Re: [PATCH v2 2/2] pm: cpupower: Makefile: Allow overriding cross-compiling env params

[Florian Fainelli <florian.fainelli@broadcom.com>]

On 11/21/24 04:40, Peng Fan wrote:
>> Subject: Re: [PATCH v2 2/2] pm: cpupower: Makefile: Allow overriding
>> cross-compiling env params
>>
>> Hi Peng,
>>
>> On 9/19/2024 5:08 AM, Peng Fan (OSS) wrote:
>>> From: Peng Fan <peng.fan@nxp.com>
>>>
>>> Allow overriding the cross-comple env parameters to make it easier
>> for
>>> Yocto users. Then cross-compiler toolchains to build cpupower with
>>> only two steps:
>>> - source (toolchain path)/environment-setup-armv8a-poky-linux
>>> - make
>>
>> This patch breaks the way that buildroot builds cpupower:
>>
>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
>> git.buildroot.net%2Fbuildroot%2Ftree%2Fpackage%2Flinux-
>> tools%2Flinux-tool-
>> cpupower.mk.in&data=05%7C02%7Cpeng.fan%40nxp.com%7C246da9
>> 2d8b6243d138c808dd09e6d644%7C686ea1d3bc2b4c6fa92cd99c5c3
>> 01635%7C0%7C0%7C638677609234547728%7CUnknown%7CTWFpb
>> GZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJX
>> aW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdat
>> a=nL1YUl%2F07Vd8F0GpW7uRqdpZT74avOku1ox9N3%2FFkUg%3D&r
>> eserved=0
>>
>> and after enabling verbose it becomes clear as to why, see below:
>>
>>   >>> linux-tools  Configuring
>>   >>> linux-tools  Building
>> GIT_DIR=.
>> PATH="/local/users/fainelli/buildroot-
>> upstream/output/arm/host/bin:/local/users/fainelli/buildroot-
>> upstream/output/arm/host/sbin:/projects/firepath/tools/bin:/home/ff
>> 944844/bin:/home/ff944844/.local/bin:/opt/stblinux/bin:/usr/local/sb
>> in:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/ga
>> mes:/snap/bin:/opt/toolchains/metaware-vctools-0.4.1/bin/"
>> /usr/bin/make -j97
>> CROSS=/local/users/fainelli/buildroot-
>> upstream/output/arm/host/bin/arm-linux-
>> CPUFREQ_BENCH=false NLS=false LDFLAGS="-L.
>> -L/local/users/fainelli/buildroot-upstream/output/arm/target/usr/lib"
>> DEBUG=false V=1 -C
>> /local/users/fainelli/buildroot-upstream/output/arm/build/linux-
>> custom/tools
>> cpupower
>> mkdir -p power/cpupower && /usr/bin/make  subdir=power/cpupower
>> --no-print-directory -C power/cpupower cc -DVERSION=\"6.12.0\" -
>> DPACKAGE=\"cpupower\"
>> -DPACKAGE_BUGREPORT=\"linux-pm@vger.kernel.org\" -
>> D_GNU_SOURCE -pipe -Wall -Wchar-subscripts -Wpointer-arith -Wsign-
>> compare -Wno-pointer-sign -Wdeclaration-after-statement -Wshadow -
>> Os -fomit-frame-pointer -fPIC -o lib/cpufreq.o -c lib/cpufreq.c
> 
> You are building on an ARM host? Or you are cross compiling
> with cc is actually arm gcc?

This is cross compiling targeting ARM, which is why CROSS is set to 
../arm-linux-

> 
>>
>> Here we use cc, aka host compiler, rather than $(CROSS)gcc as we
>> should, so we are no longer cross compiling at all.
> 
> I not understand. CROSS was set, but using cc to compile for host?

See below.

> 
>>
>> The issue is the use of the lazy set if absent for *all* of CC, LD, AR, STRIP,
>> RANLIB, rather than just for CROSS. The following fixes it for me:
>>
>> diff --git a/tools/power/cpupower/Makefile
>> b/tools/power/cpupower/Makefile index
>> 175004ce44b2..96bb1e5f3970 100644
>> --- a/tools/power/cpupower/Makefile
>> +++ b/tools/power/cpupower/Makefile
>> @@ -87,11 +87,11 @@ INSTALL_SCRIPT = ${INSTALL} -m 644
>>    # to something more interesting, like "arm-linux-".  If you want
>>    # to compile vs uClibc, that can be done here as well.
>>    CROSS ?= #/usr/i386-linux-uclibc/usr/bin/i386-uclibc-
>> -CC ?= $(CROSS)gcc
>> -LD ?= $(CROSS)gcc
>> -AR ?= $(CROSS)ar
>> -STRIP ?= $(CROSS)strip
>> -RANLIB ?= $(CROSS)ranlib
>> +CC = $(CROSS)gcc
>> +LD = $(CROSS)gcc
>> +AR = $(CROSS)ar
>> +STRIP = $(CROSS)strip
>> +RANLIB = $(CROSS)ranlib
> 
> The ? is just allow to override CC/LD/AR.., so in your env,
> CC is set, but should not be used for cpupower compling?

Adding debug to show the origin of the CC variable shows the following:

CROSS=/local/users/fainelli/buildroot-upstream/output/arm/host/bin/arm-linux-
CC origin is (default) and value is (cc)
LD origin is (default) and value is (ld)
CC=cc
LD=ld
AR=ar
STRIP=
RANLIB=

See 
https://www.gnu.org/software/make/manual/html_node/Origin-Function.html#Origin-Function
-- 
Florian