Re: [PATCH 0/1] ARM: dts: exynos: Add timer node for exynos5420

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

On 04.04.2016 05:39, Adel Belhouane wrote:
> Le 29/03/2016 12:06, Krzysztof Kozlowski a écrit :
>> Please look at this thread:
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/359806.html
>>
>> Unfortunately I do not have any more details about this.
> 
> So I understand MCT and Arch Timer use the same hardware timer and
> there were issues when the MCT interface reset it at boot and during
> resume and the Arch Timer consumers didn't expect it. In this thread there
> were links [1] to a patch to have the MCT not writing the timer anymore,
> thus allowing the two interfaces to co-exist.
> 
> This patch was applied in commit 1d80415db64b. So no problem is to be
> expected when using both interfaces at the same time.
> 
> I can see  exynos5250 got its Arch Timer definition for KVM:
> 
> - From the description of commit 2b7da98870bc
> ARM: dts: Add architected timer nodes for exynos5250
> [...]
> This is required by KVM.
> 
> So is there something else blocking adding this definition for 542x/5800
> considering its effect is enabling KVM ?

Yeah, this is blocking:
> Doug Anderson:
> According to Samsung, there are issues where using cp15 could
> sometimes return the wrong value, especially if you happen to read it
> while on an A7 instead of an A15.

> Kukjin Kim:
> One more thing, if you change it for your own private platform, it's > up
> to you but if not, i.e., for mass product, please don't change it.
> Because it's not guaranteed even you haven't seen its failure...

Best regards,
Krzysztof