arm64: tegra132: tegra210: Remove old arm64/stage_entry.S

This patch removes the old arm64/stage_entry.S code that was too
specific to the Tegra SoC boot flow, and replaces it with code that
hides the peculiarities of switching to a different CPU/arch in ramstage
in the Tegra SoC directories.

BRANCH=None
BUG=None
TEST=Built Ryu and Smaug. !!!UNTESTED!!!

Change-Id: Ib3a0448b30ac9c7132581464573efd5e86e03698
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/12078
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

33 files changed, 126 insertions, 440 deletions

diff --git a/src/arch/arm64/Kconfig b/src/arch/arm64/Kconfig
index 9b06589f82..21bbc9b939 100644
--- a/src/arch/arm64/Kconfig
+++ b/src/arch/arm64/Kconfig
@@ -20,7 +20,6 @@ config ARCH_RAMSTAGE_ARM64
 	default n
 
 source src/arch/arm64/armv8/Kconfig
-source src/arch/arm64/cpu/Kconfig
 
 config ARM64_USE_ARM_TRUSTED_FIRMWARE
 	bool
diff --git a/src/arch/arm64/Makefile.inc b/src/arch/arm64/Makefile.inc
index 21fda04bda..1cbc9a407d 100644
--- a/src/arch/arm64/Makefile.inc
+++ b/src/arch/arm64/Makefile.inc
@@ -23,7 +23,7 @@
 # Take care of subdirectories
 ################################################################################
 
-subdirs-y += armv8/ cpu/
+subdirs-y += armv8/
 
 ################################################################################
 # ARM specific options
@@ -44,8 +44,6 @@ bootblock-y += id.S
 $(obj)/arch/arm64/id.bootblock.o: $(obj)/build.h
 
 bootblock-y += boot.c
-bootblock-y += c_entry.c
-bootblock-y += cpu-stubs.c
 bootblock-y += eabi_compat.c
 bootblock-y += transition.c transition_asm.S
 
@@ -87,8 +85,6 @@ endif # CONFIG_ARCH_VERSTAGE_ARM64
 ifeq ($(CONFIG_ARCH_ROMSTAGE_ARM64),y)
 
 romstage-y += boot.c
-romstage-y += c_entry.c
-romstage-y += cpu-stubs.c
 romstage-y += div0.c
 romstage-y += eabi_compat.c
 romstage-y += memset.S
@@ -113,7 +109,6 @@ endif # CONFIG_ARCH_ROMSTAGE_ARM64
 
 ifeq ($(CONFIG_ARCH_RAMSTAGE_ARM64),y)
 
-ramstage-y += c_entry.c
 ramstage-y += div0.c
 ramstage-y += eabi_compat.c
 ramstage-y += boot.c
@@ -121,15 +116,9 @@ ramstage-y += tables.c
 ramstage-y += memset.S
 ramstage-y += memcpy.S
 ramstage-y += memmove.S
-ramstage-y += cpu-stubs.c
 ramstage-$(CONFIG_ARM64_USE_ARM_TRUSTED_FIRMWARE) += arm_tf.c
 ramstage-y += transition.c transition_asm.S
 
-# TODO: Replace this with a simpler ramstage entry point in soc/nvidia/tegra*
-ifeq ($(CONFIG_SOC_NVIDIA_TEGRA132)$(CONFIG_SOC_NVIDIA_TEGRA210),y)
-ramstage-y += stage_entry.S
-endif
-
 rmodules_arm64-y += memset.S
 rmodules_arm64-y += memcpy.S
 rmodules_arm64-y += memmove.S
diff --git a/src/arch/arm64/armv8/bootblock.S b/src/arch/arm64/armv8/bootblock.S
index 4a9fea9af6..e5758bca0d 100644
--- a/src/arch/arm64/armv8/bootblock.S
+++ b/src/arch/arm64/armv8/bootblock.S
@@ -16,21 +16,14 @@
 
 #include <arch/asm.h>
 
+/* NOTE: When making changes to general ARM64 initialization, keep in mind that
+ * there are other CPU entry points, using BOOTBLOCK_CUSTOM or entering the CPU
+ * in a later stage (like Tegra). Changes should generally be put into
+ * arm64_cpu_init so they can be shared between those instances. */
+
 ENTRY(_start)
-	/* Initialize PSTATE, SCTLR and caches to clean state. */
+	/* Initialize PSTATE, SCTLR and caches to clean state, set up stack. */
 	bl	arm64_init_cpu
 
-	/* Initialize stack with sentinel value to later check overflow. */
-	ldr	x0, =_stack
-	ldr	x1, =_estack
-	ldr	x2, =0xdeadbeefdeadbeef
-stack_init_loop:
-	stp	x2, x2, [x0], #16
-	cmp	x0, x1
-	bne	stack_init_loop
-
-	/* Leave a line of beef dead for easier visibility in stack dumps. */
-	sub	sp, x0, #16
-
 	bl	main
 ENDPROC(_start)
diff --git a/src/arch/arm64/armv8/cpu.S b/src/arch/arm64/armv8/cpu.S
index 4713ca59f9..711c338685 100644
--- a/src/arch/arm64/armv8/cpu.S
+++ b/src/arch/arm64/armv8/cpu.S
@@ -21,7 +21,8 @@
  * Bring an ARMv8 processor we just gained control of (e.g. from IROM) into a
  * known state regarding caches/SCTLR/PSTATE. Completely cleans and invalidates
  * icache/dcache, disables MMU and dcache (if active), and enables unaligned
- * accesses, icache and branch prediction (if inactive). Clobbers R22 and R23.
+ * accesses, icache and branch prediction (if inactive). Seeds the stack and
+ * initializes SP_EL0. Clobbers R22 and R23.
  */
 ENTRY(arm64_init_cpu)
 	/* Initialize PSTATE (unmask all exceptions, select SP_EL0). */
@@ -60,5 +61,17 @@ ENTRY(arm64_init_cpu)
 	dsb	sy
 	isb
 
