t210: Apply A57 hardware issue workaround during cpu startup

Define custom stage_entry to apply workaround for A57 hardware issue
for power on reset. It is observed that BTB contains stale data after
power on reset. This could lead to unexpected branching and crashes at
random intervals during the boot flow. Thus, invalidate the BTB
immediately after power on reset.

BUG=chrome-os-partner:41877
BRANCH=None
TEST=Compiles successfully and reboot test does not crash in firmware
for 10K iterations.

Change-Id: Ifbc9667bc5556112374f35733192b67b64a345d2
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: bc7c2fec3c6b29e291235669ba9f22ff611064a7
Original-Change-Id: I1f5714074afdfee64b88cea8a394936ca848634b
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/284869
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Trybot-Ready: Furquan Shaikh <furquan@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/10899
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

2 files changed, 29 insertions, 8 deletions

diff --git a/src/soc/nvidia/tegra210/Makefile.inc b/src/soc/nvidia/tegra210/Makefile.inc
index 3b2dc7c..8d7e1fc 100644
--- a/src/soc/nvidia/tegra210/Makefile.inc
+++ b/src/soc/nvidia/tegra210/Makefile.inc
@@ -101,13 +101,14 @@ ramstage-$(CONFIG_DRIVERS_UART) += uart.c
 ramstage-y += ../tegra/usb.c
 ramstage-$(CONFIG_ARM64_USE_SECURE_MONITOR) += secmon.c
 ramstage-$(CONFIG_HAVE_MTC) += mtc.c
+ramstage-y += stage_entry.S
 
 secmon-y += cpu.c
 secmon-y += cpu_lib.S
 secmon-y += flow_ctrl.c
 secmon-y += power.c
 secmon-y += psci.c
-secmon-y += reset_handler.S
+secmon-y += stage_entry.S
 secmon-y += uart.c
 secmon-y += gic.c
 
diff --git a/src/soc/nvidia/tegra210/reset_handler.S b/src/soc/nvidia/tegra210/stage_entry.S
index 53622b1..ee0265f 100644
--- a/src/soc/nvidia/tegra210/reset_handler.S
+++ b/src/soc/nvidia/tegra210/stage_entry.S
@@ -1,5 +1,8 @@
 /*
+ * This file is part of the coreboot project.
+ *
  * Copyright (c) 2015, NVIDIA CORPORATION.  All rights reserved.
+ * 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
@@ -9,19 +12,27 @@
  * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <arch/asm.h>
+#include <cpu/cortex_a57.h>
 
-#define CPUACTLR_EL1 s3_1_c15_c2_0
-
-CPU_RESET_ENTRY(tegra210_reset_handler)
+/*
+ * It is observed that BTB contains stale data after power on reset. This could
+ * lead to unexpected branching and crashes at random intervals during the boot
+ * flow. Thus, invalidate the BTB immediately after power on reset.
+ */
+.macro t210_a57_fixup
 	/*
 	 * Invalidate BTB along with I$ to remove any stale entries
 	 * from the branch predictor array.
 	 */
 	mrs	x0, CPUACTLR_EL1
-	orr	x0, x0, #1
+	orr	x0, x0, #BTB_INVALIDATE
 	msr	CPUACTLR_EL1, x0	/* invalidate BTB and I$ together */
 	dsb	sy
 	isb
@@ -29,7 +40,7 @@ CPU_RESET_ENTRY(tegra210_reset_handler)
 	dsb	sy
 	isb
 
-	bic	x0, x0, #1
+	bic	x0, x0, #BTB_INVALIDATE
 	msr	CPUACTLR_EL1, x0	/* restore original CPUACTLR_EL1 */
 	dsb	sy
 	isb
@@ -47,7 +58,7 @@ CPU_RESET_ENTRY(tegra210_reset_handler)
 	and	x0, x0, #2		/* extract oslk bit */
 	mrs	x1, mpidr_el1
 	bics	xzr, x0, x1, lsr #7	/* 0 if slow cluster */
-	b.eq	__restore_oslock
+	b.eq	1000f
 	mov	x0, xzr
 	msr	oslar_el1, x0		/* os lock stays 0 across warm reset */
 	mov	x3, #3
@@ -67,9 +78,18 @@ CPU_RESET_ENTRY(tegra210_reset_handler)
 	nop
 	.endr
 
-__restore_oslock:
+1000:
+	/* Restore os lock */
 	mov	x0, #1
 	msr	oslar_el1, x0
+.endm
+
+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)