linux-kernel - Re: [PATCH v2 1/2] clk: Hi3660: change to register crgctrl clock with CLK_OF_DECLARE

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Message-ID: <20170518094853.GB25294@leoy-ThinkPad-T440>
Date:   Thu, 18 May 2017 17:48:54 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Wei Xu <xuwei5@...ilicon.com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Guodong Xu <guodong.xu@...aro.org>,
        Zhong Kaihua <zhongkaihua@...wei.com>,
        Chen Jun <chenjun14@...wei.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 1/2] clk: Hi3660: change to register crgctrl clock
 with CLK_OF_DECLARE_DRIVER

Hi Daniel,

On Thu, May 18, 2017 at 11:32:26AM +0200, Daniel Lezcano wrote:
> On Thu, May 18, 2017 at 09:50:46AM +0800, Leo Yan wrote:
> > The timer will register into system at very early phase at kernel boot;
> > if timer needs to use clock, the clock should be get ready in function
> > of_clk_init() so later the timer driver probe can retrieve clock
> > successfully. This is finished in below flow on arm64:
> > 
> >   start_kernel()
> >     `-> time_init()
> >           `-> of_clk_init(NULL)    => register timer's clock
> >           `-> clocksource_probe()  => register timer
> > 
> > On Hi3660 the sp804 timer uses clock "osc32k", this clock is registered
> > as platform driver rather than CLK_OF_DECLARE_DRIVER method. As result,
> > sp804 timer probe returns failure due if cannot bind clock properly.
> > To fix the failure, this patch is to change crgctrl clock registration
> > from platform driver to CLK_OF_DECLARE_DRIVER method so the clocks can
> > be registered ahead with function of_clk_init() and then timer driver
> > can use it.
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> >  drivers/clk/hisilicon/clk-hi3660.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/clk/hisilicon/clk-hi3660.c b/drivers/clk/hisilicon/clk-hi3660.c
> > index fd5ce7f..4e5713b 100644
> > --- a/drivers/clk/hisilicon/clk-hi3660.c
> > +++ b/drivers/clk/hisilicon/clk-hi3660.c
> > @@ -547,10 +547,10 @@ static void hi3660_clk_crgctrl_init(struct device_node *np)
> >  				  ARRAY_SIZE(hi3660_crgctrl_divider_clks),
> >  				  clk_data);
> >  }
> > +CLK_OF_DECLARE_DRIVER(hi3660_clk_crgctrl, "hisilicon,hi3660-crgctrl",
> > +		      hi3660_clk_crgctrl_init);
> >  
> >  static const struct of_device_id hi3660_clk_match_table[] = {
> > -	{ .compatible = "hisilicon,hi3660-crgctrl",
> > -	  .data = hi3660_clk_crgctrl_init },
> >  	{ .compatible = "hisilicon,hi3660-pctrl",
> >  	  .data = hi3660_clk_pctrl_init },
> >  	{ .compatible = "hisilicon,hi3660-pmuctrl",
> 
> Why not do the change for all the clocks and remove the
> hi3660_clk_match_table[]? and all the related platform driver code?
> 
> That will be consistent with the other clk-hi* drivers.

I checked a bit with Stephen on IRC, follow the suggestion to 'split
the clks are registsered between CLK_OF_DECLARE_DRIVER() and driver
probe so that the ones you need really early are done through the
CLK_OF path and the other ones are done through regular driver probe'.

Also checked for mainline kernel, now there have some examples,
like: drivers/clk/mediatek/clk-mt2701.c.

Thanks,
Leo Yan