On Thu, Feb 13, 2025 at 07:07:55PM +0100, Krzysztof Kozlowski wrote: > 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. Okay, I'll make APMU/MPMU act as a whole device without split children and drop bindings for the childern (spacemit,k1-ccu-mpmu) in the next revision. Do I get the point? > > }; > > > > 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? APBS region contains only clock (PLL) bits and APBC region contains only reset and clock bits, so I was thinking about dropping the syscon nodes and changing their compatible to spacemit,k1-plls and spacemit,k1-cru-apbc. In summary, my plan is, - For MPMU, APMU and APBC region, keep the binding in soc/spacemit. They'll be reset, clock and power controllers, with compatible "spacemit,k1-syscon-*". - For APBS region, write a new binding clock/spacemit,k1-plls, as it contains only PLL-related bits. It acts as clock controller. - All split children will be eliminated, there'll be only four device nodes, one for each region, matching the datasheet. - Put all clock-related binding definition of SpacemiT K1 in dt-bindings/clock/spacemit,k1-ccu.h Is it fine for you? > > Best regards, > Krzysztof Thanks, Haylen Chu
