Re: [PATCH v3 3/6] dt-bindings: devfreq: Add bindings for imx ddr controller

From: Rob Herring <robh@kernel.org>
To: Leonard Crestez <leonard.crestez@nxp.com>
Cc: "MyungJoo Ham" <myungjoo.ham@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Chanwoo Choi" <cw00.choi@samsung.com>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Michael Turquette" <mturquette@baylibre.com>,
	"Artur Świgoń" <a.swigon@partner.samsung.com>,
	"Saravana Kannan" <saravanak@google.com>,
	"Angus Ainslie" <angus@akkea.ca>,
	"Martin Kepplinger" <martink@posteo.de>,
	"Matthias Kaehlcke" <mka@chromium.org>,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Alexandre Bailon" <abailon@baylibre.com>,
	"Georgi Djakov" <georgi.djakov@linaro.org>,
	"Aisheng Dong" <aisheng.dong@nxp.com>,
	"Abel Vesa" <abel.vesa@nxp.com>, "Jacky Bai" <ping.bai@nxp.com>,
	"Anson Huang" <anson.huang@nxp.com>,
	"Fabio Estevam" <fabio.estevam@nxp.com>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
	dl-linux-imx <linux-imx@nxp.com>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 3/6] dt-bindings: devfreq: Add bindings for imx ddr controller
Date: Tue, 5 Nov 2019 14:13:02 -0600	[thread overview]
Message-ID: <20191105201302.GA4772@bogus> (raw)
In-Reply-To: <VI1PR04MB7023F375AEDC4549FA12247FEE7E0@VI1PR04MB7023.eurprd04.prod.outlook.com>

On Tue, Nov 05, 2019 at 07:25:57PM +0000, Leonard Crestez wrote:
> On 05.11.2019 00:21, Rob Herring wrote:
> > On Thu, Oct 31, 2019 at 11:50:24PM +0200, Leonard Crestez wrote:
> >> Add devicetree bindings for the i.MX DDR Controller on imx8m series
> >> chips. It supports dynamic frequency switching between multiple data
> >> rates and this is exposed to Linux via the devfreq subsystem.
> >>
> >> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> >> ---
> >>   .../devicetree/bindings/devfreq/imx-ddrc.yaml | 60 +++++++++++++++++++
> > 
> > .../bindings/memory-controllers/
> 
> Okay, but I'm not sure about the rules here. Usually there is a 1:1 
> mapping between subsystems and bindings directory but I guess devfreq is 
> odd since it's not really a physical class of device.

Mostly true, but it's not completely 1:1.

> I saw there is also a drivers/memory and there is already a 
> devfreq-using driver in there (EXYNOS5422_DMC).

Yeah, well it's been a while since I last tried to clean up locations of 
things. DDR controller bindings are not in the best shape.

> It's not clear if my driver fits in there; as far as I can see the only 
> "core" functionality in drivers/memory is parsing DDR timings from DTS 
> but for imx8m this is all controlled in firmware.

You shouldn't have to think about that. Bindings should be for DDR 
controllers regardless of whether there's a driver for devfreq, EDAC, 
perf, or ??? or all of those.

Rob