[rtc-linux] Re: [PATCH] rtc: sunxi: use external oscillator

[Stephan Roslen <stephan@roslen.de>]

On 07.07.2016 06:50, Stephan Roslen wrote:
> On 06.07.2016 22:20, Maxime Ripard wrote:
>> The issue is actually worse than that.
>>
>> That register controls the losc source for the whole clock tree, so it
>> will affect every clock in the system.
>>
>> In order to have that correctly propagated, you should register a new
>> mux here in the clock framework, and have all the other clocks using
>> that mux as a parent.
>=20
> I agree. Checking the diagram in subsection 1.5.2 of the A20 manual it se=
ems, that LOSC can be a source for clocks like CPU and some SoC busses. So =
my patch could indeed mess with the whole clock tree.

Sorry for the addition. The mess of course is not that huge, for the mux se=
lects between a 32KHz Oscillator with +- 20% tolerance, thus ranging from 2=
5.6 to 38.4 KHz and the 32.768KHz external oscillator. Hence muxing to 32.7=
68KHz should be no problem for any clk, that was fine with the internal osc=
illator as clk source. Though still you're absolutely right, that this shou=
ld be handled in code correctly.

Stephan

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