linux-kernel - Re: [PATCH v5 1/6] clk: hisilicon: add CRG driver for hi3519 soc

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Message-ID: <CAAObsKBbUaGi-ZWg+Y-OCq=xVOgBJroMTVsqP2JpVHPQWcM4=w@mail.gmail.com>
Date:	Wed, 20 Jan 2016 07:38:13 +0100
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Rob Herring <robh+dt@...nel.org>
Cc:	xuejiancheng <xuejiancheng@...wei.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Kevin Hilman <khilman@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Wei Xu <xuwei5@...ilicon.com>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Zhangfei Gao <zhangfei.gao@...aro.org>,
	Bintian Wang <bintian.wang@...wei.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-clk <linux-clk@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, yanhaifeng@...ilicon.com,
	yanghongwei@...ilicon.com, suwenping@...ilicon.com,
	ml.yang@...ilicon.com, gaofei@...ilicon.com,
	zhangzhenxing@...ilicon.com, xuejiancheng@...ilicon.com
Subject: Re: [PATCH v5 1/6] clk: hisilicon: add CRG driver for hi3519 soc

On 19 January 2016 at 19:20, Rob Herring <robh+dt@...nel.org> wrote:
> On Fri, Jan 15, 2016 at 1:57 AM, xuejiancheng <xuejiancheng@...wei.com> wrote:
>>
>> On 2016/1/14 21:16, xuejiancheng wrote:
>>> Hi Mike,
>>>
>>> On 2016/1/14 2:57, Michael Turquette wrote:
>>>> Quoting xuejiancheng (2016-01-12 19:03:01)
>>>>> Hi Stephen,
>>>>>    Thank you very much for your reply.
>>>>>
>>>>> On 2016/1/13 6:12, Stephen Boyd wrote:
>>>>>> On 01/08, Jiancheng Xue wrote:
>>>>>>> diff --git a/drivers/clk/hisilicon/Kconfig b/drivers/clk/hisilicon/Kconfig
>>>>>>> index e434854..b6baebf 100644
>>>>>>> --- a/drivers/clk/hisilicon/Kconfig
>>>>>>> +++ b/drivers/clk/hisilicon/Kconfig
>>>>>>> @@ -1,3 +1,10 @@
>>>>>>> +config COMMON_CLK_HI3519
>>>>>>> +    tristate "Clock Driver for Hi3519"
>>>>>>
>>>>>> It looks like this has to be bool. Otherwise it needs to be a
>>>>>> platform driver and the hisilicon APIs need to be exported and
>>>>>> lose their __init markings.
>>>>>>
>>>>> Yes,it's a problem. I will fix it in next version. Thank you.
>>>>
>>>> The best solution would be to make this clock driver a real platform
>>>> driver.
>>>>
>>> Now the work clock of the clocksource timer-sp804 is provided by this driver. So
>>> it need to be registered early by CLK_OF_DECLARE. If the timer clock is treated
>>> as a fixed-clock provider, this driver can be implemented as a platform driver.
>>> Then the crg device must be registered before other clock consumer devices.Accordingly
>>> the crg device node must be written above all other clock consumer devices node in dts files.
>>> I think it is also a dependence.
>>>
>>> Can you help me understand why it is better to make this driver a platform driver?
>>> Thank you very much!
>>>
>> arch_initcall(customize_machine)
>> -->of_platform_populate
>>    -->of_platform_bus_create
>>      -->of_amba_device_create
>>         -->amba_device_add
>>            -->amba_get_enable_pclk
>> The call sequence above shows that the clock of the amba device must be registered before
>> amba_device_add. The clock of "arm,pl011" uart is registered in the probe function of the
>> platform driver "hi3519-crg". So the platform device "hi3519-crg" must be created before
>> the amba device "arm,pl011" uart.
>
> It is a problem, but Tomeu had a fix to support deferred probes here.
> That was part of the on-demand probing series, but maybe it needs to
> be applied separately if we are moving clock drivers to platform
> drivers.

Hi,

Marek Szyprowski has kindly taken those two patches as part of a series of him:

http://lkml.kernel.org/g/1450868368-5650-1-git-send-email-m.szyprowski@samsung.com

I think it would be great if you could test them and report.

Thanks,

Tomeu