linux-kernel - Re: v5.7: new core kernel option missing help text

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Date:   Thu, 04 Jun 2020 16:38:40 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: v5.7: new core kernel option missing help text


On 04/06/20 14:05, Thara Gopinath wrote:
> On Thu, 4 Jun 2020 at 06:56, Valentin Schneider <valentin.schneider@....com>
>>
>> Right, s/defconfig/arch kconfig/ or somesuch.
>>
>
>  CPU_FREQ_THERMAL also has to be enabled for this to be effective.
> Since arm64 defconfig enables  CPU_FREQ_THERMAL  (by enabling CPU_THERMAL),
> it should be ok to enable it in arm64/Kconfig. (same with arm/Kconfig)
>
> Another option is to select the  SCHED_THERMAL_PRESSURE when
> CPU_FREQ_THERMAL
> is enabled in drivers/thermal/Kconfig.
>

So interestingly while arch_set_thermal_pressure() (which just writes to a
pcpu variable) is defined in sched/core.c, arch_scale_thermal_pressure()
(which just returns aforementionned pcpu variable) is defined in
arch_topology...

I'm thinking at this point we might as well turn the
arch_scale_thermal_pressure() stub into what arch_topology does. This would
effectively let any architecture use thermal pressure, providing they use
cpufreq cooling.

If we want to keep changes contained to Kconfigs, for now I think the
safest would be:

---
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 16fbf74030fe..1e92080dc275 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -46,6 +46,7 @@ config ARM
        select EDAC_ATOMIC_SCRUB
        select GENERIC_ALLOCATOR
        select GENERIC_ARCH_TOPOLOGY if ARM_CPU_TOPOLOGY
+	select SCHED_THERMAL_PRESSURE if GENERIC_ARCH_TOPOLOGY
        select GENERIC_ATOMIC64 if CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI
        select GENERIC_CLOCKEVENTS_BROADCAST if SMP
        select GENERIC_CPU_AUTOPROBE
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 552d36cacc05..cc1944fbae51 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -98,6 +98,7 @@ config ARM64
        select FRAME_POINTER
        select GENERIC_ALLOCATOR
        select GENERIC_ARCH_TOPOLOGY
+	select SCHED_THERMAL_PRESSURE
        select GENERIC_CLOCKEVENTS
        select GENERIC_CLOCKEVENTS_BROADCAST
        select GENERIC_CPU_AUTOPROBE
diff --git a/init/Kconfig b/init/Kconfig
index 74a5ac65644f..ba846f6e805b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -439,8 +439,11 @@ config HAVE_SCHED_AVG_IRQ
        depends on SMP

 config SCHED_THERMAL_PRESSURE
-	bool "Enable periodic averaging of thermal pressure"
+	def_bool n
        depends on SMP
+	depends on CPU_FREQ_THERMAL
+	help
+	  <helpful thing here>

 config BSD_PROCESS_ACCT
        bool "BSD Process Accounting"
---



> Warm Regards
> Thara