[PATCH v9 01/22] dt-bindings: ARM: Mediatek: Add new document bindings of imp i2c wrapper controller

[Chun-Jie Chen]

On Fri, 2021-06-18 at 15:50 +0200, Matthias Brugger wrote:
> 
> On 18/06/2021 08:32, Chen-Yu Tsai wrote:
> > On Wed, Jun 16, 2021 at 2:34 AM Chun-Jie Chen
> > <chun-jie.chen at mediatek.com> wrote:
> > > 
> > > On Fri, 2021-06-11 at 11:56 +0200, Matthias Brugger wrote:
> > > > 
> > > > On 10/06/2021 19:41, Stephen Boyd wrote:
> > > > > Quoting Matthias Brugger (2021-06-08 07:45:49)
> > > > > > 
> > > > > > 
> > > > > > On 07/06/2021 07:20, Chun-Jie Chen wrote:
> > > > > > > On Wed, 2021-06-02 at 12:12 -0500, Rob Herring wrote:
> > > > > > > > > +
> > > > > > > > > +description:
> > > > > > > > > +  The Mediatek imp i2c wrapper controller provides
> > > > > > > > > functional
> > > > > > > > > configurations and clocks to the system.
> > > > > > > > > +
> > > > > > > > > +properties:
> > > > > > > > > +  compatible:
> > > > > > > > > +    items:
> > > > > > > > > +      - enum:
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_c
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_e
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_s
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_ws
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_w
> > > > > > > > > +          - mediatek,mt8192-imp_iic_wrap_n
> > > > > > > > 
> > > > > > > > Looks to me like these are all the same h/w, but just
> > > > > > > > have
> > > > > > > > differing
> > > > > > > > sets of clocks. That's not really a reason to have
> > > > > > > > different
> > > > > > > > compatibles.
> > > > > > > > 
> > > > > > > > If you need to know what clocks are present, you can
> > > > > > > > walk the
> > > > > > > > DT for
> > > > > > > > all 'clocks' properties matching this clock controller
> > > > > > > > instance. Or
> > > > > > > > use
> > > > > > > > 'clock-indices' to define which ones are present.
> > > > > 
> > > > > Is the idea to use clock-indices and then list all the clock
> > > > > ids in
> > > > > there and match them up at driver probe time to register the
> > > > > clocks
> > > > > provided by the IO region? Feels like we'll do a lot of
> > > > > parsing at
> > > > > each
> > > > > boot to match up structures and register clks with the clk
> > > > > framework.
> > > > > 
> > > > > If it's like other SoCs then the clk id maps to a hard macro
> > > > > for a
> > > > > type
> > > > > of clk, and those hard macros have been glued together with
> > > > > other
> > > > > clks
> > > > > and then partitioned into different IO regions to make up a
> > > > > clock
> > > > > controller. Or maybe in this case, those clk hard macros have
> > > > > been
> > > > > scattered into each IP block like SPI, i2c, uart, etc. so
> > > > > that the
> > > > > clock
> > > > > controller doesn't really exist and merely the gates and rate
> > > > > control
> > > > > (mux/divider) for the clk that's clocking some particular IP
> > > > > block
> > > > > all
> > > > > live inside the IP wrapper. If it's this case then I hope
> > > > > there are
> > > > > a
> > > > > bunch of PLLs that are fixed rate so that the i2c clk doesn't
> > > > > have
> > > > > to go
> > > > > outside the wrapper to change frequency (of which there
> > > > > should be
> > > > > two
> > > > > "standard" frequencies anyway).
> > > > > 
> > > > > > > > 
> > > > > > > > Rob
> > > > > > > 
> > > > > > > Some module is divided to sub-modules which are designed
> > > > > > > in
> > > > > > > different
> > > > > > > h/w blocks for different usage, and if we want to use the
> > > > > > > same
> > > > > > > compatible to present these h/w blocks, we need to move
> > > > > > > the
> > > > > > > clock data
> > > > > > > provided by these h/w blocks to dts, but we usually use
> > > > > > > different
> > > > > > > compatible to get the h/w blocks data in
> > > > > > > Mediatek's clock driver, so do you suggest to register
> > > > > > > clock
> > > > > > > provided
> > > > > > > by different h/w blocks using same compatible?
> > > > > > > 
> > > > > > 
> > > > > > The mapping of them is as following:
> > > > > > imp_iic_wrap_c:  11007000
> > > > > > imp_iic_wrap_e:  11cb1000
> > > > > > imp_iic_wrap_s:  11d03000
> > > > > > imp_iic_wrap_ws: 11d23000
> > > > > > imp_iic_wrap_w:  11e01000
> > > > > > imp_iic_wrap_n:  11f02000
> > > > > > 
> > > > > 
> > > > > Sure. What is their purpose though? Are they simply a bunch
> > > > > of
> > > > > different
> > > > > i2c clks?
> > > > > 
> > > > 
> > > > That would be need to be answered by MediaTek as I don't have
> > > > access
> > > > to any
> > > > documentation.
> > > > 
> > > > Regards,
> > > > Matthias
> > > 
> > > We describe which clock controllers are exist in dts and
> > > get the clock data provided by clock controller in driver data
> > > by matching device compatible.
> > > 
> > > The clock data contains several clocks which includes the clock
> > > index,
> > > parent clock source and the details of reg control inside the IP
> > > block
> > > of clock controller.
> > > 
> > > In MT8192 platform, some IP block is divide to several sub-blocks 
> > > and
> > > each sub-block provides clock control by itself.
> > 
> > Some more information:
> > 
> > Based on what I read in the datasheets, I'm guessing that MediaTek
> > groups
> > the I2C controllers into several groups and places them in
> > different parts
> > of the die. The suffix of imp_iic_wrap_XXX is likely pointing to
> > the
> > placement of the group. And the imp_iic_wrap_XXX is what the name
> > suggests
> > a wrapper around the group of I2C controllers. The wrapper contains
> > clock
> > and reset controls, as well as other things that I can't make out.
> > 
> 
> Thanks for the clarification. If the wrapper contains more then just
> clocks,
> then probably we will need a solution as done by MMSYS subsystem.
> Would be good
> if you could work with MediaTek to find out what exactly this
> wrappers contain,
> to get a better picture of if we need an additional driver or not.
> 
> Regards,
> Matthias

+ Kewei

Hi Matthias,

After discuss with i2c owenr(Kewei) in mediatek, although the HW block
of imp_iic_wrap_XXX contains more than just clock, but we only use the
clock part in this HW block and just consider that imp_iic_wrap_XXX is
a pure clock provider.

Thanks!
Best Regards,
Chun-Jie