Messages in this thread | | | Date | Tue, 12 Jul 2022 15:03:39 +0200 | Subject | Re: [PATCH v1 08/16] arm64: dts: mt8195: Add power domains controller | From | AngeloGioacchino Del Regno <> |
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Il 12/07/22 14:58, Krzysztof Kozlowski ha scritto: > On 12/07/2022 14:54, AngeloGioacchino Del Regno wrote: >> Il 12/07/22 14:47, Krzysztof Kozlowski ha scritto: >>> On 12/07/2022 12:33, AngeloGioacchino Del Regno wrote: >>>> Il 12/07/22 11:03, Krzysztof Kozlowski ha scritto: >>>>> On 12/07/2022 10:53, AngeloGioacchino Del Regno wrote: >>>>>> Il 12/07/22 10:37, Krzysztof Kozlowski ha scritto: >>>>>>> On 12/07/2022 10:17, AngeloGioacchino Del Regno wrote: >>>>>>>> Il 06/07/22 17:18, Krzysztof Kozlowski ha scritto: >>>>>>>>> On 06/07/2022 14:00, Tinghan Shen wrote: >>>>>>>>>> Hi Krzysztof, >>>>>>>>>> >>>>>>>>>> After discussing your message with our power team, >>>>>>>>>> we realized that we need your help to ensure we fully understand you. >>>>>>>>>> >>>>>>>>>> On Mon, 2022-07-04 at 14:38 +0200, Krzysztof Kozlowski wrote: >>>>>>>>>>> On 04/07/2022 12:00, Tinghan Shen wrote: >>>>>>>>>>>> Add power domains controller node for mt8195. >>>>>>>>>>>> >>>>>>>>>>>> Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com> >>>>>>>>>>>> Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com> >>>>>>>>>>>> --- >>>>>>>>>>>> arch/arm64/boot/dts/mediatek/mt8195.dtsi | 327 +++++++++++++++++++++++ >>>>>>>>>>>> 1 file changed, 327 insertions(+) >>>>>>>>>>>> >>>>>>>>>>>> diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>>>>>>>>>>> index 8d59a7da3271..d52e140d9271 100644 >>>>>>>>>>>> --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>>>>>>>>>>> +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>>>>>>>>>>> @@ -10,6 +10,7 @@ >>>>>>>>>>>> #include <dt-bindings/interrupt-controller/irq.h> >>>>>>>>>>>> #include <dt-bindings/phy/phy.h> >>>>>>>>>>>> #include <dt-bindings/pinctrl/mt8195-pinfunc.h> >>>>>>>>>>>> +#include <dt-bindings/power/mt8195-power.h> >>>>>>>>>>>> >>>>>>>>>>>> / { >>>>>>>>>>>> compatible = "mediatek,mt8195"; >>>>>>>>>>>> @@ -338,6 +339,332 @@ >>>>>>>>>>>> #interrupt-cells = <2>; >>>>>>>>>>>> }; >>>>>>>>>>>> >>>>>>>>>>>> + scpsys: syscon@10006000 { >>>>>>>>>>>> + compatible = "syscon", "simple-mfd"; >>>>>>>>>>> >>>>>>>>>>> These compatibles cannot be alone. >>>>>>>>>> >>>>>>>>>> the scpsys sub node has the compatible of the power domain driver. >>>>>>>>>> do you suggest that the compatible in the sub node should move to here? >>>>>>>>> >>>>>>>>> Not necessarily, depends. You have here device node representing system >>>>>>>>> registers. They need they own compatibles, just like everywhere in the >>>>>>>>> kernel (except the broken cases...). >>>>>>>>> >>>>>>>>> Whether this should be compatible of power-domain driver, it depends >>>>>>>>> what this device node is. I don't know, I don't have your datasheets or >>>>>>>>> your architecture diagrams... >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>> + reg = <0 0x10006000 0 0x1000>; >>>>>>>>>>>> + #power-domain-cells = <1>; >>>>>>>>>>> >>>>>>>>>>> If it is simple MFD, then probably it is not a power domain provider. >>>>>>>>>>> Decide. >>>>>>>>>> >>>>>>>>>> this MFD device is the power controller on mt8195. >>>>>>>>> >>>>>>>>> Then it is not a simple MFD but a power controller. Do not use >>>>>>>>> "simple-mfd" compatible. >>>>>>>>> >>>>>>>>>> Some features need >>>>>>>>>> to do some operations on registers in this node. We think that implement >>>>>>>>>> the operation of these registers as the MFD device can provide flexibility >>>>>>>>>> for future use. We want to clarify if you're saying that an MFD device >>>>>>>>>> cannot be a power domain provider. >>>>>>>>> >>>>>>>>> MFD device is Linuxism, so it has nothing to do here. I am talking only >>>>>>>>> about simple-mfd. simple-mfd is a simple device only instantiating >>>>>>>>> children and not providing anything to anyone. Neither to children. This >>>>>>>>> the most important part. The children do not depend on anything from >>>>>>>>> simple-mfd device. For example simple-mfd device can be shut down >>>>>>>>> (gated) and children should still operate. Being a power domain >>>>>>>>> controller, contradicts this usually. >>>>>>>>> >>>>>>>> >>>>>>>> If my interpretation of this issue is right, I have pushed a solution for it. >>>>>>>> Krzysztof, Matthias, can you please check [1] and give feedback, so that >>>>>>>> Tinghan can rewrite this commit ASAP? >>>>>>>> >>>>>>>> Reason is - I need the MT8195 devicetree to be complete to push the remaining >>>>>>>> pieces for Tomato Chromebooks, of course. >>>>>>>> >>>>>>>> [1]: https://patchwork.kernel.org/project/linux-mediatek/list/?series=658527 >>>>>>> >>>>>>> I have two or three similar discussions, so maybe I lost the context, >>>>>>> but I don't understand how your fix is matching real hardware. >>>>>>> >>>>>>> In the patchset here, Tinghan claimed that power domain controller is a >>>>>>> child of 10006000. 