linux-kernel - Re: [PATCH v4 1/5] mfd: omap-usb-host: Update DT clock binding information

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Date:	Wed, 8 Jan 2014 15:57:19 +0530
From:	Roger Quadros <rogerq@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<bcousson@...libre.com>, <tony@...mide.com>, <balbi@...com>,
	<linux-omap@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	"Kristo, Tero" <t-kristo@...com>
Subject: Re: [PATCH v4 1/5] mfd: omap-usb-host: Update DT clock binding information

On 01/08/2014 03:49 PM, Arnd Bergmann wrote:
> On Wednesday 08 January 2014 15:39:36 Roger Quadros wrote:
>>> What about the other clocks acquired in drivers/mfd/omap-usb-host.c? Shouldn't
>>> all of those be provided by via the DT phandle?
>>>
>>
>> All those clocks are identically named across the OMAP SoCs and are unique for each
>> SoC, so providing DT phandle for all of them is not required.
>>
>> The init_60m_fclk was renamed to l3init_60m_fclk in OMAP5, and hence the need for
>> this binding.
> 
> What do you mean it was renamed? Is it a different version of the omap-usb-host
> device then?

I meant the clock gates name on the SoC was renamed. The omap-usb-host device version
is revised as well.

>>> Should the clk_get be changed to of_clk_get()/of_clk_get_by_name() in the
>>> driver? This would potentially remove the need of the init_60m_fclk name.
>>>
>>
>> If we use of_clk_xxx() then we'll need to update DT nodes for OMAP4 and OMAP3 as
>> well to explicitly provide the clock phandle. For now we make use of the fact that
>> SoC clock data names the clock rightly i.e. "init_60m_fclk".
> 
> I'm getting the feeling that init_60m_fclk is not the name of the clock input
> of the omap-usb-host device at all, but rather the name of a signal on the
> omap soc, which would not be an appropriate identifier for the binding.

It is a clock gate defined like so in the DT clock data

on OMAP4
        init_60m_fclk: init_60m_fclk {
                #clock-cells = <0>;
                compatible = "ti,divider-clock";
                clocks = <&dpll_usb_m2_ck>;
                reg = <0x0104>;
                ti,dividers = <1>, <8>;
        };

on OMAP5
        l3init_60m_fclk: l3init_60m_fclk {
                #clock-cells = <0>;
                compatible = "ti,divider-clock";
                clocks = <&dpll_usb_m2_ck>;
                reg = <0x0104>;
                ti,dividers = <1>, <8>;
        };

So you can see that it is the same thing with a different name.

cheers,
-roger
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