linux-kernel - Re: [PATCH] clk: Register clkdev after setup of fixed-rate and fixed-factor clocks

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Date:   Sat, 12 Nov 2016 13:19:08 +0800
From:   Xiaolong Zhang <xiaolong.zhang@...eadtrum.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
CC:     <mturquette@...libre.com>, <orson.zhai@...eadtrum.com>,
        <baolin.wang@...eadtrum.com>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ben.li@...eadtrum.com>
Subject: Re: [PATCH] clk: Register clkdev after setup of fixed-rate and
 fixed-factor clocks

On 二, 10月 25, 2016 at 08:40:08下午 +0000, Stephen Boyd wrote:
> On 10/22, Xiaolong Zhang wrote:
> > On 四, 10月 20, 2016 at 04:01:03下午 -0700, Stephen Boyd wrote:
> > > On 10/11, Orson Zhai wrote:
> > > > From: Xiaolong Zhang <xiaolong.zhang@...eadtrum.com>
> > > > 
> > > > When common kernel setups fixed clock, of_clk_provider will be registerred.
> > > > But there is no clkdev being registerred at the same time. This will make
> > > > it difficult to get the clock by using clk_get(NULL, con_id).
> > > > 
> > > > Add clkdev register for fixed-rate and fixed-factor clock and ignore
> > > > the error if any.
> > > > 
> > > > Signed-off-by: Xiaolong Zhang <xiaolong.zhang@...eadtrum.com>
> > > > Signed-off-by: Orson Zhai <orson.zhai@...eadtrum.com>
> > > > ---
> > > 
> > > Why are we using clkdev lookups for clks populated from DT?
> > > Shouldn't we be able to point to them from the consumers that
> > > would also be in DT? I'm a little lost.
> > > 
> > The clk_get interface allows the first argument as NULL. We just assure
> > consumers can get the clock from DT or by clock name.
> 
> Ok. The first argument to clk_get() really shouldn't be NULL. It
> should be the device pointer for the device that is associated
> with the clk you want to get. The clock name (second argument to
> clk_get()) should be device specific and not some globally unique
> identifier. It seems that you're using the clk_get() API
> incorrectly.
>
Sorry for late reply.
There are two paths in clk_get:
a) dev is not NULL, the calling procedure is as following
clk_get(dev, con_id)
--->of_clk_get_by_name(dev->of_node, con_id)

b) dev is NULL, the calling procedure is as following
clk_dev(NULL, con_id)
--->clk_get_sys(NULL, con_id)
    --->clk_find(NULL, con_id)

I just cann't understand why you say the first argument shouldn't
be NULL. Is there other consideration in CCF?

Thanks

Xiaolong Zhang
> -- 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project