linux-kernel - Re: [PATCH v6 5/5] ARM: dts: sun9i: Initial support for the Sunchip CX-A99 board

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Message-ID: <20170214233538.enkffjiw3kkfromu@localhost>
Date:   Wed, 15 Feb 2017 00:35:39 +0100
From:   Rask Ingemann Lambertsen <rask@...melder.dk>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Lee Jones <lee.jones@...aro.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 5/5] ARM: dts: sun9i: Initial support for the Sunchip
 CX-A99 board

On Fri, Feb 10, 2017 at 05:22:21PM +0800, Chen-Yu Tsai wrote:
> On Fri, Feb 10, 2017 at 4:59 PM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
> > Hi,
> >
> > On Thu, Feb 09, 2017 at 12:34:06AM +0100, Rask Ingemann Lambertsen wrote:
[...]
> >> diff --git a/arch/arm/boot/dts/sun9i-a80-cx-a99.dts b/arch/arm/boot/dts/sun9i-a80-cx-a99.dts
> >> new file mode 100644
> >> index 0000000..f5496d2
> >> --- /dev/null
> >> +++ b/arch/arm/boot/dts/sun9i-a80-cx-a99.dts
[...]
> >> +     pmic@745 {
> >> +             compatible = "x-powers,axp808", "x-powers,axp806";
> 
> As you mentioned elsewhere, they are not really compatible.
> You should drop the latter compatible.

The compatibility is good enough that it works fine with the driver that
went into kernel 4.9 and 4.10. Using this device tree file, I have built and
booted 4.9.9 and 4.10-rc7 kernels as per the instructions here;
https://linux-sunxi.org/Sunchip_CX-A99#Linux_kernel
Likewise any other AXP806 driver which doesn't touch the register at address
0xff will work fine.

So, the disadvantage of removing the "x-powers,axp806" compatible is that
it breaks on two kernel versions where it works fine with the compatible.
What is the advantage of removing the "x-powers,axp806" compatible?

As to touching the register at 0xff, it would be interesting to know more
precisely what goes wrong. The symptom is these messages in the log:

[    3.209573] axp20x-rsb sunxi-rsb-745: AXP20x variant AXP806 found
[    3.210153] axp20x-rsb sunxi-rsb-745: Failed to set masks in 0x40: -5
[    3.210178] axp20x-rsb sunxi-rsb-745: failed to add irq chip: -5
[    3.210306] axp20x-rsb: probe of sunxi-rsb-745 failed with error -5

I haven't yet looked further into what happens at the RSB bus level.

-- 
Rask Ingemann Lambertsen