Messages in this thread |  | | Subject | Re: [PATCH v3] rtc: ac100: Fix ac100 determine rate bug | From | Philipp Rossak <> | Date | Sun, 18 Feb 2018 18:55:58 +0100 |
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On 16.02.2018 14:15, Chen-Yu Tsai wrote: > On Fri, Feb 16, 2018 at 9:07 PM, Maxime Ripard > <maxime.ripard@bootlin.com> wrote: >> On Fri, Feb 16, 2018 at 12:10:18PM +0800, Chen-Yu Tsai wrote: >>>> diff --git a/arch/arm/boot/dts/sun8i-a83t-bananapi-m3.dts >>>> b/arch/arm/boot/dts/sun8i-a83t-bananapi-m3.dts >>>> index 6550bf0e594b..6f56d429f17e 100644 >>>> --- a/arch/arm/boot/dts/sun8i-a83t-bananapi-m3.dts >>>> +++ b/arch/arm/boot/dts/sun8i-a83t-bananapi-m3.dts >>>> @@ -175,11 +175,18 @@ >>>> compatible = "x-powers,ac100-rtc"; >>>> interrupt-parent = <&r_intc>; >>>> interrupts = <0 IRQ_TYPE_LEVEL_LOW>; >>>> - clocks = <&ac100_codec>; >>>> + clocks = <&ac100_rtc_32k>; >>>> #clock-cells = <1>; >>>> clock-output-names = "cko1_rtc", >>>> "cko2_rtc", >>>> "cko3_rtc"; >>>> + >>>> + ac100_rtc_32k: rtc-32k-oscillator { >>>> + compatible = "fixed-clock"; >>>> + #clock-cells = <0>; >>>> + clock-frequency = <32768>; >>>> + clock-output-names = "ac100-rtc-32k"; >>>> + }; >>>> }; >>>> }; >>>> }; >>>> >>>> What do you think about that solution? >>> >>> That's not quite right either. As I mentioned before, the >>> RTC block has two clock inputs, one 4MHz signal from the >>> codec block, and one 32.768 kHz signal from an external >>> crystal. The original device tree binding describes the >>> first one, and the 32.768 kHz clock was registered by >>> the RTC driver internally. >>> >>> If you're going to add the crystal clock, you still need >>> to keep the codec one. Note that this does not fix what >>> Maxime is asking you. I've already provided an explanation: >>> >>> The clock core allows registering clocks with not-yet-existing >>> clock parents. Parents are matches by string names. If no >>> clock by that name is registered yet, the clock core simply >>> orphans the new clock if the unregistered parent is its >>> current parent or simply ignores that parent if its not the >>> current parent. This is entirely valid and is what we are >>> counting on here, as we haven't implemented the codec-side >>> driver. >> >> So, we end up in a situation where clk_hw_get_num_parents returns the >> amount of clocks we can be parented to (orphans or not), but >> clk_hw_get_parent_by_index will not return the orphan clocks? > > There is no placeholder for missing parents, unlike the regulator > subsystem that has a dummy regulator for this purpose. > >> That's pretty bad :/ > > Yeah. I didn't expect this to happen. But to be fair, I should > have done the check on clk_hw_get_parent_by_index. > >> Is there a way to test before registering that all our parents are >> actually there? clk_get? > > That's probably the way to do it. However in the AC100 RTC case, > I left it open to be missing on purpose, so we could use the RTC > without waiting for the codec to be supported. > > ChenYu >
So how should we proceed with this issue?
Should I send a new version with a fixed comment or should I implement the check in clk_get function?
For the second option I will need about 3 weeks to submit a proper patch since I have the next two weeks some other stuff to do. If a proper fix is required earlier, it might be better if someone else is taking care about a fix.
Philipp
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