riscv: support building double-float modules

The riscv32 toolchain for GCC-12 provided by kernel.org contains libgcc.a
compiled for double-float. To link to it we have to adjust how we build
U-Boot.

As U-Boot actually does not use floating point at all this should not
make a significant difference for the produced binaries.

Signed-off-by: Heinrich Schuchardt <[email protected]>
Reviewed-by: Rick Chen <[email protected]>
Reviewed-by: Leo Yu-Chi Liang <[email protected]>

arch/riscv/Kconfig

@@ -152,6 +152,21 @@ config RISCV_ISA_C
 	  when building U-Boot, which results in compressed instructions in the
 	  U-Boot binary.
 
+config RISCV_ISA_F
+	bool "Standard extension for Single-Precision Floating Point"
+	default y
+	help
+	  Adds "F" to the ISA string passed to the compiler.
+
+config RISCV_ISA_D
+	bool "Standard extension for Double-Precision Floating Point"
+	depends on RISCV_ISA_F
+	default y
+	help
+	  Adds "D" to the ISA string passed to the compiler and changes the
+	  riscv32 ABI from ilp32 to ilp32d and the riscv64 ABI from lp64 to
+	  lp64d.
+
 config RISCV_ISA_A
 	def_bool y
 

arch/riscv/Makefile

@@ -5,15 +5,22 @@
 
 ifeq ($(CONFIG_ARCH_RV64I),y)
 	ARCH_BASE = rv64im
-	ABI = lp64
+	ABI_BASE = lp64
 endif
 ifeq ($(CONFIG_ARCH_RV32I),y)
 	ARCH_BASE = rv32im
-	ABI = ilp32
+	ABI_BASE = ilp32
 endif
 ifeq ($(CONFIG_RISCV_ISA_A),y)
 	ARCH_A = a
 endif
+ifeq ($(CONFIG_RISCV_ISA_F),y)
+	ARCH_F = f
+endif
+ifeq ($(CONFIG_RISCV_ISA_D),y)
+	ARCH_D = d
+	ABI_D = d
+endif
 ifeq ($(CONFIG_RISCV_ISA_C),y)
 	ARCH_C = c
 endif
@@ -24,7 +31,9 @@ ifeq ($(CONFIG_CMODEL_MEDANY),y)
 	CMODEL = medany
 endif
 
-RISCV_MARCH = $(ARCH_BASE)$(ARCH_A)$(ARCH_C)
+
+RISCV_MARCH = $(ARCH_BASE)$(ARCH_A)$(ARCH_F)$(ARCH_D)$(ARCH_C)
+ABI = $(ABI_BASE)$(ABI_D)
 
 # Newer binutils versions default to ISA spec version 20191213 which moves some
 # instructions from the I extension to the Zicsr and Zifencei extensions.