[Buildroot] SH4A target: error: command line option ‘-m4-nofpu’ is not supported by this configuration
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Fri Dec 2 20:31:22 UTC 2016
Hello,
On Fri, 2 Dec 2016 18:41:11 +0000, John Gulbrandsen wrote:
> I tried to manually edit ~buildroot/output/build/linux-4.7/.config :
>
> #
> # System type
> #
> #CONFIG_CPU_SH4=y
> CONFIG_CPU_SH4A=y
> #CONFIG_CPU_SHX3=y
>
> But this resulted in all four CPU types being put back by buildroot when doing 'make linux'.
>
> Why does buildroot force ' CONFIG_CPU_SH4' and ' CONFIG_CPU_SHX3' to be set?
It's not Buildroot who does that, but the Linux kernel.
You have select the SH7786 processor in your Linux kernel
configuration, through the option CPU_SUBTYPE_SH7786. This option is
defined as:
config CPU_SUBTYPE_SH7786
bool "Support SH7786 processor"
select CPU_SH4A
select CPU_SHX3
And then CPU_SH4A is defined as:
config CPU_SH4A
bool
select CPU_SH4
So, whenever you select SH7786, it is normal to have all of CPU_SHX3,
CPU_SH4 and CPU_SH4A enabled. And I believe the intent is that SH4A is
a super-set of SH4 and SHX3, which is why all of these are selected.
However, due to this, in arch/sh/Makefile, both of those lines get
enabled:
cflags-$(CONFIG_CPU_SH4) := $(call cc-option,-m4,) \
$(call cc-option,-mno-implicit-fp,-m4-nofpu)
cflags-$(CONFIG_CPU_SH4A) += $(call cc-option,-m4a,) \
$(call cc-option,-m4a-nofpu,)
So it means that the cc-option make function fails, because
-mno-implicit-fp is not supported, falls back to passing -m4-nofpu,
which we don't support in Buildroot when SH4A is selected at the
architecture variant.
All in all, I'm wondering if we shouldn't patch our gcc-final.mk as
follows:
diff --git a/package/gcc/gcc-final/gcc-final.mk b/package/gcc/gcc-final/gcc-final.mk
index c9ee476..4eab3f5 100644
--- a/package/gcc/gcc-final/gcc-final.mk
+++ b/package/gcc/gcc-final/gcc-final.mk
@@ -65,12 +65,8 @@ HOST_GCC_FINAL_CONF_OPTS = \
HOST_GCC_FINAL_GCC_LIB_DIR = $(HOST_DIR)/usr/$(GNU_TARGET_NAME)/lib*
# The kernel wants to use the -m4-nofpu option to make sure that it
# doesn't use floating point operations.
-ifeq ($(BR2_sh4)$(BR2_sh4eb),y)
-HOST_GCC_FINAL_CONF_OPTS += "--with-multilib-list=m4,m4-nofpu"
-HOST_GCC_FINAL_GCC_LIB_DIR = $(HOST_DIR)/usr/$(GNU_TARGET_NAME)/lib/!m4*
-endif
-ifeq ($(BR2_sh4a)$(BR2_sh4aeb),y)
-HOST_GCC_FINAL_CONF_OPTS += "--with-multilib-list=m4a,m4a-nofpu"
+ifeq ($(BR2_sh4)$(BR2_sh4eb)$(BR2_sh4a)$(BR2_sh4aeb),y)
+HOST_GCC_FINAL_CONF_OPTS += "--with-multilib-list=m4,m4-nofpu,m4a,m4a-nofpu"
HOST_GCC_FINAL_GCC_LIB_DIR = $(HOST_DIR)/usr/$(GNU_TARGET_NAME)/lib/!m4*
endif
Could you try this patch and see if it works?
Thanks!
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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