+	/* Initialize stack with sentinel value to later check overflow. */
+	ldr	x2, =0xdeadbeefdeadbeef
+	ldr	x0, =_stack
+	ldr	x1, =_estack
+1:
+	stp	x2, x2, [x0], #16
+	cmp	x0, x1
+	bne	1b
+
+	/* Leave a line of beef dead for easier visibility in stack dumps. */
+	sub	sp, x0, #16
+
 	ret	x23
 ENDPROC(arm64_init_cpu)
diff --git a/src/arch/arm64/armv8/exception.c b/src/arch/arm64/armv8/exception.c
index 35e3f7fac6..b872a55a8a 100644
--- a/src/arch/arm64/armv8/exception.c
+++ b/src/arch/arm64/armv8/exception.c
@@ -166,7 +166,6 @@ void exc_dispatch(struct exc_state *state, uint64_t idx)
 	exc_exit(&state->regs);
 }
 
-
 static int test_exception_handler(struct exc_state *state, uint64_t vector_id)
 {
 	/* Update instruction pointer to next instrution. */
diff --git a/src/arch/arm64/boot.c b/src/arch/arm64/boot.c
index 1012d97a0a..c996d503f5 100644
--- a/src/arch/arm64/boot.c
+++ b/src/arch/arm64/boot.c
@@ -72,10 +72,8 @@ void arch_prog_run(struct prog *prog)
 	doit(prog_entry_arg(prog));
 }
 
