linux-kernel - Re: [PATCH V5 1/3] arm: dts: dra7: Add crossbar device binding

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Date:	Tue, 6 May 2014 15:07:50 -0500
From:	Darren Etheridge <detheridge@...com>
To:	Nishanth Menon <nm@...com>
CC:	<balbi@...com>, Sricharan R <r.sricharan@...com>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-doc@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linus.walleij@...aro.org>,
	<linux@....linux.org.uk>, <tony@...mide.com>, <rnayak@...com>,
	<marc.zyngier@....com>, <grant.likely@...aro.org>,
	<mark.rutland@....com>, <tglx@...utronix.de>,
	<galak@...eaurora.org>, <santosh.shilimkar@...com>,
	<bcousson@...libre.com>, <robherring2@...il.com>
Subject: Re: [PATCH V5 1/3] arm: dts: dra7: Add crossbar device binding

Darren Etheridge <detheridge@...com> wrote on Tue [2014-May-06 14:58:04 -0500]:
> Nishanth Menon <nm@...com> wrote on Tue [2014-May-06 14:46:10 -0500]:
> > On 05/06/2014 02:40 PM, Felipe Balbi wrote:
> > > On Tue, May 06, 2014 at 07:26:17PM +0530, Sricharan R wrote:
> > >> This adds the irq crossbar device node.
> > >>
> > >> There is a IRQ crossbar device in the soc, which
> > >> maps the irq requests from the peripherals to the
> > >> mpu interrupt controller's inputs. The Peripheral irq
> > >> requests are connected to only one crossbar
> > >> input and the output of the crossbar is connected to only one
> > >> controller's input line. The crossbar device is used to map
> > >> a peripheral input to a free mpu's interrupt controller line.
> > >>
> > >> Cc: Benoit Cousson <bcousson@...libre.com>
> > >> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
> > >> Cc: Rajendra Nayak <rnayak@...com>
> > >> Cc: Tony Lindgren <tony@...mide.com>
> > >> Signed-off-by: Sricharan R <r.sricharan@...com>
> > >> Signed-off-by: Nishanth Menon <nm@...com>
> > >> ---
> > >> [V5] Rebased on top of 3.15-rc4 and corrected the
> > >>      irqs-reserved list
> > >>
> > >>  arch/arm/boot/dts/dra7.dtsi |    8 ++++++++
> > >>  1 file changed, 8 insertions(+)
> > >>
> > >> diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi
> > >> index 149b550..0274a86 100644
> > >> --- a/arch/arm/boot/dts/dra7.dtsi
> > >> +++ b/arch/arm/boot/dts/dra7.dtsi
> > >> @@ -790,6 +790,14 @@
> > >>  			status = "disabled";
> > >>  		};
> > >>  	};
> > >> +
> > >> +	crossbar_mpu: crossbar@...20000 {
> > > 
> > > shouldn't this be "status = disabled"; so that boards enable this
> > > on-demand ??
> > > 
> > It cannot be and does not need to be. crossbar is an SoC feature. by
> > defining crossbar, the IRQ numbers we provide in DTS now becomes
> > crossbar numbers which get mapped to GIC interrupt numbers dynamically.
> > 
> > further crossbar is not a board feature. it is as ingrained in DRA7
> > behavior as GIC is. we are fortunate that we have some default mapping
> > of crossbar that allows the current peripherals to work, with this
> > support, we dont have to depend any longer on "we are lucky that is
> > mapped".
> > 
> > That said, in hindsight, patch #1 and 2 should be squashed IMHO. else
> > we have a bisectability problem here.
> > 
> Yes the bisectability problem is completely true - I was just testing
> that as your email came in.  In fact I think all three patches need to
> be squashed into one, I can't boot the dra7-EVM unless I have all three
> patches applied.
> 

Or I just tried reordering, so patch 3/3 becomes patch 1 and then squash
patch 1/3 and patch 2/3 together to form patch 2.  That seems to at
least let the kernel boot to completion.

Darren
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