RE: [PATCH v2 1/2] dt-bindings: firmware: arm,scmi: Add properties for i.MX95 Pinctrl OEM extensions

[Peng Fan <peng.fan@xxxxxxx>]

> Subject: RE: [PATCH v2 1/2] dt-bindings: firmware: arm,scmi: Add properties
> for i.MX95 Pinctrl OEM extensions
> 
> Hi Rob, Sudeep, Cristian, Linus

Is it ok to use fsl,pins for i.MX95 SCMI pins, just like previous i.MX processors?
In this way, I need write a new driver, could not reuse pinctrl-scmi.c for i.MX95.
+        properties:
+          fsl,pins:
+            description:
+              each entry consists of 6 integers and represents the mux and config
+              setting for one pin. The first 5 integers <mux_reg conf_reg input_reg
+              mux_val input_val> are specified using a PIN_FUNC_ID macro, which can
+              be found in <arch/arm64/boot/dts/freescale/imx95-pinfunc.h>. The last
+              integer CONFIG is the pad setting value like pull-up on this pin. Please
+              refer to i.MX95 Plus Reference Manual for detailed CONFIG settings.
+            $ref: /schemas/types.yaml#/definitions/uint32-matrix
+            items:
+              items:
+                - description: |
+                    "mux_reg" indicates the offset of mux register.
+                - description: |
+                    "conf_reg" indicates the offset of pad configuration register.
+                - description: |
+                    "input_reg" indicates the offset of select input register.
+                - description: |
+                    "mux_val" indicates the mux value to be applied.
+                - description: |
+                    "input_val" indicates the select input value to be applied.
+                - description: |
+                    "pad_setting" indicates the pad configuration value to be applied.


