From mboxrd@z Thu Jan  1 00:00:00 1970
From: sebastian.hesselbarth@gmail.com (Sebastian Hesselbarth)
Date: Mon, 19 Aug 2013 01:33:18 +0200
Subject: [PATCH v4 5/6] clocksource: armada-370-xp: Fix device-tree binding
In-Reply-To: <20130817164319.GA2772@localhost>
References: <1376404995-24548-1-git-send-email-ezequiel.garcia@free-electrons.com>
 <20130815162751.GA2403@localhost> <520EB5BC.4060102@wwwdotorg.org>
 <1982398.OuHBuuDmYS@flatron> <520F6CA8.1090401@gmail.com>
 <20130817164319.GA2772@localhost>
Message-ID: <521159BE.1020206@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 08/17/2013 06:43 PM, Ezequiel Garcia wrote:
> On Sat, Aug 17, 2013 at 02:29:28PM +0200, Sebastian Hesselbarth wrote:
>
> In fact: I'm not sure. I'm slightly inclined towards considering both
> clocks as clock sources, just as Stephen and Tomasz are proposing.
>
>> But in the end, passing it by DT should be the way to go. I cannot look
>> into the XP datasheet, but I would guess that the exact feature of the
>> ip is not to use _the_ fixed 25MHz clock but XTAL as reference. Maybe
>> one of the free-electrons guys can look it up?
>>
>
> No, the documentation has a register bit for "25Mhz frequency enable",
> for each timer/watchdog.
>
> ---
>
> Anyway, I (almost) agree that the 25Mhz fixed clock must be somehow represented
> in the device-tree, but I'm not exactly sure how. Gregory: maybe you can help
> in this?
>

In armada-370-xp.dtsi add a 25MHz ref clock node and modify timer node
to reference it:

cpus { ... };

clocks {
	ref25M: timer-clock {
		compatible = "fixed-clock";
		clock-frequency = <25000000>;
	};
}

...

internal-regs {
	timer at 20300 {
		compatible = "marvell,armada-370-xp-timer";
		reg = <0x20300 0x30>, <0x21040 0x30>;
		interrupts = <37>, <38>, <39>, <40>, <5>, <6>;
		clocks = <&coreclk 2>, <&ref25M>;
		clock-names = "fabric", "fixed";
	};
};

Then use of_clk_get_by_name(np, "fabric") and of_clk_get_by_name(np,
"fixed") respectively. Clock select strategy should be, (a) fail if
no clock, (b) use fabric/fixed if just one clock, (c) use fixed if
both clocks.

Does that answer your questions? :)

Sebastian