board/zinger: fix compiler error when building with clang

When compiling with clang, it reports the following error:

board/zinger/runtime.c:271:2: error: non-ASM statement in naked function is not
supported
        cpu_reset();
        ^
board/zinger/runtime.c:258:43: note: attribute is here
void exception_panic(void) __attribute__((naked));

This is a partial revert of commit
28c034e69e6610602ef592b89476ce48e7ce58e8. Instead of replacing the "b
cpu_reset" with a C call to cpu_reset(), change to "bl cpu_reset", which
is the same thing.

The code generated by gcc for exception_panic is the same before and
after this change:

00000000 <exception_panic>:
   0:   4b04            ldr     r3, [pc, #16]   ; (14 <exception_panic+0x14>)
   2:   1c18            adds    r0, r3, #0
   4:   466b            mov     r3, sp
   6:   6999            ldr     r1, [r3, #24]
   8:   695a            ldr     r2, [r3, #20]
   a:   f7ff fffe       bl      0 <debug_printf>
   e:   f7ff fffe       bl      0 <exception_panic>
  12:   46c0            nop                     ; (mov r8, r8)
  14:   00000000        .word   0x00000000

BRANCH=none
BUG=b:172020503, b:172343310
TEST=make CC=arm-none-eabi-clang BOARD=zinger -j
TEST=make buildall -j

Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: I590ba4d2caabc77f04288d9f566286e87d08df02
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3198205
Reviewed-by: Eric Yilun Lin <yllin@google.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/board/zinger/runtime.c b/board/zinger/runtime.c
index 5d17bfda04..cb27cc0f03 100644
--- a/board/zinger/runtime.c
+++ b/board/zinger/runtime.c
@@ -258,17 +258,17 @@ void system_reset(int flags)
 void exception_panic(void) __attribute__((naked));
 void exception_panic(void)
 {
-#ifdef CONFIG_DEBUG_PRINTF
 	asm volatile(
+#ifdef CONFIG_DEBUG_PRINTF
 		"mov r0, %0\n"
 		/* TODO: Should this be SP_process instead of SP_main? */
 		"mov r3, sp\n"
 		"ldr r1, [r3, #6*4]\n" /* retrieve exception PC */
 		"ldr r2, [r3, #5*4]\n" /* retrieve exception LR */
 		"bl debug_printf\n"
-	: : "r"("PANIC PC=%08x LR=%08x\n\n"));
 #endif
-	cpu_reset();
+		"bl cpu_reset\n"
+	: : "r"("PANIC PC=%08x LR=%08x\n\n"));
 }
 
 void panic_reboot(void)