linux_dsm_epyc7002/arch/mips/loongson64/Platform
Paul Burton 2f2b4fd674
MIPS: Disable Loongson MMI instructions for kernel build
GCC 9.x automatically enables support for Loongson MMI instructions when
using some -march= flags, and then errors out when -msoft-float is
specified with:

  cc1: error: ‘-mloongson-mmi’ must be used with ‘-mhard-float’

The kernel shouldn't be using these MMI instructions anyway, just as it
doesn't use floating point instructions. Explicitly disable them in
order to fix the build with GCC 9.x.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 3702bba5eb ("MIPS: Loongson: Add GCC 4.4 support for Loongson2E")
Fixes: 6f7a251a25 ("MIPS: Loongson: Add basic Loongson 2F support")
Fixes: 5188129b8c ("MIPS: Loongson-3: Improve -march option and move it to Platform")
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: stable@vger.kernel.org # v2.6.32+
Cc: linux-mips@vger.kernel.org
2019-10-10 11:58:52 -07:00

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#
# Loongson Processors' Support
#
# Only gcc >= 4.4 have Loongson specific support
cflags-$(CONFIG_CPU_LOONGSON2) += -Wa,--trap
cflags-$(CONFIG_CPU_LOONGSON2E) += \
$(call cc-option,-march=loongson2e,-march=r4600)
cflags-$(CONFIG_CPU_LOONGSON2F) += \
$(call cc-option,-march=loongson2f,-march=r4600)
# Enable the workarounds for Loongson2f
ifdef CONFIG_CPU_LOONGSON2F_WORKAROUNDS
ifeq ($(call as-option,-Wa$(comma)-mfix-loongson2f-nop,),)
$(error only binutils >= 2.20.2 have needed option -mfix-loongson2f-nop)
else
cflags-$(CONFIG_CPU_NOP_WORKAROUNDS) += -Wa$(comma)-mfix-loongson2f-nop
endif
ifeq ($(call as-option,-Wa$(comma)-mfix-loongson2f-jump,),)
$(error only binutils >= 2.20.2 have needed option -mfix-loongson2f-jump)
else
cflags-$(CONFIG_CPU_JUMP_WORKAROUNDS) += -Wa$(comma)-mfix-loongson2f-jump
endif
endif
cflags-$(CONFIG_CPU_LOONGSON3) += -Wa,--trap
#
# Some versions of binutils, not currently mainline as of 2019/02/04, support
# an -mfix-loongson3-llsc flag which emits a sync prior to each ll instruction
# to work around a CPU bug (see loongson_llsc_mb() in asm/barrier.h for a
# description).
#
# We disable this in order to prevent the assembler meddling with the
# instruction that labels refer to, ie. if we label an ll instruction:
#
# 1: ll v0, 0(a0)
#
# ...then with the assembler fix applied the label may actually point at a sync
# instruction inserted by the assembler, and if we were using the label in an
# exception table the table would no longer contain the address of the ll
# instruction.
#
# Avoid this by explicitly disabling that assembler behaviour. If upstream
# binutils does not merge support for the flag then we can revisit & remove
# this later - for now it ensures vendor toolchains don't cause problems.
#
cflags-$(CONFIG_CPU_LOONGSON3) += $(call as-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
#
# binutils from v2.25 on and gcc starting from v4.9.0 treat -march=loongson3a
# as MIPS64 R2; older versions as just R1. This leaves the possibility open
# that GCC might generate R2 code for -march=loongson3a which then is rejected
# by GAS. The cc-option can't probe for this behaviour so -march=loongson3a
# can't easily be used safely within the kbuild framework.
#
ifeq ($(call cc-ifversion, -ge, 0409, y), y)
ifeq ($(call ld-ifversion, -ge, 225000000, y), y)
cflags-$(CONFIG_CPU_LOONGSON3) += \
$(call cc-option,-march=loongson3a -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
else
cflags-$(CONFIG_CPU_LOONGSON3) += \
$(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
endif
else
cflags-$(CONFIG_CPU_LOONGSON3) += \
$(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
endif
# Some -march= flags enable MMI instructions, and GCC complains about that
# support being enabled alongside -msoft-float. Thus explicitly disable MMI.
cflags-y += $(call cc-option,-mno-loongson-mmi)
#
# Loongson Machines' Support
#
platform-$(CONFIG_MACH_LOONGSON64) += loongson64/
cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 -mno-branch-likely
load-$(CONFIG_LEMOTE_FULOONG2E) += 0xffffffff80100000
load-$(CONFIG_LEMOTE_MACH2F) += 0xffffffff80200000
load-$(CONFIG_LOONGSON_MACH3X) += 0xffffffff80200000