On Thu, Aug 08, 2019 at 05:29:24PM +0200, Ulf Hansson wrote:

On Thu, 8 Aug 2019 at 14:55, Sudeep Holla [off-list ref] wrote:

quoted

On Mon, Jul 22, 2019 at 04:37:45PM +0100, Lorenzo Pieralisi wrote:

quoted

Current PSCI code handles idle state entry through the
psci_cpu_suspend_enter() API, that takes an idle state index as a
parameter and convert the index into a previously initialized
power_state parameter before calling the PSCI.CPU_SUSPEND() with it.

This is unwieldly, since it forces the PSCI firmware layer to keep track
of power_state parameter for every idle state so that the
index->power_state conversion can be made in the PSCI firmware layer
instead of the CPUidle driver implementations.

Move the power_state handling out of drivers/firmware/psci
into the respective ACPI/DT PSCI CPUidle backends and convert
the psci_cpu_suspend_enter() API to get the power_state
parameter as input, which makes it closer to its firmware
interface PSCI.CPU_SUSPEND() API.

A notable side effect is that the PSCI ACPI/DT CPUidle backends
now can directly handle (and if needed update) power_state
parameters before handing them over to the PSCI firmware
interface to trigger PSCI.CPU_SUSPEND() calls.

Signed-off-by: Lorenzo Pieralisi <redacted>
Cc: Will Deacon <will@kernel.org>
Cc: Ulf Hansson <redacted>
Cc: Sudeep Holla <redacted>

Reviewed-by: Sudeep Holla <redacted>

quoted

+static __init int psci_cpu_init_idle(unsigned int cpu)
+{
+     struct device_node *cpu_node;
+     int ret;
+
+     /*
+      * If the PSCI cpu_suspend function hook has not been initialized
+      * idle states must not be enabled, so bail out
+      */
+     if (!psci_ops.cpu_suspend)
+             return -EOPNOTSUPP;
+
+     cpu_node = of_get_cpu_node(cpu, NULL);

[nit] You could use of_cpu_device_node_get in linux/of_device.h as
it may avoid parsing if used later during the boot(i.e. after
cpu->of_node is populated). I think there's another instance in
psci_idle_init_cpu

Good idea!

However, as $subject patch more or less just moves code from the
current psci firmware directory into cpuidle, perhaps it's better to
defer improvements to be made on top?

I am fine either way. But since cpuidle-psci.c is new file introduced
in this series, we can have it as part of the original patch. I leave it
to Lorenzo to decide :)

--
Regards,
Sudeep