Date:	Wed, 18 Mar 2015 03:05:20 +0900
From:	Kukjin Kim <kgene@...nel.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
CC:	Kukjin Kim <kgene@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Olof Johansson <olof@...om.net>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	stable@...r.kernel.org,
	BartlomiejZolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v2] ARM: EXYNOS: Fix failed second suspend on Exynos4

On 03/11/15 19:29, Krzysztof Kozlowski wrote:
> On śro, 2015-03-11 at 11:20 +0100, 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>
>> Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
>> Tested-by: Chanwoo Choi <cw00.choi@...sung.com>
> 
> Dear Kukjin,
> 
> This patch was first sent on 3rd of February. It could enter before
> opening 4.0 merge window. I did not receive any response from you in
> that time.
> 
> So let me point next steps:
> 1. The Exynos4412 suspend on 4.0 is broken and now this patch applies as
> a fix.
> 2. I resent it on 18th of February.
> 3. I received tested-by from Bartlomiej and Chanwoo.
> 4. Bartlomiej pinged you on 3rd March.
> 
> Still no response. If the patch does not look good then please share
> your comments. I'll fix it.
> If this patch looks good, why does it take so much time?
> 

Please use another way something like check ARM core rather than use
'soc_is_xxx()', as you know it is not acceptable now even it is just
moving/modifying exist function though.

And please make sure your updates don't hurt other exynos5 stuff. Any
tests on exynos5 platforms would be helpful.

And I don't think the fix should be sent to 'stable' because I can't see
the 'add node for L2$ controller' in v3.19...looks applied from v4.0-rc...

One more if you have any doubts, I'd like to ask you to contact S.LSI
guys who have created the vendor codes not assume with the code because
maybe the vendor code you mentioned cannot cover all exynos stuff I
think. Then we could make more clear pm codes in mainline. To be honest
I'm not a Power Management hardware guy so I don't know every regarding
PM stuff in exynos SoCs, I can contact them easier though...I mean
please don't assume any hardware behavior with just vendor code. Please
ask, you have an access in Samsung intranet before posting something
like this...Hope let's make a better fix together during -rc.

Thanks,
Kukjin
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