[PATCH 1/2] drivers: psci: PSCI checker module

[Arnd Bergmann]

On Tuesday, November 8, 2016 5:55:46 PM CET Lorenzo Pieralisi wrote:
> From: Kevin Brodsky <kevin.brodsky at arm.com>
> 
> On arm and arm64, PSCI is one of the possible firmware interfaces
> used for power management. This includes both turning CPUs on and off,
> and suspending them (entering idle states).
> 
> This patch adds a PSCI checker module that enables basic testing of
> PSCI operations during startup. There are two main tests: CPU
> hotplugging and suspending.
> 
> In the hotplug tests, the hotplug API is used to turn off and on again
> all CPUs in the system, and then all CPUs in each cluster, checking
> the consistency of the return codes.
> 
> In the suspend tests, a high-priority thread is created on each core
> and uses low-level cpuidle functionalities to enter suspend, in all
> the possible states and multiple times. This should allow a maximum
> number of CPUs to enter the same sleep state at the same or slightly
> different time.
> 
> In essence, the suspend tests use a principle similar to that of the
> intel_powerclamp driver (drivers/thermal/intel_powerclamp.c), but the
> threads are only kept for the duration of the test (they are already
> gone when userspace is started) and it does not require to stop/start
> the tick.
> 
> While in theory power management PSCI functions (CPU_{ON,OFF,SUSPEND})
> could be directly called, this proved too difficult as it would imply
> the duplication of all the logic used by the kernel to allow for a
> clean shutdown/bringup/suspend of the CPU (the deepest sleep states
> implying potentially the shutdown of the CPU).
> 
> Note that this file cannot be compiled as a loadable module, since it
> uses a number of non-exported identifiers (essentially for
> PSCI-specific checks and direct use of cpuidle) and relies on the
> absence of userspace to avoid races when calling hotplug and cpuidle
> functions.
> 
> For now at least, CONFIG_PSCI_CHECKER is mutually exclusive with
> CONFIG_TORTURE_TEST, because torture tests may also use hotplug and
> cause false positives in the hotplug tests.
> 
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Kevin Hilman <khilman at kernel.org>
> Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
> Cc: James Morse <james.morse at arm.com>
> Cc: Sudeep Holla <sudeep.holla at arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Acked-by: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com> [torture test config]
> Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
> [lpieralisi: added cpuidle locking, reworded commit log/kconfig entry]
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>

Applied both patches to the next/drivers tree in arm-soc now, sorry
for the delay,

	Arnd