10006000 is also a power domain controller. This was >>>>>>> explicitly described by the DTS code. >>>>>>> >>>>>>> Now you abandon this hierarchy in favor of syscon. If the hierarchy was >>>>>>> correct, your patchset does not match the hardware, so it's a no-go. >>>>>>> Describe the hardware. >>>>>>> >>>>>>> However maybe this patch did not make any sense and there is no >>>>>>> relationship parent-child... so what do you guys send here? Bunch of >>>>>>> hacks and work-arounds? >>>>>>> >>>>>> >>>>>> For how I get it, hardware side, the SPM (System Power Manager) resides inside >>>>>> of the SCPSYS block (consequently, in that iospace). >>>>>> >>>>>> As Matthias pointed out earlier, SCPSYS provides more functionality, but the >>>>>> only one that's currently implemented upstream is the System Power Manager, >>>>>> responsible for managing the MTCMOS (power domains). >>>>>> >>>>>> In any case, now I'm a little confused on how to proceed, can you please give >>>>>> some suggestion? >>>>> >>>>> You should make SCPSYS (0x10006000, AFAIU) a proper driver with its own >>>>> compatible (followed by syscon if needed), even if now it is almost >>>>> empty stub. The driver should populate OF children and then you can >>>>> embed SPM inside and reference to parent's regmap. No need for >>>>> simple-mfd. Later the SCPSYS can grow, if you ever need it. >>>>> >>>>> >>>> >>>> I see an issue with such approach: the SCPSYS doesn't have a mailbox, doesn't >>>> need power management from the Linux side, doesn't have any register to check >>>> HW revision, it's always online (hence it doesn't need Linux to boot it), it >>>> doesn't need any root clock, nor regulator, nor mmu context, and there's no >>>> retrievable "boot log" of any sort. >>> >>> No problems, there are other drivers who do not need any resources, >>> except address space. >>> >>>> >>>> Hence, a driver with its own compatible would be an empty stub forever: it's >>>> not going to get any "scpsys root handling" at all, because there's none to do. >>> >>> But it is a power domain provider, so you need to embed it in some >>> dirver, don't you? >>> >>> >>>> Digging through some downstream kernels, the only other functionality that I >>>> can find in the SCPSYS is a MODULE_RESET (which is used to reset the SCP System) >>>> and a INFRA_IRQ_SET, used to set "wake locks" on the AP and CONNSYS (modem). >>> >>> So why was power domain provider added to SCPSYS? Guys, I don't know >>> your architecture, so I deduct it based on pieces of DTS code I see. >>> >>>> >>>> Both of these may only be used in the SCP mailbox driver (which is *not* SCPSYS) >>>> to perform an ipi_send operation (but currently we simply en/disable the clock >>>> and that's enough), or to perform a reset and firmware reload of the SCP (but >>>> currently we're simply powering off and back on: this may change in the future). >>>> >>>> So, at the end of the day, we would end up having a copy of simple-pm-bus and >>>> nothing else, which doesn't look like being optimal at all. >>> >>> No, because you need that power domain driver, don't you? If you don't >>> need power domain provider/driver, why the heck this is there: >>> >>> + scpsys: syscon@10006000 { >>> + compatible = "syscon", "simple-mfd"; >>> + reg = <0 0x10006000 0 0x1000>; >>> + #power-domain-cells = <1>; >>> ^^^^^^^^^^^^^^^^^ >>> Entire discussion started from this. >>> >> >> Is this all a huge misunderstanding? It probably is, at least partially. >> >> That node shouldn't have any #power-domain-cells, the only PD is the SPM node >> (mediatek,mt8195-power-controller), not the scpsys parent! Ugh... > > My comment was quite clear I think: > > > + #power-domain-cells = <1>; > If it is simple MFD, then probably it is not a power domain provider. > Decide.
Yes it was quite clear. It's entirely my fault for misreading that part and I'm truly sorry for that.
> > and you keep telling me that it is a power domain provider and MFD and > something more. > > Anyway neither syscon nor simple-mfd can be without specific compatible. >
I believe, at this point, that adding a compatible like "mediatek,scpsys" in mfd/syscon.yaml should do?
> Best regards, > Krzysztof
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