ARM: EXYNOS: Fix failed second suspend on Exynos4

On Exynos4412 boards (Trats2, Odroid U3) after enabling L2 cache in
56b60b8bce4a ("ARM: 8265/1: dts: exynos4: Add nodes for L2 cache
controller") the second suspend to RAM failed. First suspend worked fine
but the next one hang just after powering down of secondary CPUs (system
consumed energy as it would be running but was not responsive).

The issue was caused by enabling delayed reset assertion for CPU0 just
after issuing power down of cores. This was introduced for Exynos4 in
13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off").

The whole behavior is not well documented but after checking with vendor
code this should be done like this (on Exynos4):
1. Enable delayed reset assertion when system is running (for all CPUs).
2. Disable delayed reset assertion before suspending the system.
   This can be done after powering off secondary CPUs.
3. Re-enable the delayed reset assertion when system is resumed.

Fixes: 13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arm/mach-exynos/common.h b/arch/arm/mach-exynos/common.h
index acd5b560b728..5f5cd562c593 100644
--- a/arch/arm/mach-exynos/common.h
+++ b/arch/arm/mach-exynos/common.h
@@ -159,6 +159,8 @@ extern void exynos_enter_aftr(void);
 
 extern struct cpuidle_exynos_data cpuidle_coupled_exynos_data;
 
+extern void exynos_set_delayed_reset_assertion(bool enable);
+
 extern void s5p_init_cpu(void __iomem *cpuid_addr);
 extern unsigned int samsung_rev(void);
 extern void __iomem *cpu_boot_reg_base(void);