Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk selection

[Grygorii Strashko]

On 11/30/2016 11:35 AM, Grygorii Strashko wrote:
>
>
> On 11/30/2016 03:56 AM, Richard Cochran wrote:
>> On Mon, Nov 28, 2016 at 05:04:24PM -0600, Grygorii Strashko wrote:
>>> Some CPTS instances, which can be found on KeyStone 2 1/10G Ethernet
>>> Switch Subsystems, can control an external multiplexer that selects
>>> one of up to 32 clocks for time sync reference (RFTCLK). This feature
>>> can be configured through CPTS_RFTCLK_SEL register (offset: x08).
>>>
>>> Hence, introduce optional DT cpts_rftclk_sel poperty wich, if present,
>>> will specify CPTS reference clock. The cpts_rftclk_sel should be
>>> omitted in DT if HW doesn't support this feature. The external fixed
>>> rate clocks can be defined in board files as "fixed-clock".
>>
>> Can't you implement this using the clock tree, rather than an ad-hoc
>> DT property?
>>
>
> I've thought about this, but decided to move forward with this impl
>  which is pretty simple. I will try.
>
>

I come with below RFC patch. if no objection I'll move forward with it.

According to Keystone 2 66AK2e DM there are 7 possible ref clocks:
0000 = SYSCLK2
0001 = SYSCLK3
0010 = TIMI0
0011 = TIMI1
0100 = TSIPCLKA
1000 = TSREFCLK
1100 = TSIPCLKB
Others = Reserved

2 from above clocks are internal SYSCLK2 and SYSCLK3 - other external
(board specific). So default definition of cpts_mux will have only two parents.
If ext clock is going to be use as cpts rftclk then it should be
defined in board file and  cpts_refclk_mux definition updated to support 
this ext clock:

timi1clk: timi1clk {
	#clock-cells = <0>;
	compatible = "fixed-clock";
	clock-frequency = <xxxxxxxxxx>;
	clock-output-names = "timi1";
};

&cpts_mux {
	clocks = <&chipclk12>, <&chipclk13>, <timi1clk>;
	cpts-mux-tbl = <0>, <1>, <3>;
	assigned-clocks = <&cpts_mux>;
	assigned-clock-parents = <&timi1clk>;
};