-#if !IS_ENABLED(CONFIG_SOC_NVIDIA_TEGRA132)
 /* Generic stage entry point. Can be overridden by board/SoC if needed. */
 __attribute__((weak)) void stage_entry(void)
 {
 	main();
 }
-#endif
diff --git a/src/arch/arm64/c_entry.c b/src/arch/arm64/c_entry.c
deleted file mode 100644
index f26ed926b1..0000000000
--- a/src/arch/arm64/c_entry.c
+++ /dev/null
@@ -1,128 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright 2014 Google Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- */
-
-#include <arch/cache.h>
-#include <arch/cpu.h>
-#include <arch/lib_helpers.h>
-#include <arch/mmu.h>
-#include <arch/stages.h>
-#include <gic.h>
-
-#include "cpu-internal.h"
-
-void __attribute__((weak)) arm64_soc_init(void)
-{
-	/* Default weak implementation does nothing. */
-}
-
-static void seed_stack(void)
-{
-	char *stack_begin;
-	uint64_t *slot;
-	int i;
-	int size;
-
-	stack_begin = cpu_get_stack();
-	stack_begin -= CONFIG_STACK_SIZE;
-	slot = (void *)stack_begin;
-
-	/* Pad out 256 bytes for current usage. */
-	size = CONFIG_STACK_SIZE - 256;
-	size /= sizeof(*slot);
-	for (i = 0; i < size; i++)
-		*slot++ = 0xdeadbeefdeadbeefULL;
-}
-
-/* Set up default SCR values. */
-static void el3_init(void)
-{
-	uint32_t scr;
-
-	if (get_current_el() != EL3)
-		return;
-
-	scr = raw_read_scr_el3();
-	/* Default to non-secure EL1 and EL0. */
-	scr &= ~(SCR_NS_MASK);
-	scr |= SCR_NS_ENABLE;
-	/* Disable IRQ, FIQ, and external abort interrupt routing. */
-	scr &= ~(SCR_IRQ_MASK | SCR_FIQ_MASK | SCR_EA_MASK);
-	scr |= SCR_IRQ_DISABLE | SCR_FIQ_DISABLE | SCR_EA_DISABLE;
-	/* Enable HVC */
-	scr &= ~(SCR_HVC_MASK);
-	scr |= SCR_HVC_ENABLE;
-	/* Disable SMC */
-	scr &= ~(SCR_SMC_MASK);
-	scr |= SCR_SMC_DISABLE;
-	/* Disable secure instruction fetches. */
-	scr &= ~(SCR_SIF_MASK);
-	scr |= SCR_SIF_DISABLE;
-	/* All lower exception levels 64-bit by default. */
-	scr &= ~(SCR_RW_MASK);
-	scr |= SCR_LOWER_AARCH64;
-	/* Disable secure EL1 access to secure timer. */
-	scr &= ~(SCR_ST_MASK);
-	scr |= SCR_ST_DISABLE;
-	/* Don't trap on WFE or WFI instructions. */
-	scr &= ~(SCR_TWI_MASK | SCR_TWE_MASK);
-	scr |= SCR_TWI_DISABLE | SCR_TWE_DISABLE;
-	raw_write_scr_el3(scr);
-	isb();
-}
-
-void __attribute__((weak)) arm64_arch_timer_init(void)
-{
-	/* Default weak implementation does nothing. */
-}
-
-static void arm64_init(void)
-{
-	seed_stack();
-
-	/* Set up default SCR values. */
-	el3_init();
-
-	/* Initialize the GIC. */
-	gic_init();
-
-	/*
-	 * Disable coprocessor traps to EL3:
-	 * TCPAC [20] = 0, disable traps for EL2 accesses to CPTR_EL2 or HCPTR
-	 * and EL2/EL1 access to CPACR_EL1.
-	 * TTA [20] = 0, disable traps for trace register access from any EL.
-	 * TFP [10] = 0, disable traps for floating-point instructions from any
-	 * EL.
-	 */
-	raw_write_cptr_el3(CPTR_EL3_TCPAC_DISABLE | CPTR_EL3_TTA_DISABLE |
-			   CPTR_EL3_TFP_DISABLE);
-
-	/*
-	 * Allow FPU accesses:
-	 * FPEN [21:20] = 3, disable traps for floating-point instructions from
-	 * EL0/EL1.
-	 * TTA [28] = 0, disable traps for trace register access from EL0/EL1.
-	 */
-	raw_write_cpacr_el1(CPACR_TRAP_FP_DISABLE | CPACR_TTA_DISABLE);
-
-	/* Arch Timer init: setup cntfrq per CPU */
-	arm64_arch_timer_init();
-
-	arm64_soc_init();
-
-	main();
-}
-
-/* This variable holds entry point for CPU starting up. */
-void (*c_entry)(void) = &arm64_init;
diff --git a/src/arch/arm64/cpu-internal.h b/src/arch/arm64/cpu-internal.h
deleted file mode 100644
index 75d2d4deb6..0000000000
--- a/src/arch/arm64/cpu-internal.h
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright 2014 Google Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- */
-
-#ifndef ARCH_CPU_INTERNAL_H
-#define ARCH_CPU_INTERNAL_H
-
-/* Return the top of the stack for the cpu. */
-void *cpu_get_stack(void);
-
-/* Return the top of the exception stack for the cpu. */
-void *cpu_get_exception_stack(void);
-
-#endif /* ARCH_CPU_INTERNAL_H */
diff --git a/src/arch/arm64/cpu-stubs.c b/src/arch/arm64/cpu-stubs.c
deleted file mode 100644
index 1a61872986..0000000000
--- a/src/arch/arm64/cpu-stubs.c
+++ /dev/null
@@ -1,21 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright 2015 Google Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- */
-
-void arm64_cpu_early_setup(void);
-
-void __attribute__((weak)) arm64_cpu_early_setup(void)
-{
-	/* Default empty implementation */
-}
diff --git a/src/arch/arm64/cpu/Kconfig b/src/arch/arm64/cpu/Kconfig
deleted file mode 100644
index 21526e6409..0000000000
--- a/src/arch/arm64/cpu/Kconfig
+++ /dev/null
@@ -1,19 +0,0 @@
-##
-## This file is part of the coreboot project.
-##
-## Copyright (C) 2015 Google Inc
-##
-## This program is free software; you can redistribute it and/or modify
-## it under the terms of the GNU General Public License as published by
-## the Free Software Foundation; version 2 of the License.
-##
-## This program is distributed in the hope that it will be useful,
-## but WITHOUT ANY WARRANTY; without even the implied warranty of
-## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-## GNU General Public License for more details.
-##
-
-config ARCH_ARM64_CPU_CORTEX_A57
-	bool
-	default n
-	depends on ARCH_ARM64
diff --git a/src/arch/arm64/cpu/Makefile.inc b/src/arch/arm64/cpu/Makefile.inc
deleted file mode 100644
index 4b249c7218..0000000000
--- a/src/arch/arm64/cpu/Makefile.inc
+++ /dev/null
@@ -1,20 +0,0 @@
-################################################################################
-##
-## This file is part of the coreboot project.
-##
-## Copyright 2015 Google Inc.
-##
-## This program is free software; you can redistribute it and/or modify
-## it under the terms of the GNU General Public License as published by
-## the Free Software Foundation; version 2 of the License.
-##
-## This program is distributed in the hope that it will be useful,
-## but WITHOUT ANY WARRANTY; without even the implied warranty of
-## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-## GNU General Public License for more details.
-##
-################################################################################
-
-ifeq ($(CONFIG_ARCH_RAMSTAGE_ARM64),y)
-ramstage-$(CONFIG_ARCH_ARM64_CPU_CORTEX_A57) += cortex_a57.S
-endif
diff --git a/src/arch/arm64/include/arch/memlayout.h b/src/arch/arm64/include/arch/memlayout.h
index 6db67a9dee..0bd0835aa8 100644
--- a/src/arch/arm64/include/arch/memlayout.h
+++ b/src/arch/arm64/include/arch/memlayout.h
@@ -23,13 +23,8 @@
 	_ = ASSERT(size % 4K == 0, "TTB size must be divisible by 4K!");
 
 /* ARM64 stacks need 16-byte alignment. */
-#if !(IS_ENABLED(CONFIG_SOC_NVIDIA_TEGRA132) || \
-      IS_ENABLED(CONFIG_SOC_NVIDIA_TEGRA210))
 #define STACK(addr, size) \
 	REGION(stack, addr, size, 16) \
 	_ = ASSERT(size >= 2K, "stack should be >= 2K, see toolchain.inc");
-#else	/* Hack around old Tegra stage_entry.S implementation. TODO: remove */
-#define STACK(addr, size) REGION(preram_stack, addr, size, 16)
-#endif
 
