On 13/02/2025 12:14, Haylen Chu wrote: > On Tue, Feb 11, 2025 at 09:03:20AM +0100, Krzysztof Kozlowski wrote: >> On 11/02/2025 06:15, Haylen Chu wrote: >>> On Sat, Jan 04, 2025 at 11:07:58AM +0100, Krzysztof Kozlowski wrote: >>>> On Fri, Jan 03, 2025 at 09:56:35PM +0000, Haylen Chu wrote: >>>>> Add documentation to describe Spacemit K1 system controller registers. >>>>> >>>>> Signed-off-by: Haylen Chu <heylenay@xxxxxxx> >>>>> --- >>>>> .../soc/spacemit/spacemit,k1-syscon.yaml | 52 +++++++++++++++++++ >>>>> 1 file changed, 52 insertions(+) >>>>> create mode 100644 Documentation/devicetree/bindings/soc/spacemit/spacemit,k1-syscon.yaml >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/soc/spacemit/spacemit,k1-syscon.yaml b/Documentation/devicetree/bindings/soc/spacemit/spacemit,k1-syscon.yaml >>>>> new file mode 100644 >>>>> index 000000000000..79c4a74ff30e >>>>> --- /dev/null >>>>> +++ b/Documentation/devicetree/bindings/soc/spacemit/spacemit,k1-syscon.yaml >>>>> @@ -0,0 +1,52 @@ >>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >>>>> +%YAML 1.2 >>>>> +--- >>>>> +$id: http://devicetree.org/schemas/soc/spacemit/spacemit,k1-syscon.yaml# >>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml# >>>>> + >>>>> +title: Spacemit K1 SoC System Controller >>>>> + >>>>> +maintainers: >>>>> + - Haylen Chu <heylenay@xxxxxxx> >>>>> + >>>>> +description: >>>>> + The Spacemit K1 SoC system controller provides access to shared register files >>>>> + for related SoC modules, such as clock controller and reset controller. >>>>> + >>>>> +properties: >>>>> + compatible: >>>>> + items: >>>>> + - enum: >>>>> + - spacemit,k1-apbc-syscon >>>>> + - spacemit,k1-apbs-syscon >>>>> + - spacemit,k1-apmu-syscon >>>>> + - spacemit,k1-mpmu-syscon >>>>> + - const: syscon >>>>> + - const: simple-mfd >>>>> + >>>>> + reg: >>>>> + maxItems: 1 >>>>> + >>>>> + clock-controller: >>>>> + $ref: /schemas/clock/spacemit,k1-ccu.yaml# >>>>> + type: object >>>> >>>> So now we see the full picture and it leads to questions. >>>> >>>> 1. Why spacemit,k1-apbc-syscon with spacemit,k1-ccu-apmu child is a >>>> correct combination? >>>> >>>> 2. Why having this split in the first place? Please confirm that clock >>>> controller is really, really a separate device and its child in >>>> datasheet. IOW, fake child for your Linux is a no-go. Fake child while >>>> devices are independent is another no-go. >>> >>> These syscons are introduced because the clock controllers share >>> registers with reset controllers. Folding them into the parents results >> >> So a fake split... >> >>> in devicetree nodes act as both reset and clock controllers, like what >> >> Which is correct hardware representation, isn't it? >> >>> has been done for Rockchip SoCs. Such folding isn't practical for the >>> MPMU region either, since watchdog and other misc bits (e.g. PLL lock >>> status) locates in it. > > I have to correct that the watchdog doesn't stay in the MPMU region, I > misremembered it. > >> Hm? Why? You have a device which is reset and clock controller, so why >> one device node is not practical? Other vendors do not have problem with >> this. > > Merging reset and clock controllers together is fine to me. What I want > to mention is that APMU and MPMU, abbreviated from Application/Main Power > Management Unit, contain not only clock/reset-related registers but also > power management ones[1]. Additionally, the PLL lock status bits locate > at MPMU, split from the PLL configuration registers as you've already > seen in the binding of spacemit,k1-ccu-apbs where I refer to it with a > phandle. You need to define what is the device here. Don't create fake nodes just for your drivers. If registers are interleaved and manual says "this is block APMU/MPMU" then you have one device, so one node with 'reg'. If subblocks are re-usable hardware (unlikely) or at least separate/distinguishable, you could have children. If subblocks are re-usable but addresses are interleaved, then children should not have 'reg'. If children do not have any resources as an effect, this is strong indication these are not re-usable, separate subblocks. > > Since reset/clock and power management registers interleave in the MMIO > region, do you think syscons are acceptable in this situation or it > should be handled in another way? The reset and clock controllers could > still be folded together as they share the same registers. The device > tree will look like, > > syscon_mpmu: system-controller@d4050000 { > compatible = "spacemit,mpmu-syscon", "syscon", "simple-mfd"; > reg = <0xd4050000 0x10000>; > > cru_mpmu: clock-controller { > compatible = "spacemit,k1-cru-mpmu"; > #clock-cells = <1>; > #reset-cells = <1>; > }; > > power_mpmu: power-controller { > compatible = "spacemit,k1-powerdomain-mpmu"; > /* ... */ > #power-domain-cells = <0>; > }; Based on above, I do not see any need for children device nodes. It's fake split to match driver design. > }; > > For the other two clock controllers (APBS and APBC), syscons are really > unnecessary and it's simple to fold them. I don't follow. Do we talk about children or syscon compatible? Best regards, Krzysztof
