Allow to disable FPU support

FPU codes have been separated from common part in previous patches.
This patch add the CONFIG_FPU option and some stubs, so that a no-FPU
configuration is allowed.

Signed-off-by: Alan Kao <alankao@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Vincent Chen <vincentc@andestech.com>
Cc: Zong Li <zong@andestech.com>
Cc: Nick Hu <nickhu@andestech.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a344980..a63f9db 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -208,6 +208,15 @@ config RISCV_BASE_PMU
 
 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"

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 01393e1..901770f 100644 (file)
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -44,7 +44,7 @@ KBUILD_CFLAGS += -Wall
 riscv-march-$(CONFIG_ARCH_RV32I)       := rv32im
 riscv-march-$(CONFIG_ARCH_RV64I)       := rv64im
 riscv-march-$(CONFIG_RISCV_ISA_A)      := $(riscv-march-y)a
-riscv-march-y                          := $(riscv-march-y)fd
+riscv-march-$(CONFIG_FPU)              := $(riscv-march-y)fd
 riscv-march-$(CONFIG_RISCV_ISA_C)      := $(riscv-march-y)c
 KBUILD_CFLAGS += -march=$(subst fd,,$(riscv-march-y))
 KBUILD_AFLAGS += -march=$(riscv-march-y)

diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index dd6b05b..093050b 100644 (file)
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -18,6 +18,7 @@
 #include <asm/ptrace.h>
 #include <asm/csr.h>
 
+#ifdef CONFIG_FPU
 extern void __fstate_save(struct task_struct *save_to);
 extern void __fstate_restore(struct task_struct *restore_from);
 
@@ -55,6 +56,15 @@ static inline void __switch_to_aux(struct task_struct *prev,
        fstate_restore(next, task_pt_regs(next));
 }
 
+#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_INITIAL)
+
+#else
+#define fstate_save(task, regs) do { } while (0)
+#define fstate_restore(task, regs) do { } while (0)
+#define __switch_to_aux(__prev, __next) do { } while (0)
+#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_OFF)
+#endif
+
 extern struct task_struct *__switch_to(struct task_struct *,
                                       struct task_struct *);
 

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index bd433ef..f13f7f2 100644 (file)
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -13,7 +13,6 @@ extra-y += vmlinux.lds
 obj-y  += cpu.o
 obj-y  += cpufeature.o
 obj-y  += entry.o
-obj-y  += fpu.o
 obj-y  += irq.o
 obj-y  += process.o
 obj-y  += ptrace.o
@@ -32,6 +31,7 @@ obj-y += vdso/
 
 CFLAGS_setup.o := -mcmodel=medany
 
+obj-$(CONFIG_FPU)              += fpu.o
 obj-$(CONFIG_SMP)              += smpboot.o
 obj-$(CONFIG_SMP)              += smp.o
 obj-$(CONFIG_MODULES)          += module.o

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index d7c6ca7..07d5156 100644 (file)
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -76,7 +76,7 @@ void show_regs(struct pt_regs *regs)
 void start_thread(struct pt_regs *regs, unsigned long pc,
        unsigned long sp)
 {
-       regs->sstatus = SR_SPIE /* User mode, irqs on */ | SR_FS_INITIAL;
+       regs->sstatus = DEFAULT_SSTATUS;
        regs->sepc = pc;
        regs->sp = sp;
        set_fs(USER_DS);
@@ -84,12 +84,14 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
 
 void flush_thread(void)
 {
+#ifdef CONFIG_FPU
        /*
         * Reset FPU context
         *      frm: round to nearest, ties to even (IEEE default)
         *      fflags: accrued exceptions cleared
         */
        memset(&current->thread.fstate, 0, sizeof(current->thread.fstate));
+#endif
 }
 
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)

diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 6a18b98..2450b82 100644 (file)
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -37,6 +37,7 @@ struct rt_sigframe {
        struct ucontext uc;
 };
 
+#ifdef CONFIG_FPU
 static long restore_fp_state(struct pt_regs *regs,
                             union __riscv_fp_state *sc_fpregs)
 {
@@ -85,6 +86,10 @@ static long save_fp_state(struct pt_regs *regs,
 
        return err;
 }
+#else
+#define save_fp_state(task, regs) (0)
+#define restore_fp_state(task, regs) (0)
+#endif
 
 static long restore_sigcontext(struct pt_regs *regs,
        struct sigcontext __user *sc)