 #endif /* __ARCH_MEMLAYOUT_H */
diff --git a/src/arch/arm64/include/arch/stages.h b/src/arch/arm64/include/arch/stages.h
index 0d6606f389..6dbf389001 100644
--- a/src/arch/arm64/include/arch/stages.h
+++ b/src/arch/arm64/include/arch/stages.h
@@ -24,9 +24,4 @@ void stage_entry(void);
 void stage_exit(void *);
 void jmp_to_elf_entry(void *entry, unsigned long buffer, unsigned long size);
 
-/* This function is called upon initial entry of each stage. It is called prior
- * to main(). That means all of the common infrastructure will most likely not
- * be available to be used (such as console). */
-void arm64_soc_init(void);
-
 #endif
diff --git a/src/arch/arm64/include/armv8/arch/cpu.h b/src/arch/arm64/include/armv8/arch/cpu.h
index fdc34e5086..6e096cc8e6 100644
--- a/src/arch/arm64/include/armv8/arch/cpu.h
+++ b/src/arch/arm64/include/armv8/arch/cpu.h
@@ -20,18 +20,6 @@
 
 static inline unsigned int smp_processor_id(void) { return 0; }
 
-/*
- * The arm64_cpu_startup() initializes CPU's exception stack and regular
- * stack as well initializing the C environment for the processor. Finally it
- * calls into c_entry.
- */
-void arm64_cpu_startup(void);
-
-/*
- * The arm64_arch_timer_init() initializes the CPU's cntfrq register of
- * ARM arch timer.
- */
-void arm64_arch_timer_init(void);
 
 #if !defined(__PRE_RAM__)
 struct cpu_driver { };
diff --git a/src/arch/arm64/include/armv8/arch/lib_helpers.h b/src/arch/arm64/include/armv8/arch/lib_helpers.h
index 6dd33b352f..51a754a8af 100644
--- a/src/arch/arm64/include/armv8/arch/lib_helpers.h
+++ b/src/arch/arm64/include/armv8/arch/lib_helpers.h
@@ -58,10 +58,10 @@
 #define SCR_EA_MASK          (1 << SCR_EA_SHIFT)
 #define SCR_EA_ENABLE        (1 << SCR_EA_SHIFT)
 #define SCR_EA_DISABLE       (0 << SCR_EA_SHIFT)
-#define SCR_SMC_SHIFT        7
-#define SCR_SMC_MASK         (1 << SCR_SMC_SHIFT)
-#define SCR_SMC_DISABLE      (1 << SCR_SMC_SHIFT)
-#define SCR_SMC_ENABLE       (0 << SCR_SMC_SHIFT)
+#define SCR_SMD_SHIFT        7
+#define SCR_SMD_MASK         (1 << SCR_SMD_SHIFT)
+#define SCR_SMD_DISABLE      (1 << SCR_SMD_SHIFT)
+#define SCR_SMD_ENABLE       (0 << SCR_SMD_SHIFT)
 #define SCR_HVC_SHIFT        8
 #define SCR_HVC_MASK         (1 << SCR_HVC_SHIFT)
 #define SCR_HVC_DISABLE      (0 << SCR_HVC_SHIFT)
diff --git a/src/arch/arm64/transition.c b/src/arch/arm64/transition.c
index 3900421e8c..9edc011420 100644
--- a/src/arch/arm64/transition.c
+++ b/src/arch/arm64/transition.c
@@ -13,8 +13,10 @@
  * GNU General Public License for more details.
  */
 
+#include <arch/cache.h>
 #include <arch/lib_helpers.h>
 #include <arch/transition.h>
+#include <assert.h>
 #include <console/console.h>
 
 /* Litte-endian, No XN-forced, Instr cache disabled,
@@ -66,8 +68,6 @@ void transition_with_entry(void *entry, void *arg, struct exc_state *exc_state)
 
 void transition(struct exc_state *exc_state)
 {
-	uint32_t scr_mask;
-	uint64_t hcr_mask;
 	uint64_t sctlr;
 	uint32_t current_el = get_current_el();
 
@@ -89,23 +89,27 @@ void transition(struct exc_state *exc_state)
 
 	if (elx->spsr & SPSR_ERET_32)
 		die("ARM64 Error: Do not support eret to Aarch32\n");
-	else {
-		scr_mask = SCR_LOWER_AARCH64;
-		hcr_mask = HCR_LOWER_AARCH64;
-	}
 
