linux-kernel - Re: [PATCH 0/4] clk: mvebu: fix clk init order

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Date:	Mon, 17 Feb 2014 16:28:41 +0100
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
CC:	Jason Cooper <jason@...edaemon.net>,
	Emilio López <emilio@...pez.com.ar>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Mike Turquette <mturquette@...aro.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/4] clk: mvebu: fix clk init order

On 17/02/2014 16:21, Ezequiel Garcia wrote:
> On Mon, Feb 17, 2014 at 03:25:22PM +0100, Gregory CLEMENT wrote:
>> On 17/02/2014 15:13, Ezequiel Garcia wrote:
>>> On Wed, Feb 05, 2014 at 01:34:57PM -0500, Jason Cooper wrote:
>>>> On Sat, Jan 25, 2014 at 07:19:06PM +0100, Sebastian Hesselbarth wrote:
>>>>> This patch set fixes clk init order that went upside-down with
>>>>> v3.14. I haven't really investigated what caused this, but I assume
>>>>> it is related with DT node reordering by addresses.
>>>>>
>>>>> Anyway, with v3.14 for MVEBU SoCs, the clock gating driver gets
>>>>> registered before core clocks driver. Unfortunately, we cannot
>>>>> return -EPROBE_DEFER in drivers initialized by clk_of_init. As the
>>>>> init order for our drivers is always core clocks before clock gating,
>>>>> we maintain init order ourselves by hooking CLK_OF_DECLARE to one
>>>>> init function that will register core clocks before clock gating
>>>>> driver.
>>>>>
>>>>> This patch is based on pre-v3.14-rc1 mainline and should go in as
>>>>> fixes for it. As we now send MVEBU clk pull-requests to Mike directly,
>>>>> I suggest Jason picks it up as a topic branch.
>>>>>
>>>>> The patches have been boot tested on Dove and compile-tested only
>>>>> for Kirkwood, Armada 370 and XP.
>>>>>
>>>>> Sebastian Hesselbarth (4):
>>>>>   clk: mvebu: armada-370: maintain clock init order
>>>>>   clk: mvebu: armada-xp: maintain clock init order
>>>>>   clk: mvebu: dove: maintain clock init order
>>>>>   clk: mvebu: kirkwood: maintain clock init order
>>>>>
>>>>>  drivers/clk/mvebu/armada-370.c | 21 ++++++++++-----------
>>>>>  drivers/clk/mvebu/armada-xp.c  | 20 +++++++++-----------
>>>>>  drivers/clk/mvebu/dove.c       | 19 +++++++++----------
>>>>>  drivers/clk/mvebu/kirkwood.c   | 34 ++++++++++++++++------------------
>>>>>  4 files changed, 44 insertions(+), 50 deletions(-)
>>>>
>>>> Whole series applied to mvebu/clk-fixes.
>>>>
>>>
>>> Are we still in time to consider Emilio's oneline proposal?
>>> (Emilio: would you mind preparing a suitable patch against dove,
>>> kirkwood, armada370/xp, so we can see the real thing?).
>>
>> I am still strongly against this proposal because hard-coded the parent
>> clock name in the driver seems very wrong and moreover in some circumstances
>> (if there is no output-name, which is our default case) this proposal
>> just ignored the parent clock given by the device tree and this looked
>> more wrong.
>>
> 
> So you're against the proposal as a permanent fix, *and* against the
> proposal as a workaround fix?

Yes

> 
>>>
>>> Sebastian fix works perfect, and it easy to understand. However, it has
>>> quite a large diffstat. When compared to Emilio's oneline proposal, it
>>> seems to me it would be preferable, unless it's broken.
>>>
>>> Workaround or not, the fact is this code will be in v3.14, so maybe we
>>> can spend some time considering a cleaner option.
>>>
> 
> Before discussing the solution as compared to your for-v3.15 clock
> registration order patch, I wanted to trigger some discussion around
> replacing this big and intrusive workaround with Emilio's oneline fix.
> 
> Let's suppose we're considering them as workaround to live just one or
> two releases. Wouldn't it be better to take the least instrusive?
> 

The better solution is the one which doesn't add another regression and until
today I though we had an agreement to use the patch set from Sebastian. If
I remember well Jason had sent a pull request for it.


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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