-----Original Message-----
From: Wood Scott-B07421
Sent: Friday, August 29, 2014 12:26 AM
To: Lu Jingchang-B35083
Cc: mturquette at linaro.org; linuxppc-dev at lists.ozlabs.org; linux-
kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org
Subject: Re: [RESEND] clk: ppc-corenet: Add Freescale ARM-based platforms
CLK_OF_DECLARE support

On Thu, 2014-08-28 at 05:05 -0500, Lu Jingchang-B35083 wrote:

quoted

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Thursday, August 28, 2014 7:34 AM
To: Lu Jingchang-B35083
Cc: mturquette at linaro.org; linuxppc-dev at lists.ozlabs.org; linux-
kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org
Subject: Re: [RESEND] clk: ppc-corenet: Add Freescale ARM-based
platforms CLK_OF_DECLARE support

On Tue, 2014-08-26 at 21:19 -0500, Lu Jingchang-B35083 wrote:

quoted

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, August 27, 2014 6:51 AM
To: Lu Jingchang-B35083
Cc: mturquette at linaro.org; linuxppc-dev at lists.ozlabs.org; linux-
kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org
Subject: Re: [RESEND] clk: ppc-corenet: Add Freescale ARM-based
platforms CLK_OF_DECLARE support

On Fri, 2014-08-22 at 17:34 +0800, Jingchang Lu wrote:

quoted

+CLK_OF_DECLARE(ppc_core_pll_v1, "fsl,qoriq-core-pll-1.0",

core_pll_init);

quoted

+CLK_OF_DECLARE(ppc_core_pll_v2, "fsl,qoriq-core-pll-2.0",

core_pll_init);

quoted

+CLK_OF_DECLARE(ppc_core_mux_v1, "fsl,qoriq-core-mux-1.0",

core_mux_init);

quoted

+CLK_OF_DECLARE(ppc_core_mux_v2, "fsl,qoriq-core-mux-2.0",

core_mux_init);

What does this do that the existing platform driver and match
table don't?  Why is it needed for ARM when PPC didn't need it?

-Scott

Common clk init on ARM platform is initialized earlier via
of_clk_init() instead of driver probe method, the of_clk_init will
walk a __clk_of_table to init each clk provider in the table, the
CLK_OF_DECLARE() macro puts a supported clk in the __clk_of_table
for it

initializing on starup, and the clk system has added some common clk
such as "fixed-clk"

quoted

to this table already.
So here I add our specific clk init declaration to consist this
framework, and the driver probe function will not be needed on ARM.

OK... Is there any reason why the new method won't work on PPC?

PPC has little dependence on the clock tree but frequency, it will
work well if adopted I think.

I'm just saying it seems redundant to have both.  Even on ARM, won't this
result in the clock getting registered twice (albeit with one of those
times being too late)?

Regardless of what dependence PPC has on the clock tree, what stops this
method of enumeration from working on PPC?  Is there anything required
other than inserting a call to of_clk_init(NULL) in the arch init code?

-Scott

The of_clk_init is an alternative way to the legacy driver. 
Latest ARM standard support a default call to of_clk_init(NULL) in its time_init().
So this is the general way for ARM-based platform.
The clk register layer can detect the twice registration of a same clk and
avoid the duplicate registration. The dtb should select the compatible for either,
but not both. On LS1021A the driver probe method will not be triggered.
And for support of of_clk_init on PPC, I think just add a call to it as ARM do
in time_init()[arch/arm/kernel/time.c] would be ok.



Best Regards,
Jingchang