-	/* SCR: Write to SCR if current EL is EL3 */
-	if (current_el == EL3) {
-		uint32_t scr = raw_read_scr_el3();
-		scr |= scr_mask;
-		raw_write_scr_el3(scr);
-	}
-	/* HCR: Write to HCR if current EL is EL2 */
-	else if (current_el == EL2) {
-		uint64_t hcr = raw_read_hcr_el2();
-		hcr |= hcr_mask;
-		raw_write_hcr_el2(hcr);
-	}
+	/* Most parts of coreboot currently don't support EL2 anyway. */
+	assert(current_el == EL3);
+
+	/* Initialize SCR with defaults for running without secure monitor. */
+	raw_write_scr_el3(SCR_TWE_DISABLE |	/* don't trap WFE */
+			  SCR_TWI_DISABLE |	/* don't trap WFI */
+			  SCR_ST_ENABLE |	/* allow secure timer access */
+			  SCR_LOWER_AARCH64 |	/* lower level is AArch64 */
+			  SCR_SIF_DISABLE |	/* disable secure ins. fetch */
+			  SCR_HVC_ENABLE |	/* allow HVC instruction */
+			  SCR_SMD_ENABLE |	/* disable SMC instruction */
+			  SCR_RES1 |		/* reserved-1 bits */
+			  SCR_EA_DISABLE |	/* disable ext. abort trap */
+			  SCR_FIQ_DISABLE |	/* disable FIQ trap to EL3 */
+			  SCR_IRQ_DISABLE |	/* disable IRQ trap to EL3 */
+			  SCR_NS_ENABLE);	/* lower level is non-secure */
+
+	/* Initialize CPTR to not trap anything to EL3. */
+	raw_write_cptr_el3(CPTR_EL3_TCPAC_DISABLE | CPTR_EL3_TTA_DISABLE |
+			   CPTR_EL3_TFP_DISABLE);
 
 	/* ELR/SPSR: Write entry point and processor state of program */
 	raw_write_elr_current(elx->elr);
@@ -118,6 +122,7 @@ void transition(struct exc_state *exc_state)
 
 	/* SP_ELx: Initialize stack pointer */
 	raw_write_sp_elx(elx->sp_elx, elx_el);
+	isb();
 
 	/* Eret to the entry point */
 	trans_switch(regs);
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index c6e2a5387b..59b1317438 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -84,6 +84,7 @@ romstage-$(CONFIG_PRIMITIVE_MEMTEST) += primitive_memtest.c
 ramstage-$(CONFIG_PRIMITIVE_MEMTEST) += primitive_memtest.c
 romstage-$(CONFIG_CACHE_AS_RAM) += ramtest.c
 romstage-$(CONFIG_GENERIC_GPIO_LIB) += gpio.c
+romstage-y += stack.c
 
 ifeq ($(CONFIG_EARLY_CBMEM_INIT),y)
 romstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
diff --git a/src/soc/nvidia/tegra132/Kconfig b/src/soc/nvidia/tegra132/Kconfig
index 8473d4ac5b..04d57835d0 100644
--- a/src/soc/nvidia/tegra132/Kconfig
+++ b/src/soc/nvidia/tegra132/Kconfig
@@ -17,11 +17,6 @@ config SOC_NVIDIA_TEGRA132
 
 if SOC_NVIDIA_TEGRA132
 
-# TODO: Remove after replacing arch/arm64/stage_entry.S
-config STACK_SIZE
-	hex
-	default 0x1000
-
 config MAINBOARD_DO_DSI_INIT
 	bool "Use dsi graphics interface"
 	depends on MAINBOARD_DO_NATIVE_VGA_INIT
@@ -36,10 +31,6 @@ config MAINBOARD_DO_SOR_INIT
 	help
 	  Initialize dp display
 
-config MAX_CPUS
-	int
-	default 2
-
 config MTS_DIRECTORY
 	string "Directory where MTS microcode files are located"
 	default "3rdparty/blobs/cpu/nvidia/tegra132/current/prod"
diff --git a/src/soc/nvidia/tegra132/Makefile.inc b/src/soc/nvidia/tegra132/Makefile.inc
index 22ccba5626..b48fd3ab90 100644
--- a/src/soc/nvidia/tegra132/Makefile.inc
+++ b/src/soc/nvidia/tegra132/Makefile.inc
@@ -90,6 +90,7 @@ ramstage-y += ramstage.c
 ramstage-y += mmu_operations.c
 ramstage-$(CONFIG_DRIVERS_UART) += uart.c
 ramstage-y += ../tegra/usb.c
+ramstage-y += stage_entry.S
 
 modules_arm-y += monotonic_timer.c
 
diff --git a/src/soc/nvidia/tegra132/include/soc/memlayout.ld b/src/soc/nvidia/tegra132/include/soc/memlayout.ld
index d403c17127..aad3083132 100644
--- a/src/soc/nvidia/tegra132/include/soc/memlayout.ld
+++ b/src/soc/nvidia/tegra132/include/soc/memlayout.ld
@@ -14,6 +14,7 @@
  */
 
 #include <memlayout.h>
+#include <rules.h>
 
 #include <arch/header.ld>
 
@@ -29,7 +30,11 @@ SECTIONS
 	SRAM_START(0x40000000)
 	PRERAM_CBMEM_CONSOLE(0x40000000, 8K)
 	PRERAM_CBFS_CACHE(0x40002000, 84K)
-	STACK(0x40017000, 14K)
+#if ENV_ARM64
+	STACK(0x40017000, 8K)
+#else	/* AVP gets a separate stack to avoid any chance of handoff races. */
+	STACK(0x40019000, 6K)
+#endif
 	TIMESTAMP(0x4001A800, 2K)
 	BOOTBLOCK(0x4001B800, 22K)
 	ROMSTAGE(0x40021000, 124K)
diff --git a/src/soc/nvidia/tegra132/include/soc/memlayout_vboot2.ld b/src/soc/nvidia/tegra132/include/soc/memlayout_vboot2.ld
index 7a6a1688fb..e3d221ea75 100644
--- a/src/soc/nvidia/tegra132/include/soc/memlayout_vboot2.ld
+++ b/src/soc/nvidia/tegra132/include/soc/memlayout_vboot2.ld
@@ -14,6 +14,7 @@
  */
 
