arch/xtensa: Clean up MMU initialization

We were trying to initialize the MMU extremely early (out of crt1.S),
which was forcing some odd gymnastics with splitting up the
initialization paths.  Just don't do that.

The MMU boots with a pefectly good mapping for physical memory.  Use
that until we're set up and about to launch the post-arch
initialization in z_cstart().

Just in general, trying to run compiled C code before z_cstart() calls
kernel_arch_init() is asking for trouble.  We do it only in extreme
situations, and we don't need it here.

Signed-off-by: Andy Ross <andyross@google.com>

Author: andyross

arch/xtensa/core/crt1.S

@@ -25,11 +25,6 @@
 .type	z_cstart, @function
 .type	z_mp_entry, @function
 
-#ifdef CONFIG_XTENSA_MMU
-.type	z_xtensa_mmu_init, @function
-#endif
-
-
 /* Macros to abstract away ABI differences */
 
 #if __XTENSA_CALL0_ABI__
@@ -193,10 +188,6 @@ _start:
 
 #endif /* !XCHAL_HAVE_BOOTLOADER */
 
-#ifdef CONFIG_XTENSA_MMU
-	CALL	z_xtensa_mmu_init
-#endif
-
 	/* Enter C domain, never returns from here */
 	CALL	z_cstart
 

arch/xtensa/core/ptables.c

@@ -215,24 +215,12 @@ static inline void xtensa_init_page_tables(void)
 			 PAGE_TABLE_ATTR | Z_XTENSA_MMU_W);
 }
 
-/* Called out of pre-z_cstart init code on CPU 0 */
+/* Called out of arch_kernel_init() just after entry to z_cstart() */
 void z_xtensa_mmu_init(void)
 {
-	/* This is normally done via arch_kernel_init() inside z_cstart().
-	 * However, before that is called, we go through the sys_init of
-	 * INIT_LEVEL_EARLY, which is going to result in TLB misses.
-	 * So setup whatever necessary so the exception handler can work
-	 * properly.
-	 */
-	z_xtensa_kernel_init();
-
-	xtensa_init_page_tables();
-	xtensa_init_paging(l1_page_table);
-}
-
-/* Called out of early init code on CPU 1+ */
-void z_xtensa_mmu_smp_init(void)
-{
+	if (_current_cpu->id == 0) {
+		xtensa_init_page_tables();
+	}
 	xtensa_init_paging(l1_page_table);
 }
 

arch/xtensa/include/kernel_arch_func.h

@@ -25,7 +25,7 @@ extern void z_xtensa_fatal_error(unsigned int reason, const z_arch_esf_t *esf);
 K_KERNEL_STACK_ARRAY_DECLARE(z_interrupt_stacks, CONFIG_MP_MAX_NUM_CPUS,
 			     CONFIG_ISR_STACK_SIZE);
 
-static ALWAYS_INLINE void z_xtensa_kernel_init(void)
+static ALWAYS_INLINE void arch_kernel_init(void)
 {
 	_cpu_t *cpu0 = &_kernel.cpus[0];
 
@@ -51,21 +51,15 @@ static ALWAYS_INLINE void z_xtensa_kernel_init(void)
 	 * win.
 	 */
 	XTENSA_WSR(ZSR_CPU_STR, cpu0);
-}
-
-static ALWAYS_INLINE void arch_kernel_init(void)
-{
-#ifndef CONFIG_XTENSA_MMU
-	/* This is called in z_xtensa_mmu_init() before z_cstart()
-	 * so we do not need to call it again.
-	 */
-	z_xtensa_kernel_init();
-#endif
 
 #ifdef CONFIG_INIT_STACKS
 	memset(Z_KERNEL_STACK_BUFFER(z_interrupt_stacks[0]), 0xAA,
 	       K_KERNEL_STACK_SIZEOF(z_interrupt_stacks[0]));
 #endif
+
+#ifdef CONFIG_XTENSA_MMU
+	z_xtensa_mmu_init();
+#endif
 }
 
 void xtensa_switch(void *switch_to, void **switched_from);