Thanks,
Peng.
> 
> Although this is dt-binding stuff, I hope you could also help suggest how to
> support NXP SCMI OEM extensions. There is less chance NXP will change
> SCMI firmware to make linux happy using generic conf stuff, because the
> SCMI firmware will also need to work for FreeRTOS/GHS/QNX and etc.
> 
> > Subject: Re: [PATCH v2 1/2] dt-bindings: firmware: arm,scmi: Add
> > properties for i.MX95 Pinctrl OEM extensions
> >
> > On Thu, Apr 25, 2024 at 09:06:00AM +0000, Peng Fan wrote:
> > > Hi Rob,
> > >
> > > > Subject: Re: [PATCH v2 1/2] dt-bindings: firmware: arm,scmi: Add
> > > > properties for i.MX95 Pinctrl OEM extensions
> > > >
> > > > On Thu, Apr 18, 2024 at 10:53:17AM +0800, Peng Fan (OSS) wrote:
> > > > > From: Peng Fan <peng.fan@xxxxxxx>
> > > > >
> > > > > i.MX95 Pinctrl is managed by SCMI firmware using OEM extensions.
> > > > > This patch is to add i.MX95 Pinctrl OEM extensions properties.
> > > > >
> > > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > > > > ---
> > > > >  .../devicetree/bindings/firmware/arm,scmi.yaml     |  9 ++-
> > > > >  .../bindings/firmware/nxp,imx95-scmi-pinctrl.yaml  | 66
> > > > > ++++++++++++++++++++++
> > > > >  2 files changed, 72 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> > > > > b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> > >
> > > ....
> > >
> > > > > +
> > > > > +title: i.MX System Control and Management Interface (SCMI)
> > > > > +Pinctrl Protocol
> > > > > +
> > > > > +maintainers:
> > > > > +  - Peng Fan <peng.fan@xxxxxxx>
> > > > > +
> > > > > +patternProperties:
> > > > > +  '[a-f0-9]+$':
> > > > > +    type: object
> > > > > +    unevaluatedProperties: false
> > > > > +
> > > > > +    properties:
> > > > > +      pins:
> > > > > +        $ref: /schemas/types.yaml#/definitions/string
> > > > > +        description: name of the pin
> > > > > +        items:
> > > > > +          enum: [ daptdi, daptmsswdio, daptclkswclk, daptdotraceswo,
> > > > > +                  gpioio00, gpioio01, gpioio02, gpioio03,
> > > > > + gpioio04,
> > > >
> > > > ioio?
> > >
> > > Yes. The name is exported from SCMI firmware.
> > >
> > > >
> > > > > +                  gpioio05, gpioio06, gpioio07, gpioio08, gpioio09,
> > > > > +                  gpioio10, gpioio11, gpioio12, gpioio13, gpioio14,
> > > > > +                  gpioio15, gpioio16, gpioio17, gpioio18, gpioio19,
> > > > > +                  gpioio20, gpioio21, gpioio22, gpioio23, gpioio24,
> > > > > +                  gpioio25, gpioio26, gpioio27, gpioio28, gpioio29,
> > > > > +                  gpioio30, gpioio31, gpioio32, gpioio33, gpioio34,
> > > > > +                  gpioio35, gpioio36, gpioio37, ccmclko1, ccmclko2,
> > > > > +                  ccmclko3, ccmclko4, enet1mdc, enet1mdio, enet1td3,
> > > > > +                  enet1td2, enet1td1, enet1td0, enet1txctl, enet1txc,
> > > > > +                  enet1rxctl, enet1rxc, enet1rd0, enet1rd1, enet1rd2,
> > > > > +                  enet1rd3, enet2mdc, enet2mdio, enet2td3, enet2td2,
> > > > > +                  enet2td1, enet2td0, enet2txctl, enet2txc, enet2rxctl,
> > > > > +                  enet2rxc, enet2rd0, enet2rd1, enet2rd2, enet2rd3,
> > > > > +                  sd1clk, sd1cmd, sd1data0, sd1data1, sd1data2, sd1data3,
> > > > > +                  sd1data4, sd1data5, sd1data6, sd1data7, sd1strobe,
> > > > > +                  sd2vselect, sd3clk, sd3cmd, sd3data0, sd3data1,
> > > > > +                  sd3data2, sd3data3, xspi1data0, xspi1data1, xspi1data2,
> > > > > +                  xspi1data3, xspi1data4, xspi1data5, xspi1data6,
> > > > > +                  xspi1data7, xspi1dqs, xspi1sclk, xspi1ss0b, xspi1ss1b,
> > > > > +                  sd2cdb, sd2clk, sd2cmd, sd2data0, sd2data1, sd2data2,
> > > > > +                  sd2data3, sd2resetb, i2c1scl, i2c1sda, i2c2scl, i2c2sda,
> > > > > +                  uart1rxd, uart1txd, uart2rxd, uart2txd, pdmclk,
> > > > > +                  pdmbitstream0, pdmbitstream1, sai1txfs, sai1txc,
> > > > > +                  sai1txd0, sai1rxd0, wdogany, fccuerr0 ]
> > > > > +
> > > > > +      nxp,func-id:
> > > > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +        description: Indicates the PAD connections which
> > > > > + function module
> > > >
> > > > The description makes no sense...
> > >
> > > I will use below description in v3:
> > > For each pin, there are up to 8 muxing options (called ALT modes).
> > > For
> > example:
> > > Select 1 of 5 iomux modes to be used for pad: DAP_TCLK_SWCLK.
> > > 000b - Select mux mode: ALT0 mux port: JTAG_MUX_TCK of instance:
> > > jtag_mux 010b - Select mux mode: ALT2 mux port: CAN4_RX of instance:
> > > imx95_wakeupmix_top 100b - Select mux mode: ALT4 mux port:
> > > FLEXIO1_FLEXIO30 of instance: imx95_wakeupmix_top 101b - Select mux
> > > mode: ALT5 mux port: GPIO3_IO30 of instance: imx95_wakeupmix_top
> > 110b
> > > - Select mux mode: ALT6 mux port: LPUART5_CTS_B of instance:
> > imx95_wakeupmix_top The nxp,func-id property is selecting one ALT mode.
> >
> > Looks like constraints on the values. Please add schema for them. I
> > don't think you need to list an example.
> 
> Will add maxItems: 8, minItems: 1
> >
> > Perhaps you should be using 'pinmux' property. That is the standard
> > way to specify a numeric mux mode.
> 
> Ok let me try.
> 
> >
> >
> > > >
> > > > > +
> > > > > +      nxp,pin-conf:
> > > > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +        description: The PAD configuration
> > > >
> > > > PAD stands for? Or is it pin configuration as the property name says?
> > >
> > > It is pin configuration which includes pull up/down, drive strength and etc.
> > >
> > > >
> > > > This is just a raw register values?
> > >
> > > Yes.
> > >
> > > Why can't standard pinctrl properties be
> > > > used here. What's the point of using SCMI pinctrl if you are just
> > > > shuttling register values to SCMI?
> > >
> > > Standard pinctrl properties will need more memory in our SCMI
> > > firmware design. We have limited on-chip memory for SCMI firmware
> usage.
> >
> > Then maybe you shouldn't be using SCMI and just write a pinctrl driver.
> 
> I think I have to. pinctrl-scmi-imx.c was not preferred by ARM SCMI
> maintainer.
> 
> If Linus, Cristian, Sudeep are ok, I could add back pinctrl-scmi-imx.c for some
> OEM mapping/unmapping stuff.
> 
> > Or, Linux has to parse the DT anyways, so use standard properties and
> > transform them into your register values and send that to SCMI.
> 
> Cristian, Sudeep, Linus,
> 
> Is this ok for you? Before sending to SCMI, linux driver transform the bits into
> register value, and send to SCMI firmware.
> 
> >
> > > > > +
> > > > > +      nxp,daisy-id:
> > > > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +        description: The select input register ID
> > > > > +
> > > > > +      nxp,daisy-conf:
> > > > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +        description: The select input register value
> > > >
> > > > I remember some daisy chaining stuff in iomuxc, but otherwise
> > > >
> > > > What's the relationship between these 2 properties? Is it valid if
> > > > only
> > > > 1 is present? I doubt it.
> > >
> > > The scmi firmware will convert the daisy-id into register address,
> > > and write the daisy-conf value into the register.
> > >
> > >  Looks like an address and value pair. Either the
> > > > schema needs to define allowed combinations
> > >
> > > The firmware will check whether id and conf is valid, is there a
> > > need to
> > define
> > > allowed combinations? There will be lots of check to define allowed
> > > combinations.
> >
> > The firmware can't check that the DT contains nxp,daisy-id but not
> > nxp,daisy-conf or vice-versa. Of course the kernel could check that,
> > but validating the DT is not the kernel's job.
> >
> >
> > >  or design the properties in a
> > > > way you don't have too. IOW, make a single property that's a tuple
> > > > of
> > register
> > > > ID and value.
> > >
> > > Define tuple will make the property not able to use linux generic
> > > pinconf driver. The current parse_dt_cfg for custom_dt_params only
> > > support a single u32 value and not easy to support tuple.
> >
> > Sounds like a Linux problem. We're talking about bindings. Fix Linux
> > if it doesn't meet your needs.
> >
> >
> > How many bits of id and conf do you need? This too could just be part
> > of 'pinmux' property. It's value is entirely h/w specific and up to you.
> > You just need to fit it into 32-bits (though we could perhaps enlarge
> > it).
> 
> For conf, 4 bits is find. For id, 12 bits is fine I think.
> 
> Using pinmux property with some vendor handing code. Not sure ARM SCMI
> maintainer is happy or not.
> 
> Thanks,
> Peng.
> 
> >
> > Rob