[U-Boot] [PATCH] ARM: tegra: implement WAR for Tegra114 CPU reset vector

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

A Tegra114 HW bug prevents the main CPU vector from being modified under
certain circumstances. Tegra114 A01P and later with a patched boot ROM
set the CPU reset vector to 0x4003fffc (end of IRAM). This allows placing
an arbitrary jump instruction at that location, in order to redirect to
the desired reset vector location. Modify Tegra114's start_cpu() to make
use of this feature. This allows CPUs with the patched boot ROM to boot.

Based-on-work-by: Jimmy Zhang <jimmzhang at nvidia.com>.
Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
 arch/arm/cpu/arm720t/tegra114/cpu.c |   36 +++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/arch/arm/cpu/arm720t/tegra114/cpu.c b/arch/arm/cpu/arm720t/tegra114/cpu.c
index 5962e15..429ac94 100644
--- a/arch/arm/cpu/arm720t/tegra114/cpu.c
+++ b/arch/arm/cpu/arm720t/tegra114/cpu.c
@@ -269,6 +269,8 @@ void powerup_cpus(void)
 
 void start_cpu(u32 reset_vector)
 {
+	u32 imme, inst;
+
 	debug("start_cpu entry, reset_vector = %x\n", reset_vector);
 
 	t114_init_clocks();
@@ -285,12 +287,38 @@ void start_cpu(u32 reset_vector)
 	/* Take CPU(s) out of reset */
 	remove_cpu_resets();
 
+	/* Set the entry point for CPU execution from reset */
+
 	/*
-	 * Set the entry point for CPU execution from reset,
-	 *  if it's a non-zero value.
+	 * A01P with patched boot ROM; vector hard-coded to 0x4003fffc.
+	 * See nvbug 1193357 for details.
 	 */
-	if (reset_vector)
-		writel(reset_vector, EXCEP_VECTOR_CPU_RESET_VECTOR);
+
+	/* mov r0, #lsb(reset_vector) */
+	imme = reset_vector & 0xffff;
+	inst = imme & 0xfff;
+	inst |= ((imme >> 12) << 16);
+	inst |= 0xe3000000;
+	writel(inst, 0x4003fff0);
+
+	/* movt r0, #msb(reset_vector) */
+	imme = (reset_vector >> 16) & 0xffff;
+	inst = imme & 0xfff;
+	inst |= ((imme >> 12) << 16);
+	inst |= 0xe3400000;
+	writel(inst, 0x4003fff4);
+
+	/* bx r0 */
+	writel(0xe12fff10, 0x4003fff8);
+
+	/* b -12 */
+	imme = (u32)-20;
+	inst = (imme >> 2) & 0xffffff;
+	inst |= 0xea000000;
+	writel(inst, 0x4003fffc);
+
+	/* Write to orignal location for compatibility */
+	writel(reset_vector, EXCEP_VECTOR_CPU_RESET_VECTOR);
 
 	/* If the CPU(s) don't already have power, power 'em up */
 	powerup_cpus();
-- 
1.7.10.4