[PATCH 2/3] powerpc/83xx: Fix build failure with FPU=n

[Michael Ellerman]

Building eg. 83xx/mpc832x_rdb_defconfig with FPU=n, fails with:

  arch/powerpc/platforms/83xx/suspend.c: In function 'mpc83xx_suspend_enter':
  arch/powerpc/platforms/83xx/suspend.c:209:17: error: implicit declaration of function 'enable_kernel_fp'
    209 |                 enable_kernel_fp();

Fix it by providing an enable_kernel_fp() stub for FPU=n builds,
which allows using IS_ENABLED(CONFIG_PPC_FPU) around the call to
enable_kernel_fp().

Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
---
 arch/powerpc/include/asm/switch_to.h  | 4 ++++
 arch/powerpc/platforms/83xx/suspend.c | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index aee25e3ebf96..fc933807ddc8 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -48,6 +48,10 @@ static inline void disable_kernel_fp(void)
 #else
 static inline void save_fpu(struct task_struct *t) { }
 static inline void flush_fp_to_thread(struct task_struct *t) { }
+static inline void enable_kernel_fp(void)
+{
+	BUILD_BUG();
+}
 #endif
 
 #ifdef CONFIG_ALTIVEC
diff --git a/arch/powerpc/platforms/83xx/suspend.c b/arch/powerpc/platforms/83xx/suspend.c
index c9664e46b03d..99bd4355f28e 100644
--- a/arch/powerpc/platforms/83xx/suspend.c
+++ b/arch/powerpc/platforms/83xx/suspend.c
@@ -206,7 +206,8 @@ static int mpc83xx_suspend_enter(suspend_state_t state)
 		out_be32(&pmc_regs->config1,
 		         in_be32(&pmc_regs->config1) | PMCCR1_POWER_OFF);
 
-		enable_kernel_fp();
+		if (IS_ENABLED(CONFIG_PPC_FPU))
+			enable_kernel_fp();
 
 		mpc83xx_enter_deep_sleep(immrbase);
 
-- 
2.43.2