 #include <memlayout.h>
+#include <rules.h>
 
 #include <arch/header.ld>
 
@@ -29,8 +30,12 @@ SECTIONS
 	SRAM_START(0x40000000)
 	PRERAM_CBMEM_CONSOLE(0x40000000, 8K)
 	PRERAM_CBFS_CACHE(0x40002000, 72K)
-	VBOOT2_WORK(0x40014000, 16K)
-	STACK(0x40018000, 2K)
+	VBOOT2_WORK(0x40014000, 12K)
+#if ENV_ARM64
+	STACK(0x40017000, 3K)
+#else	/* AVP gets a separate stack to avoid any chance of handoff races. */
+	STACK(0x40017C00, 3K)
+#endif
 	TIMESTAMP(0x40018800, 2K)
 	BOOTBLOCK(0x40019000, 22K)
 	VERSTAGE(0x4001e800, 55K)
diff --git a/src/soc/nvidia/tegra132/maincpu.S b/src/soc/nvidia/tegra132/maincpu.S
deleted file mode 100644
index 898d821d7e..0000000000
--- a/src/soc/nvidia/tegra132/maincpu.S
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright 2013 Google Inc.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. The name of the author may not be used to endorse or promote products
- *    derived from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <arch/asm.h>
-
-ENTRY(maincpu_setup)
-	/*
-	 * Set the cpu to System mode with IRQ and FIQ disabled. Prefetch/Data
-	 * aborts may happen early and crash before the abort handlers are
-	 * installed, but at least the problem will show up near the code that
-	 * causes it.
-	 */
-	msr	cpsr, #0xdf
-
-	ldr	sp, maincpu_stack_pointer
-	eor	lr, lr
-	ldr	r0, maincpu_entry_point
-	bx	r0
-ENDPROC(maincpu_setup)
-
-	.align 2
-
-	.global maincpu_stack_pointer
-maincpu_stack_pointer:
-	.word 0
-
-	.global maincpu_entry_point
-maincpu_entry_point:
-	.word 0
diff --git a/src/soc/nvidia/tegra132/ramstage.c b/src/soc/nvidia/tegra132/ramstage.c
index ca9cec49c3..fec31c4686 100644
--- a/src/soc/nvidia/tegra132/ramstage.c
+++ b/src/soc/nvidia/tegra132/ramstage.c
@@ -14,6 +14,7 @@
  */
 
 #include <arch/stages.h>
+#include <gic.h>
 #include <soc/addressmap.h>
 #include <soc/clock.h>
 #include <soc/mc.h>
@@ -28,8 +29,14 @@ static void lock_down_vpr(void)
 	write32(&regs->video_protect_reg_ctrl, 1);
 }
 
-void arm64_soc_init(void)
+/* Tegra-specific entry point, called from assembly in stage_entry.S */
+void ramstage_entry(void);
+void ramstage_entry(void)
 {
+	/* TODO: Is this still needed? */
+	gic_init();
+
+	/* TODO: Move TrustZone setup to BL31? */
 	trustzone_region_init();
 
 	tegra132_mmu_init();
@@ -40,4 +47,7 @@ void arm64_soc_init(void)
 
 	/* Lock down VPR */
 	lock_down_vpr();
+
+	/* Jump to boot state machine in common code. */
+	main();
 }
diff --git a/src/soc/nvidia/tegra132/romstage.c b/src/soc/nvidia/tegra132/romstage.c
index a6753b3a87..3b45aff63d 100644
--- a/src/soc/nvidia/tegra132/romstage.c
+++ b/src/soc/nvidia/tegra132/romstage.c
@@ -19,6 +19,7 @@
 #include <cbmem.h>
 #include <console/cbmem_console.h>
 #include <console/console.h>
+#include <lib.h>
 #include <program_loading.h>
 #include <soc/addressmap.h>
 #include <soc/ccplex.h>
@@ -26,6 +27,7 @@
 #include <soc/sdram.h>
 #include <soc/sdram_configs.h>
 #include <soc/romstage.h>
+#include <symbols.h>
 #include <timer.h>
 #include <timestamp.h>
 
@@ -82,6 +84,9 @@ void romstage(void)
 
 void platform_prog_run(struct prog *prog)
 {
+	/* We'll switch to a new stack, so validate our old one here. */
+	checkstack(_estack, 0);
+
 	ccplex_cpu_start(prog_entry(prog));
 
 	clock_halt_avp();
diff --git a/src/arch/arm64/cpu/cortex_a57.S b/src/soc/nvidia/tegra132/stage_entry.S
index 80707caadf..de89f9514f 100644
--- a/src/arch/arm64/cpu/cortex_a57.S
+++ b/src/soc/nvidia/tegra132/stage_entry.S
@@ -14,12 +14,11 @@
  */
 
