linux-kernel - Re: [RESEND PATCH] ARM: EXYNOS: Fix failed second suspend on Exynos4

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Date:	Mon, 23 Feb 2015 17:25:48 +0100
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	stable@...r.kernel.org, Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [RESEND PATCH] ARM: EXYNOS: Fix failed second suspend on Exynos4


Hi,

On Wednesday, February 18, 2015 11:45:25 AM Krzysztof Kozlowski wrote:
> 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.
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> Fixes: 13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off")
> Cc: <stable@...r.kernel.org>

It turned out that this patch is also needed to fix cpuidle AFTR mode
hang on Trats2.

Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

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