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
Date: Wed, 18 Feb 2015 15:06:02 +0000 [thread overview]
Message-ID: <20150218150602.GE22296@x1> (raw)
In-Reply-To: <54E48EF0.4050807@gmail.com>
On Wed, 18 Feb 2015, Sebastian Hesselbarth wrote:
> On 02/18/2015 12:58 PM, Lee Jones wrote:
> >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.
>
> Lee,
>
> sorry I don't get it. Here you say that using simple-bus is an abuse...
>
> >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?
>
> ... and here you suggest to use simple-bus to register the child
> devices?
Nope, that's not what I said:
"I do agree that using 'simple-bus' to describe *ONLY THIS IP* would
be an abuse."
... although I believe there is a need to treat syscon devices as
simple buses. There are examples of devices doing this already:
git grep -El 'syscon.*simple-bus' next/master
next/master:arch/arm/boot/dts/imx6qdl.dtsi
next/master:arch/arm/boot/dts/imx6sl.dtsi
next/master:arch/arm/boot/dts/imx6sx.dtsi
next/master:arch/arm/boot/dts/zynq-7000.dtsi
> I fundamentally disagree that either this registers or syscon in general
> should in any way be seen as a bus. The chip control registers is an
> highly unsorted bunch of bits that we try to match with cleanly
> separated subsystems. This makes it a resource but no bus of any sort.
This is where my comment about semantics comes into play. syscon may
not be a bus is the truest sense; however, this is clearly a
requirement for sub devices to be probed in the same way a simple-bus
is currently. So we're just missing a framework somewhere. We can
fix that.
> The problem that we try to solve here is not a DT problem but solely
> driven by the fact that we need something to register platform_devices
> for pinctrl and reset. The unit we describe in DT is a pinctrl-clock-
> power-reset-unit - or short chip control.
I agree with the last part, but this is a DT problem. It lacks the
functionality to be able to cleanly register these types of
(sub-)devices. Devices which, in my opinion should be described
inside the parent syscon node.
> If you argue that mfd is not the right place for this "driver" we'll
> have to find a different place for it. I remember Mike has no problem
> with extending early probed clock drivers to register additional
> platform_devices - so I guess we end up putting it in there ignoring
> mfd's ability to do it for us.
My argument is not that this fake driver doesn't belong in MFD, it's
that it doesn't belong. That includes shoving it in drivers/clk. I
will be only too happy to have a chat with Mike and provide him with
my reasons why.
What I think we should do however, it write some framework code which
can neatly handle these use-cases, which may just be a case of:
s/of_platform_bus_probe/of_platform_subdevice_probe/
... obviously I'm oversimplifying by quite some margin, but I'm sure
you catch my drift.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2015-02-18 15:06 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-11 16:15 [PATCH 00/11] ARM: berlin: refactor chip and system controllers Antoine Tenart
2015-02-11 16:15 ` [PATCH 01/11] mfd: add the Berlin controller driver Antoine Tenart
2015-02-16 12:48 ` Lee Jones
2015-02-17 9:20 ` Antoine Tenart
2015-02-17 11:54 ` Lee Jones
2015-02-18 8:40 ` Antoine Tenart
2015-02-18 9:09 ` Lee Jones
2015-02-18 9:22 ` Antoine Tenart
2015-02-18 10:40 ` Lee Jones
2015-02-18 10:51 ` Antoine Tenart
2015-02-18 11:10 ` Sebastian Hesselbarth
2015-02-18 11:58 ` Lee Jones
2015-02-18 13:09 ` Sebastian Hesselbarth
2015-02-18 15:06 ` Lee Jones [this message]
2015-02-18 15:07 ` Lee Jones
2015-02-18 15:06 ` Arnd Bergmann
2015-02-18 15:59 ` Sebastian Hesselbarth
2015-02-18 16:15 ` Arnd Bergmann
2015-02-18 16:26 ` Lee Jones
2015-02-18 10:27 ` Sebastian Hesselbarth
2015-02-11 16:15 ` [PATCH 02/11] Documentation: bindings: add the Berlin controller documentation Antoine Tenart
2015-02-11 16:15 ` [PATCH 03/11] ARM: berlin: select MFD_BERLIN_CTRL Antoine Tenart
2015-02-11 16:15 ` [PATCH 04/11] reset: berlin: convert to a platform driver Antoine Tenart
2015-02-11 16:15 ` [PATCH 05/11] Documentation: bindings: move the Berlin reset documentation Antoine Tenart
2015-02-11 16:15 ` [PATCH 06/11] pinctrl: berlin: use the regmap provided by syscon Antoine Tenart
2015-03-05 9:38 ` Linus Walleij
2015-02-11 16:15 ` [PATCH 07/11] pinctrl: berlin: use proper compatibles Antoine Tenart
2015-03-05 9:39 ` Linus Walleij
2015-02-11 16:15 ` [PATCH 08/11] Documentation: bindings: move the Berlin pinctrl documentation Antoine Tenart
2015-03-05 9:41 ` Linus Walleij
2015-02-11 16:15 ` [PATCH 09/11] ARM: berlin: rework chip and system controller nodes for BG2 Antoine Tenart
2015-02-18 10:29 ` Sebastian Hesselbarth
2015-02-18 10:33 ` Antoine Tenart
2015-02-18 10:35 ` Sebastian Hesselbarth
2015-02-11 16:15 ` [PATCH 10/11] ARM: berlin: rework chip and system controller nodes for BG2CD Antoine Tenart
2015-02-11 16:15 ` [PATCH 11/11] ARM: berlin: rework chip and system controller nodes for BG2Q Antoine Tenart
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