[PATCH v1 1/2] Documentation: dt: reset: add mediatek,syscon-reset binding

[Conor Dooley]

On Wed, Jul 01, 2026 at 06:35:20AM +0000, Peter Wang (王信友) wrote:
> On Fri, 2026-06-26 at 10:33 +0200, Philipp Zabel wrote
> > 
> > Where is the binding doc for mediatek,mt8183-ufs0cfg_ao? Is this
> > simple-mfd just to load the reset driver?
> > 
> 
> Hi Philipp,
> 
> Thanks for the review, and sorry for the late reply.
> Yes, "mediatek,mt8183-ufs0cfg_ao" should be removed.
> I will remove it in the next version.
> 
> > > +        reg = <0x16840000 0x1000>;
> > > +        #address-cells = <1>;
> > > +        #size-cells = <1>;
> > > +
> > > +        ufs0cfgao_rst: reset-controller {
> > > +            compatible = "mediatek,syscon-reset";
> > 
> > It looks to me like this is just two registers inside ufs0cfg_ao, not
> > a
> > separate device. Why don't you just add #reset-cells to the parent
> > node?
> > 
> > > +            #reset-cells = <1>;
> > > +            mediatek,reset-bits =
> > > +                <0x48  3  0x4c  3  100>,
> > > +                <0x148 0  0x14c 0  100>,
> > > +                <0x148 1  0x14c 1  100>,
> > > +                <0x148 2  0x14c 2  0>;
> > > +        };
> > 
> > Why is this in DT? This should be a table in the reset driver.
> > 
> > regards
> > Philipp
> 
> Regarding the child node and reset-bits in DT,
> We chose the child node approach with 'mediatek,reset-bits' defined 
> in DT to keep the reset line descriptions self-contained and reusable 
> across different SoC variants. MediaTek has many SoCs (mt8183, mt6985, 
> mt6989, ...) where the same UFS subsystem may have different register 
> offsets for reset lines. By describing them in DT, we can support new 
> SoC variants by updating the DT alone, without requiring a new driver 
> patch for every new SoC.

From what I recall, mediatek ufs is a mess with lots of vendor kernel
type things slipping into mainline without proper review on the DT
front.
Because of that, I at least am going to require that everything is done
completely (and perhaps excessively) by the book here, including
introducing complete bindings for syscon regions rather than partial
bits for components like this one.

> This approach is also consistent with the existing 'ti,syscon-reset' 
> binding, which uses a similar per-entry table property 'ti,reset-bits' 
> to describe reset lines within a syscon block.

This was done about 10 years ago, I would not consider it a guide for
what's acceptable today.

Thanks,
Conor.
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