checking the
> > part id of the possible CPUs and initializing the respective logical
> > masks in the big and little drivers.
> > 
> > Current big.little systems are composed of A7 and A15 clusters, as
> > implemented in TC2, but in the future that may change and the driver
> > will have evolve to retrieve what is a 'big' cpu and what is a 'little'
> > cpu in order to build the correct topology.
> > 
> > Cc: Kevin Hilman <khilman at linaro.org>
> > Cc: Amit Kucheria <amit.kucheria at linaro.org>
> > Cc: Olof Johansson <olof at lixom.net>
> > Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
> > Cc: Rafael J. Wysocki <rjw at sisk.pl>
> > Signed-off-by: Daniel Lezcano <daniel.lezcano at linaro.org>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > ---
> 
> A nit below :/
> 
> [ ... ]
> 
> > +
> > +static struct cpuidle_driver bl_idle_big_driver = {
> > +	.name = "big_idle",
> > +	.owner = THIS_MODULE,
> > +	.states[0] = ARM_CPUIDLE_WFI_STATE,
> > +	.states[1] = {
> > +		.enter			= bl_enter_powerdown,
> > +
> > +		.exit_latency		= 500,
> 
> Extra line between enter and exit_latency.

Gah, not anymore :)

Other than that, is it ready to go ? If nobody complains I have planned
to send a pull request early next week, as soon as a stable branch for
TC2 MCPM gets in arm-soc.

Thanks,
Lorenzo