Subject: Re: [RFC] irqchip: add support for LS1021A external interrupt lines
From: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
To: Alexander Stein <alexander.stein@systec-electronic.com>
CC: Marc Zyngier <marc.zyngier@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>
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Date: Mon, 11 Dec 2017 15:06:52 +0100
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On 2017-12-11 14:45, Rasmus Villemoes wrote:
> On 2017-12-11 11:02, Alexander Stein wrote:
> 
>> Oh, and what is the content of register SCFG_SCFGREVCR?
> 
> Good point. On my board it's 0xffffffff, set even before U-boot starts,
> and lots board support code in U-boot expects this. I can't immediately
> find examples in the linux source code that actually writes to the scfg,

Not a write, but we do already implicitly assume SCFG_SCFGREVCR is set
to all-ones: In drivers/pci/dwc/pci-layerscape.c, bits which are
numbered 6-11 in the reference manual are extracted with a regmap_read()
followed by a left-shift by 20 and mask with 0x3f. That's consistent
with me setting bit 0 (reference manual enumeration) using 1U<<31.

Rasmus