 #include <arch/asm.h>
-#include <cpu/cortex_a57.h>
 
-ENTRY(arm64_cpu_early_setup)
-	mrs x0, CPUECTLR_EL1
-	orr x0, x0, #(1 << SMPEN_SHIFT)
-	msr CPUECTLR_EL1, x0
-	isb
-	ret
-ENDPROC(arm64_cpu_early_setup)
+ENTRY(stage_entry)
+	/* Initialize PSTATE, SCTLR and caches to clean state, set up stack. */
+	bl	arm64_init_cpu
+
+	/* Jump to Tegra-specific C entry point. */
+	bl	ramstage_entry
+ENDPROC(stage_entry)
diff --git a/src/soc/nvidia/tegra210/Kconfig b/src/soc/nvidia/tegra210/Kconfig
index 002a6d3806..5273d81782 100644
--- a/src/soc/nvidia/tegra210/Kconfig
+++ b/src/soc/nvidia/tegra210/Kconfig
@@ -6,7 +6,6 @@ config SOC_NVIDIA_TEGRA210
 	select ARCH_VERSTAGE_ARMV4
 	select ARCH_ROMSTAGE_ARMV4
 	select ARCH_RAMSTAGE_ARMV8_64
-	select ARCH_ARM64_CPU_CORTEX_A57
 	select BOOTBLOCK_CONSOLE
 	select GIC
 	select HAVE_MONOTONIC_TIMER
@@ -22,11 +21,6 @@ if SOC_NVIDIA_TEGRA210
 config CHROMEOS
 	select CHROMEOS_RAMOOPS_NON_ACPI
 
-# TODO: Remove after replacing arch/arm64/stage_entry.S
-config STACK_SIZE
-	hex
-	default 0x1000
-
 config MAINBOARD_DO_DSI_INIT
 	bool "Use dsi graphics interface"
 	depends on MAINBOARD_DO_NATIVE_VGA_INIT
@@ -41,10 +35,6 @@ config MAINBOARD_DO_SOR_INIT
 	help
 	  Initialize dp display
 
-config MAX_CPUS
-	int
-	default 4
-
 choice CONSOLE_SERIAL_TEGRA210_UART_CHOICES
 	prompt "Serial Console UART"
 	default CONSOLE_SERIAL_TEGRA210_UARTA
diff --git a/src/soc/nvidia/tegra210/cpu.c b/src/soc/nvidia/tegra210/cpu.c
index a837a99cc0..0303150ac6 100644
--- a/src/soc/nvidia/tegra210/cpu.c
+++ b/src/soc/nvidia/tegra210/cpu.c
@@ -23,7 +23,7 @@
 
 static void enable_core_clocks(int cpu)
 {
-	const uint32_t cpu_clocks[CONFIG_MAX_CPUS] = {
+	const uint32_t cpu_clocks[] = {
 		[0] = CRC_RST_CPUG_CLR_CPU0 | CRC_RST_CPUG_CLR_DBG0 |
 		CRC_RST_CPUG_CLR_CORE0 | CRC_RST_CPUG_CLR_CX0,
 		[1] = CRC_RST_CPUG_CLR_CPU1 | CRC_RST_CPUG_CLR_DBG1 |
diff --git a/src/soc/nvidia/tegra210/include/soc/memlayout.ld b/src/soc/nvidia/tegra210/include/soc/memlayout.ld
index 0338cd9604..00ecd28224 100644
--- a/src/soc/nvidia/tegra210/include/soc/memlayout.ld
+++ b/src/soc/nvidia/tegra210/include/soc/memlayout.ld
@@ -14,6 +14,7 @@
  */
 
 #include <memlayout.h>
+#include <rules.h>
 
 #include <arch/header.ld>
 
@@ -29,7 +30,11 @@ SECTIONS
 	SRAM_START(0x40000000)
 	PRERAM_CBMEM_CONSOLE(0x40000000, 8K)
 	PRERAM_CBFS_CACHE(0x40002000, 84K)
-	STACK(0x40017000, 16K)
+#if ENV_ARM64
+	STACK(0x40017000, 8K)
+#else	/* AVP gets a separate stack to avoid any chance of handoff races. */
+	STACK(0x40019000, 8K)
+#endif
 	TIMESTAMP(0x4001B000, 2K)
 	BOOTBLOCK(0x4001B800, 24K)
 	ROMSTAGE(0x40022000, 120K)
diff --git a/src/soc/nvidia/tegra210/include/soc/memlayout_vboot2.ld b/src/soc/nvidia/tegra210/include/soc/memlayout_vboot2.ld
index b4b3dc2822..c1c581bf71 100644
--- a/src/soc/nvidia/tegra210/include/soc/memlayout_vboot2.ld
+++ b/src/soc/nvidia/tegra210/include/soc/memlayout_vboot2.ld
@@ -14,6 +14,7 @@
  */
 
