[PATCH v4 4/5] arm64: add support for ACPI Low Power Idle(LPI)

On 20/04/16 10:59, Vikas Sajjan wrote:

Hi Sudeep,

On Tue, Apr 19, 2016 at 6:00 PM, Sudeep Holla [off-list ref] wrote:

quoted

This patch adds appropriate callbacks to support ACPI Low Power Idle
(LPI) on ARM64.

It also selects ARCH_SUPPORTS_ACPI_PROCESSOR_LPI if ACPI is enabled
on ARM64.

[...]

quoted

@@ -211,6 +214,37 @@ void __init acpi_boot_table_init(void)
         }
  }

+int acpi_processor_ffh_lpi_probe(unsigned int cpu)
+{
+       return arm_cpuidle_init(cpu);
+}
+

This is generating warning as below:

WARNING: vmlinux.o(.text+0x11024): Section mismatch in reference from
the function acpi_processor_ffh_lpi_probe() to the function
.init.text:arm_cpuidle_init()
The function acpi_processor_ffh_lpi_probe() references
the function __init arm_cpuidle_init().
This is often because acpi_processor_ffh_lpi_probe lacks a __init
annotation or the annotation of arm_cpuidle_init is wrong.

I am aware of this and needs to be fixed. I posted ARM64/PSCI related
patches for completeness.

We can't have __init annotation for ..ffh_lpi_probe as it can be called
from hotplug paths in ACPI. Only solution I see is to remove __init tag
for arm_cpuidle_init. I raised similar concern on the other thread
yesterday[1]

Thanks for looking at these patches, much appreciated.

quoted

+struct acpi_processor_lpi *lpi;
+int acpi_processor_ffh_lpi_enter(struct acpi_processor_lpi *lpi, int idx)

Wondering how are you handling with Resource Dependencies for Idle.
I mean _RDI needs to be taken care, since the dependency between the
power resources and the LPI state is described in _RDI.

Correct, right now I haven't considered RDI yet as I don't have proper
platform to test. IMO it can be added later as RDI is optional and not
used on all platforms.

-- 
Regards,
Sudeep

[1] http://lkml.iu.edu/hypermail/linux/kernel/1604.2/02181.html