Re: [PATCH v7 1/4] dt-bindings: soc: sophgo: Add Sophgo system control module

[Chen Wang]

On 2024/1/9 3:36, Krzysztof Kozlowski wrote:
> On 08/01/2024 08:20, Chen Wang wrote:
> > On 2024/1/8 15:03, Krzysztof Kozlowski wrote:
> > > On 08/01/2024 07:48, Chen Wang wrote:
> > > > From: Chen Wang <unicorn_wang@xxxxxxxxxxx>
> > > >
> > > > Add documentation to describe Sophgo System Controller for SG2042.
> > > >
> > > > Signed-off-by: Chen Wang <unicorn_wang@xxxxxxxxxxx>
> > > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > > > ---
> > > >    .../soc/sophgo/sophgo,sg2042-sysctrl.yaml     | 34 +++++++++++++++++++
> > > >    1 file changed, 34 insertions(+)
> > > >    create mode 100644 Documentation/devicetree/bindings/soc/sophgo/sophgo,sg2042-sysctrl.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/soc/sophgo/sophgo,sg2042-sysctrl.yaml b/Documentation/devicetree/bindings/soc/sophgo/sophgo,sg2042-sysctrl.yaml
> > > > new file mode 100644
> > > > index 000000000000..1ec1eaa55598
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/soc/sophgo/sophgo,sg2042-sysctrl.yaml
> > > > @@ -0,0 +1,34 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/soc/sophgo/sophgo,sg2042-sysctrl.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Sophgo SG2042 SoC system controller
> > > > +
> > > > +maintainers:
> > > > +  - Chen Wang <unicorn_wang@xxxxxxxxxxx>
> > > > +
> > > > +description:
> > > > +  The Sophgo SG2042 SoC system controller provides register information such
> > > > +  as offset, mask and shift that can be used by other modules, such as clocks.
> > > "offset, mask and shift" is not a register information stored in
> > > syscons. Are you really sure, that your system controller hardware
> > > stores offsets of some other registers?
> > >
> > > Show as some example of such offsets, masks and shifts provided by this
> > > hardware.
> > The system control module is defined here:
> > https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/system-control.rst.
> > It contains some registers related to pll and gates.
> I do not see there registers providing shifts and offsets... just values.

Let me first clarify more what the "offset"/"shift"/"mask" I meant,

Use 
https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/system-control.rst#mpll_control-offset-0x0e8 
as example, this register is used to control Main PLL:

- Offset: 0x0E8, to my understand, it is the offest between this 
MPLL_CONTROL register and the start of system-control base

- Shift: the conlumn "LSB", for example, to locate the field 
MPLL_CONTROL.MPLL_FBDIV, we can first use system-control base + offset 
to get the address of MPLL_CONTROL, then use LSB(16) as shift to get the 
start position of this field.

- Mask:  still use MPLL_CONTROL.MPLL_FBDIV as example, use MSB(27) and 
LSB(16), this means the width of this field is 12 and with this we can 
get bit-mask for this field.

For SG2042, IC define clock related registers in two parts, one is in 
https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/clock.rst, 
and another in 
https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/system-control.rst. 
I define the system control node in DTS and just treat it as a block of 
registers array and after regmap I can get some registers address such 
as MPLL_CONTROL to access it from my driver code.

> > Some other clocks registars are defined in
> > https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/clock.rst.
> >
> > memory-map is defined in
> > https://github.com/sophgo/sophgo-doc/blob/main/SG2042/TRM/source/mmap.rst
>
> Please fix the wording because it does not make sense. System controller
> does not provide register information. Your datasheet provides register
> information.

Sorry, I don't understand why you say "System controller does not 
provide register information."? As I explained above, I did see the 
information about these clock-related registers from the system control 
module, such as the offset/shift/mask I mentioned above. That's why I 
wrote "that can be used by other modules, such as clocks".  How should I 
express, please enlighten me.

Thanks,

Chen

> Best regards,
> Krzysztof