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[U-Boot,v4,09/10] Exynos542x: Make A7s boot with thumb-mode U-Boot on warm reset

Message ID 1424419040-28768-10-git-send-email-akshay.s@samsung.com
State Accepted
Delegated to: Minkyu Kang
Headers show

Commit Message

Akshay Saraswat Feb. 20, 2015, 7:57 a.m. UTC 
On warm reset, all cores jump to the low_power_start function because iRAM
data is retained and because while executing iROM code all cores find
the jump flag 0x02020028 set. In low_power_start, cores check the reset
status and if true they clear the jump flag and jump back to 0x0.

The A7 cores do jump to 0x0 but consider following instructions as a Thumb
instructions which in turn makes them loop inside the iROM code instead of
jumping to power_down_core.

This issue is fixed by replacing the "mov pc" instruction with a "bx"
instruction which switches state along with the jump to make the execution
unit consider the branch target as an ARM instruction.

Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
---
Changes since v3:
	- No change.

Changes since v2:
	- No change.

Changes since v1:
	- Added Reviewed-by & Tested-by.

 arch/arm/cpu/armv7/exynos/lowlevel_init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/arch/arm/cpu/armv7/exynos/lowlevel_init.c b/arch/arm/cpu/armv7/exynos/lowlevel_init.c
index 782ecd1..329ab0c 100644
--- a/arch/arm/cpu/armv7/exynos/lowlevel_init.c
+++ b/arch/arm/cpu/armv7/exynos/lowlevel_init.c
@@ -103,7 +103,7 @@  static void low_power_start(void)
 	reg_val = readl(EXYNOS5420_SPARE_BASE);
 	if (reg_val != CPU_RST_FLAG_VAL) {
 		writel(0x0, CONFIG_LOWPOWER_FLAG);
-		set_pc(0x0);
+		branch_bx(0x0);
 	}
 
 	reg_val = readl(CONFIG_PHY_IRAM_BASE + 0x4);