Date: Wed, 18 Feb 2015 11:58:53 +0000
From: Lee Jones <lee.jones@linaro.org>
To: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Antoine Tenart <antoine.tenart@free-electrons.com>, sameo@linux.intel.com,
        jszhang@marvell.com, zmxu@marvell.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        arnd@arndb.de
Subject: Re: [PATCH 01/11] mfd: add the Berlin controller driver
Message-ID: <20150218115853.GB22296@x1>
References: <1423671332-24580-1-git-send-email-antoine.tenart@free-electrons.com>
 <1423671332-24580-2-git-send-email-antoine.tenart@free-electrons.com>
 <20150216124808.GC14545@x1>
 <20150217092020.GC4507@kwain>
 <20150217115447.GA3989@x1>
 <20150218084004.GD21937@kwain>
 <20150218090958.GA18042@x1>
 <20150218092225.GE21937@kwain>
 <20150218104023.GA22296@x1>
 <54E4730D.1060507@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <54E4730D.1060507@gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2586
Lines: 66

On Wed, 18 Feb 2015, Sebastian Hesselbarth wrote:

> On 18.02.2015 11:40, Lee Jones wrote:
> >On Wed, 18 Feb 2015, Antoine Tenart wrote:
> [...]
> >>chip: chip-controller@ea0000 {
> >>         compatible = "marvell,berlin2q-chip-ctrl", "syscon";
> >>         reg = <0xea0000 0x400>, <0xdd0170 0x10>;
> >>         #clock-cells = <1>;
> >>         clocks = <&refclk>;
> >>         clock-names = "refclk";
> >>
> >>         soc_pinctrl: pin-controller {
> >>                 compatible = "marvell,berlin2q-soc-pinctrl";
> >>
> >>                 twsi0_pmux: twsi0-pmux {
> >>                         groups = "G6";
> >>                         function = "twsi0";
> >>                 };
> >>
> >>                 twsi1_pmux: twsi1-pmux {
> >>                         groups = "G7";
> >>                         function = "twsi1";
> >>                 };
> >>         };
> >>
> >>         chip_rst: reset {
> >>                 compatible = "marvell,berlin2-reset";
> >>                 #reset-cells = <2>;
> >>         };
> >>};
> >
> >This is what I'd expect to see in DT, so we're heading in the right
> >direction.  So make to my original question, what's the point of this
> >MFD driver, and why don't you just let DT framework register these
> >devices for you?
> >
> >You issue a compatible string here, then duplicate it in the driver,
> >why do you think this is necessary?
> 
> there is no DT framework that automatically probes for
> compatible<->driver matches. You either make it "simple-bus" compatible
> which will call of_foo_populate() or you have to register each of the
> devices yourself. It clearly is not a bus, so if we use this as a
> workaround, we'll get yelled at by others.

I do agree that using 'simple-bus' to describe only this IP would be
an abuse.  However, my foundation thought/argument is unchanged.  This
'driver' is a hack.  It has no functional use besides to work around a
problem of semantics and as such has no place in MFD.

Back onto the simple-bus theme, as this is a syscon device it is a bus
of sorts.  Have you thought about making it a child of your its syscon
node, then using simple-bus to get the OF framework to register the
child devices?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/