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Message-ID: <1529544276-28103-1-git-send-email-alankao@andestech.com>
Date: Thu, 21 Jun 2018 09:24:36 +0800
From: Alan Kao <alankao@...estech.com>
To: Palmer Dabbelt <palmer@...ive.com>, Albert Ou <albert@...ive.com>,
<linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC: Alan Kao <alankao@...estech.com>,
Greentime Hu <greentime@...estech.com>,
Zong Li <zong@...estech.com>
Subject: [PATCH] riscv: Add support to no-FPU systems
This patch adds an option, CONFIG_FPU, so that we can enable/disable
floating procedures in kernel.
Signed-off-by: Alan Kao <alankao@...estech.com>
Cc: Greentime Hu <greentime@...estech.com>
Cc: Zong Li <zong@...estech.com>
---
arch/riscv/Kconfig | 4 ++++
arch/riscv/Makefile | 4 ++++
arch/riscv/include/asm/switch_to.h | 4 ++++
arch/riscv/kernel/entry.S | 3 ++-
arch/riscv/kernel/process.c | 6 ++++++
arch/riscv/kernel/signal.c | 6 ++++++
6 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 6debcc4afc72..429d0bf777c9 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -232,6 +232,10 @@ config RISCV_BASE_PMU
endmenu
+config FPU
+ bool "FPU support"
+ default y
+
endmenu
menu "Kernel type"
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 76e958a5414a..2719e768c4dc 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -47,7 +47,11 @@ ifeq ($(CONFIG_RISCV_ISA_C),y)
KBUILD_ARCH_C = c
endif
+ifeq ($(CONFIG_FPU),y)
KBUILD_AFLAGS += -march=$(KBUILD_MARCH)$(KBUILD_ARCH_A)fd$(KBUILD_ARCH_C)
+else
+KBUILD_AFLAGS += -march=$(KBUILD_MARCH)$(KBUILD_ARCH_A)$(KBUILD_ARCH_C)
+endif
KBUILD_CFLAGS += -march=$(KBUILD_MARCH)$(KBUILD_ARCH_A)$(KBUILD_ARCH_C)
KBUILD_CFLAGS += -mno-save-restore
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index dd6b05bff75b..da0327a74466 100644
--- 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);
@@ -54,6 +55,9 @@ static inline void __switch_to_aux(struct task_struct *prev,
fstate_save(prev, regs);
fstate_restore(next, task_pt_regs(next));
}
+#else
+#define __switch_to_aux(__prev, __next)
+#endif
extern struct task_struct *__switch_to(struct task_struct *,
struct task_struct *);
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 9aaf6c986771..89867c9aa4f5 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -357,6 +357,7 @@ ENTRY(__switch_to)
ret
ENDPROC(__switch_to)
+#ifdef CONFIG_FPU
ENTRY(__fstate_save)
li a2, TASK_THREAD_F0
add a0, a0, a2
@@ -442,7 +443,7 @@ ENTRY(__fstate_restore)
csrc sstatus, t1
ret
ENDPROC(__fstate_restore)
-
+#endif
.section ".rodata"
/* Exception vector table */
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index cb209139ba53..a817046e478a 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -83,7 +83,11 @@ void show_regs(struct pt_regs *regs)
void start_thread(struct pt_regs *regs, unsigned long pc,
unsigned long sp)
{
+#ifdef CONFIG_FPU
regs->sstatus = SR_SPIE /* User mode, irqs on */ | SR_FS_INITIAL;
+#else
+ regs->sstatus = SR_SPIE | SR_FS_OFF;
+#endif
regs->sepc = pc;
regs->sp = sp;
set_fs(USER_DS);
@@ -101,7 +105,9 @@ void flush_thread(void)
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
+#ifdef CONFIG_FPU
fstate_save(src, task_pt_regs(src));
+#endif
*dst = *src;
return 0;
}
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 718d0c984ef0..0f659c9ef465 100644
--- 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_d_state(struct pt_regs *regs,
struct __riscv_d_ext_state __user *state)
{
@@ -53,6 +54,7 @@ static long save_d_state(struct pt_regs *regs,
fstate_save(current, regs);
return __copy_to_user(state, ¤t->thread.fstate, sizeof(*state));
}
+#endif
static long restore_sigcontext(struct pt_regs *regs,
struct sigcontext __user *sc)
@@ -63,6 +65,7 @@ static long restore_sigcontext(struct pt_regs *regs,
err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
if (unlikely(err))
return err;
+#ifdef CONFIG_FPU
/* Restore the floating-point state. */
err = restore_d_state(regs, &sc->sc_fpregs.d);
if (unlikely(err))
@@ -76,6 +79,7 @@ static long restore_sigcontext(struct pt_regs *regs,
if (value != 0)
return -EINVAL;
}
+#endif
return err;
}
@@ -127,11 +131,13 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
size_t i;
/* sc_regs is structured the same as the start of pt_regs */
err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
+#ifdef CONFIG_FPU
/* Save the floating-point state. */
err |= save_d_state(regs, &sc->sc_fpregs.d);
/* We support no other extension state at this time. */
for (i = 0; i < ARRAY_SIZE(sc->sc_fpregs.q.reserved); i++)
err |= __put_user(0, &sc->sc_fpregs.q.reserved[i]);
+#endif
return err;
}
--
2.17.0
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