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, 27 insertions, 0 deletions

diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index bcde0dd668df..c3bfbba3006d 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -167,6 +167,33 @@ static void __init exynos_init_io(void)
 }
 
 /*
+ * Set or clear the USE_DELAYED_RESET_ASSERTION option. Used by smp code
+ * and suspend.
+ *
+ * This is necessary only on Exynos4 SoCs. When system is running
+ * USE_DELAYED_RESET_ASSERTION should be set so the ARM CLK clock down
+ * feature could properly detect global idle state when secondary CPU is
+ * powered down.
+ *
+ * However this should not be set when such system is going into suspend.
+ */
+void exynos_set_delayed_reset_assertion(bool enable)
+{
+	if (soc_is_exynos4()) {
+		unsigned int tmp, core_id;
+
+		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
+			tmp = pmu_raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
+			if (enable)
+				tmp |= S5P_USE_DELAYED_RESET_ASSERTION;
+			else
+				tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
+			pmu_raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
+		}
+	}
+}
+
+/*
  * Apparently, these SoCs are not able to wake-up from suspend using
  * the PMU. Too bad. Should they suddenly become capable of such a
  * feat, the matches below should be moved to suspend.c.