 #include <memlayout.h>
+#include <rules.h>
 
 #include <arch/header.ld>
 
@@ -29,8 +30,12 @@ SECTIONS
 	SRAM_START(0x40000000)
 	PRERAM_CBMEM_CONSOLE(0x40000000, 8K)
 	PRERAM_CBFS_CACHE(0x40002000, 36K)
-	VBOOT2_WORK(0x4000B000, 16K)
-	STACK(0x4000F000, 2K)
+	VBOOT2_WORK(0x4000B000, 12K)
+#if ENV_ARM64
+	STACK(0x4000E000, 3K)
+#else	/* AVP gets a separate stack to avoid any chance of handoff races. */
+	STACK(0x4000EC00, 3K)
+#endif
 	TIMESTAMP(0x4000F800, 2K)
 	BOOTBLOCK(0x40010000, 28K)
 	VERSTAGE(0x40017000, 64K)
diff --git a/src/soc/nvidia/tegra210/maincpu.S b/src/soc/nvidia/tegra210/maincpu.S
deleted file mode 100644
index 898d821d7e..0000000000
--- a/src/soc/nvidia/tegra210/maincpu.S
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright 2013 Google Inc.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. The name of the author may not be used to endorse or promote products
- *    derived from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <arch/asm.h>
-
-ENTRY(maincpu_setup)
-	/*
-	 * Set the cpu to System mode with IRQ and FIQ disabled. Prefetch/Data
-	 * aborts may happen early and crash before the abort handlers are
-	 * installed, but at least the problem will show up near the code that
-	 * causes it.
-	 */
-	msr	cpsr, #0xdf
-
-	ldr	sp, maincpu_stack_pointer
-	eor	lr, lr
-	ldr	r0, maincpu_entry_point
-	bx	r0
-ENDPROC(maincpu_setup)
-
-	.align 2
-
-	.global maincpu_stack_pointer
-maincpu_stack_pointer:
-	.word 0
-
-	.global maincpu_entry_point
-maincpu_entry_point:
-	.word 0
diff --git a/src/soc/nvidia/tegra210/ramstage.c b/src/soc/nvidia/tegra210/ramstage.c
index 5c375106a2..18fdded800 100644
--- a/src/soc/nvidia/tegra210/ramstage.c
+++ b/src/soc/nvidia/tegra210/ramstage.c
@@ -16,12 +16,13 @@
 #include <arch/clock.h>
 #include <arch/cpu.h>
 #include <arch/stages.h>
+#include <gic.h>
 #include <soc/addressmap.h>
 #include <soc/clock.h>
 #include <soc/mmu_operations.h>
 #include <soc/mtc.h>
 
-void arm64_arch_timer_init(void)
+static void arm64_arch_timer_init(void)
 {
 	uint32_t freq = clock_get_osc_khz() * 1000;
 	// Set the cntfrq register.
@@ -47,11 +48,20 @@ static void mselect_enable_wrap(void)
 	write32((void *)TEGRA_MSELECT_CONFIG, reg);
 }
 
-void arm64_soc_init(void)
+/* Tegra-specific entry point, called from assembly in stage_entry.S */
+void ramstage_entry(void);
+void ramstage_entry(void)
 {
+	/* TODO: Is this still needed? */
+	gic_init();
+
+	/* TODO: Move arch timer setup to BL31? */
+	arm64_arch_timer_init();
+
 	/* Enable WRAP to INCR burst type conversion in MSELECT */
 	mselect_enable_wrap();
 
+	/* TODO: Move TrustZone setup to BL31? */
 	trustzone_region_init();
 
 	tegra210_mmu_init();
@@ -60,4 +70,7 @@ void arm64_soc_init(void)
 
 	if (tegra210_run_mtc() != 0)
 		printk(BIOS_ERR, "MTC: No training data.\n");
+
+	/* Jump to boot state machine in common code. */
+	main();
 }
diff --git a/src/soc/nvidia/tegra210/romstage.c b/src/soc/nvidia/tegra210/romstage.c
index 23c526613c..c9ff35bfb5 100644
--- a/src/soc/nvidia/tegra210/romstage.c
+++ b/src/soc/nvidia/tegra210/romstage.c
@@ -19,6 +19,7 @@
 #include <cbmem.h>
 #include <console/cbmem_console.h>
 #include <console/console.h>
+#include <lib.h>
 #include <program_loading.h>
 #include <soc/addressmap.h>
 #include <soc/ccplex.h>
@@ -27,6 +28,7 @@
 #include <soc/sdram_configs.h>
 #include <soc/romstage.h>
 #include <soc/nvidia/tegra/apbmisc.h>
+#include <symbols.h>
 #include <timer.h>
 #include <timestamp.h>
 #include <vendorcode/google/chromeos/chromeos.h>
@@ -86,6 +88,9 @@ void romstage(void)
 
 void platform_prog_run(struct prog *prog)
 {
+	/* We'll switch to a new stack, so validate our old one here. */
+	checkstack(_estack, 0);
+
 	ccplex_cpu_start(prog_entry(prog));
 
 	clock_halt_avp();
diff --git a/src/soc/nvidia/tegra210/stage_entry.S b/src/soc/nvidia/tegra210/stage_entry.S
index f5dabcb371..0eeffce2da 100644
--- a/src/soc/nvidia/tegra210/stage_entry.S
+++ b/src/soc/nvidia/tegra210/stage_entry.S
@@ -82,10 +82,10 @@
 
 ENTRY(stage_entry)
 	t210_a57_fixup
-	b	arm64_cpu_startup
-ENDPROC(stage_entry)
 
-ENTRY(tegra210_reset_handler)
-	t210_a57_fixup
-	b	arm64_cpu_startup_resume
-ENDPROC(tegra210_reset_handler)
+	/* Initialize PSTATE, SCTLR and caches to clean state, set up stack. */
+	bl	arm64_init_cpu
+
+	/* Jump to Tegra-specific C entry point. */
+	bl	ramstage_entry
+ENDPROC(stage_entry)