linux-kernel - Re: [PATCH v2] arm64: ARM: Fix the Generic Timers interrupt active level description

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Date:	Fri, 28 Nov 2014 10:38:43 +0000
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Jisheng Zhang <jszhang@...vell.com>
Cc:	Marc Zyngier <Marc.Zyngier@....com>, Arnd Bergmann <arnd@...db.de>,
	Olof Johansson <olof@...om.net>,
	Mark Rutland <Mark.Rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] arm64: ARM: Fix the Generic Timers interrupt active
 level description

On Fri, Nov 28, 2014 at 03:12:52AM +0000, Jisheng Zhang wrote:
> Dear Marc and Liviu,
> 
> On Thu, 27 Nov 2014 10:39:28 -0800
> Marc Zyngier <marc.zyngier@....com> wrote:
> 
> > On 27/11/14 16:21, Liviu Dudau wrote:
> > > The Cortex-A5x TRM states in paragraph "9.2 Generic Timer functional
> > > description" that generic timers provide a level not edge interrupt
> > > output. Fix the device trees to correctly describe this.
> > > 
> > > While doing this update the CPU mask to match the number of described
> > > CPUs as well as the DT bindings documentation for Generic Timers.
> > > 
> > > Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> > 
> > Acked-by: Marc Zyngier <marc.zyngier@....com>
> > 
> > 	M.
> > 
> > > ---
> > > 
> > > Arnd, Olof: This is on top of linux-next/master as it patches Juno's
> > > as well as all the other ARM DTs.
> > > 
> > > --
> > > 
> > >  Documentation/devicetree/bindings/arm/arch_timer.txt | 8 ++++----
> > >  arch/arm64/boot/dts/arm/foundation-v8.dts            | 8 ++++----
> > >  arch/arm64/boot/dts/arm/juno.dts                     | 8 ++++----
> > >  arch/arm64/boot/dts/arm/rtsm_ve-aemv8a.dts           | 8 ++++----
> > >  4 files changed, 16 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt
> > > b/Documentation/devicetree/bindings/arm/arch_timer.txt index
> > > 37b2caf..6d2aa87 100644 ---
> > > a/Documentation/devicetree/bindings/arm/arch_timer.txt +++
> > > b/Documentation/devicetree/bindings/arm/arch_timer.txt @@ -27,10 +27,10
> > > @@ Example: timer {
> > >  		compatible = "arm,cortex-a15-timer",
> > >  			     "arm,armv7-timer";
> > > -		interrupts = <1 13 0xf08>,
> > > -			     <1 14 0xf08>,
> > > -			     <1 11 0xf08>,
> > > -			     <1 10 0xf08>;
> > > +		interrupts = <1 13 0xf04>,
> > > +			     <1 14 0xf04>,
> > > +			     <1 11 0xf04>,
> > > +			     <1 10 0xf04>;
> > >  		clock-frequency = <100000000>;
> > >  	};
> > >  
> 
> Does it mean we also need to fix the interrupt level description under
> arch/arm/boot/dts? I found they are also wrong or I misunderstand something?

Hi Jisheng,

It looks like Marc and I managed to confuse ourselves. The TRM for GIC-500 and
GIC-400 (basically covering most of GICv1 and > GICv2) clearly says that for *PPIs*
the level triggered interrupts are active-LOW.

So, this patch is invalid and my v1 version is correct, but Marc tells that in
that case the GIC driver needs patching (which I'm going to look into).

Best regards,
Liviu

> 
> Thanks,
> Jisheng
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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