linux-kernel - Re: [PATCH v7 1/9] arm64: dts: exynos: Add dts files for 64-bit Exynos5433 SoC

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Date:	Thu, 2 Apr 2015 18:35:58 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	"kgene@...nel.org" <kgene@...nel.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"arnd@...db.de" <arnd@...db.de>, "olof@...om.net" <olof@...om.net>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"inki.dae@...sung.com" <inki.dae@...sung.com>,
	"chanho61.park@...sung.com" <chanho61.park@...sung.com>,
	"sw0312.kim@...sung.com" <sw0312.kim@...sung.com>,
	"jh80.chung@...sung.com" <jh80.chung@...sung.com>,
	"ideal.song@...sung.com" <ideal.song@...sung.com>,
	"a.kesavan@...sung.com" <a.kesavan@...sung.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 1/9] arm64: dts: exynos: Add dts files for 64-bit
 Exynos5433 SoC

On Tue, Mar 31, 2015 at 12:56:38AM +0100, Chanwoo Choi wrote:
> Hi Mark,
> 
> On 03/31/2015 01:09 AM, Mark Rutland wrote:
> > Hi,
> > 
> > On Wed, Mar 18, 2015 at 12:17:28AM +0000, Chanwoo Choi wrote:
> >> This patch adds new Exynos5433 dtsi to support 64-bit Exynos5433 SoC based on
> >> Octal core CPUs (quad Cortex-A57 and quad Cortex-A53). And Exynos5433 supports
> >> PSCI (Power State Coordination Interface) v0.1.
> >>
> >> This patch includes following dt node to support Exynos5433 SoC:
> >> 1. Octa core for big.LITTLE architecture
> >> - Cortex-A53 LITTLE Quad-core
> >> - Cortex-A57 big Quad-core
> >> - Support PSCI v0.1
> > 
> > Is CPU0 hotplug still broken, or has the FW been fixed?
> 
> CPU0 hotplug is still not working.
> 
> > 
> > I'm very worried about adding a DT that's known broken, especially when
> > we have no idea as to if/when the FW will be fixed judging from prior
> > replies.
> 
> As I replied, I can not fix the FW because I don't have any code of FW.

Surely you are able to contact those who do?

> I don't have any solution to fix it on Linux kernel level.
> 
> So, If you agree, I can add the comment of CPU0 hotplug issue on DT file.

I disagree. I do not want to add a DT that is known to be broken;
especially when we have no idea how to fix it. It creates long-term
maintenance pain for everyone, and marginal gain for few. A comment does
nothing to aid the end-user.

So NAK to the PSCI node and PSCI enable method in this dts until we
either have a working firmware, or a reasonable mechanism to handle the
deficiency.

Mark.
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