From mboxrd@z Thu Jan  1 00:00:00 1970
From: sebastian.hesselbarth@gmail.com (Sebastian Hesselbarth)
Date: Sat, 17 Aug 2013 14:29:28 +0200
Subject: [PATCH v4 5/6] clocksource: armada-370-xp: Fix device-tree binding
In-Reply-To: <1982398.OuHBuuDmYS@flatron>
References: <1376404995-24548-1-git-send-email-ezequiel.garcia@free-electrons.com>
 <20130815162751.GA2403@localhost> <520EB5BC.4060102@wwwdotorg.org>
 <1982398.OuHBuuDmYS@flatron>
Message-ID: <520F6CA8.1090401@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 08/17/2013 02:09 PM, Tomasz Figa wrote:
> On Friday 16 of August 2013 17:29:00 Stephen Warren wrote:
>> On 08/15/2013 10:27 AM, Ezequiel Garcia wrote:
>> ...
>>
>>> Armada XP
>>> ---------
>>>
>>> Two clock sources are available for timer and watchdog counters:
>>>
>>> Just as explained for the Armada 370, the timer and watchdog counters
>>> decrement rate is a configurable ratio of the L2/coherency fabric
>>> clock. The current clocksource driver implementation chooses an
>>> abritrary ratio.
>>>
>>> In addition to this, both timer and watchdog counter rate can be
>>> configured to use an (internal) 25 MHz fixed clock.
>>
>> So there are clearly two clocks fed into the HW block here. The DT
>> should reflect that.
>
> I fully agree. DT should list all the input clocks that are fed into the
> IP block being described.

I don't object to the above, but strictly speaking the consequence
would be, that all nodes require a clocks property. For A370/XP timer
the fabric clock is configurable and needs to be passed among core
clocks and timer, the 25MHz clock is not and _could_ be seen as an extra
feature of the core.

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?

Sebastian