From: Palmer Dabbelt <palmer@sifive.com>
Date: Tue, 23 Oct 2018 00:38:26 +0000 (-0700)
Subject: riscv: Add support to no-FPU systems
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4e4101cfefd382176b05356c5ef112561ae10384;p=linux.git

riscv: Add support to no-FPU systems

This patchset adds an option, CONFIG_FPU, to enable/disable floating-
point support within the kernel.  The kernel's new behavior will be as
follows:

* with CONFIG_FPU=y
  All FPU codes are reserved.  If no FPU is found during booting, a
  global flag will be set, and those functions will be bypassed with
  condition check to that flag.

* with CONFIG_FPU=n
  No floating-point instructions in kernel and all related settings
  are excluded.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
---

4e4101cfefd382176b05356c5ef112561ae10384
diff --cc arch/riscv/Kconfig
index 6c8329beb9368,a63f9dbb47060..4198759f67987
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@@ -210,9 -208,18 +210,18 @@@ config RISCV_BASE_PM
  
  endmenu
  
+ config FPU
+ 	bool "FPU support"
+ 	default y
+ 	help
+ 	  Say N here if you want to disable all floating-point related procedure
+ 	  in the kernel.
+ 
+ 	  If you don't know what to do here, say Y.
+ 
  endmenu
  
 -menu "Kernel type"
 +menu "Kernel features"
  
  source "kernel/Kconfig.hz"
  
diff --cc arch/riscv/Makefile
index 33700e4bfc3bc,901770fc9bd2c..d10146197533a
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@@ -25,8 -25,9 +25,7 @@@ ifeq ($(CONFIG_ARCH_RV64I),y
  
  	KBUILD_CFLAGS += -mabi=lp64
  	KBUILD_AFLAGS += -mabi=lp64
 -	
 -	KBUILD_CFLAGS	+= $(call cc-ifversion, -ge, 0500, -DCONFIG_ARCH_SUPPORTS_INT128)
  
- 	KBUILD_MARCH = rv64im
  	KBUILD_LDFLAGS += -melf64lriscv
  else
  	BITS := 32
diff --cc arch/riscv/kernel/cpufeature.c
index 652d102ffa06d,46942e6352668..5493f32287047
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@@ -57,12 -60,10 +60,17 @@@ void riscv_fill_hwcap(void
  	for (i = 0; i < strlen(isa); ++i)
  		elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
  
 +	/* We don't support systems with F but without D, so mask those out
 +	 * here. */
 +	if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
 +		pr_info("This kernel does not support systems with F but not D");
 +		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
 +	}
 +
  	pr_info("elf_hwcap is 0x%lx", elf_hwcap);
+ 
+ #ifdef CONFIG_FPU
+ 	if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
+ 		has_fpu = true;
+ #endif
  }