Re: [PATCH v8 1/3] dt-bindings: mmc: mtk-sd: extend interrupts and pinctrls properties

[Axe Yang <axe.yang@mediatek.com>]

Hi Rob,

Sorry, my last mail may mislead your understanding. Let me explain more
about this.

On Tue, 2022-03-22 at 11:42 -0500, Rob Herring wrote:
> On Tue, Mar 22, 2022 at 05:33:55PM +0800, Axe Yang wrote:
> > Hello AngeloGioacchino,
> > 
> > On Tue, 2022-03-22 at 09:42 +0100, AngeloGioacchino Del Regno
> > wrote:
> > > Il 22/03/22 02:35, Axe Yang ha scritto:
> > > > On Mon, 2022-03-21 at 18:29 -0500, Rob Herring wrote:
> > > > > On Mon, Mar 21, 2022 at 07:51:32PM +0800, Axe Yang wrote:
> > > > > > Extend interrupts and pinctrls for SDIO wakeup interrupt
> > > > > > feature.
> > > > > > This feature allow SDIO devices alarm asynchronous
> > > > > > interrupt to
> > > > > > host
> > > > > > even when host stop providing clock to SDIO card. An extra
> > > > > > wakeup
> > > > > > interrupt and pinctrl states for SDIO DAT1 pin state
> > > > > > switching
> > > > > > are
> > > > > > required in this scenario.
> > > > > > 
> > > > > > Signed-off-by: Axe Yang <axe.yang@mediatek.com>
> > > > > > ---
> > > > > >   .../devicetree/bindings/mmc/mtk-sd.yaml       | 23
> > > > > > ++++++++++++++++++-
> > > > > >   1 file changed, 22 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/Documentation/devicetree/bindings/mmc/mtk-
> > > > > > sd.yaml
> > > > > > b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > > > > index 297ada03e3de..f57774535a1d 100644
> > > > > > --- a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > > > > +++ b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > > > > @@ -69,12 +69,23 @@ properties:
> > > > > >         - const: ahb_cg
> > > > > >   
> > > > > >     interrupts:
> > > > > > -    maxItems: 1
> > > > > > +    description:
> > > > > > +      Should at least contain MSDC GIC interrupt. To
> > > > > > support
> > > > > > SDIO
> > > > > > in-band wakeup, an extended
> > > > > > +      interrupt is required and be configured as wakeup
> > > > > > source
> > > > > > irq.
> > > > > > +    minItems: 1
> > > > > > +    maxItems: 2
> > > > > >   
> > > > > >     pinctrl-names:
> > > > > > +    description:
> > > > > > +      Should at least contain default and state_uhs. To
> > > > > > support
> > > > > > SDIO in-band wakeup, dat1 pin
> > > > > > +      will be switched between GPIO mode and SDIO DAT1
> > > > > > mode,
> > > > > > state_eint and state_dat1 are
> > > > > > +      mandatory in this scenarios.
> > > > > > +    minItems: 2
> > > > > >       items:
> > > > > >         - const: default
> > > > > >         - const: state_uhs
> > > > > > +      - const: state_eint
> > > > > > +      - const: state_dat1
> > > > > >   
> > > > > >     pinctrl-0:
> > > > > >       description:
> > > > > > @@ -86,6 +97,16 @@ properties:
> > > > > >         should contain uhs mode pin ctrl.
> > > > > >       maxItems: 1
> > > > > >   
> > > > > > +  pinctrl-2:
> > > > > > +    description:
> > > > > > +      should switch dat1 pin to GPIO mode.
> > > > > > +    maxItems: 1
> > > > > > +
> > > > > > +  pinctrl-3:
> > > > > > +    description:
> > > > > > +      should switch SDIO dat1 pin from GPIO mode back to
> > > > > > SDIO
> > > > > > mode.
> > > > > 
> > > > > How is this different than pinctrl-0?
> > > > 
> > > > pinctrl-0 contains default settings for all IO
> > > > pins(CLK/CMD/DAT).
> > > > pinctrl-1 contains settings for all IO pins(CLK/CMD/DAT) in UHS
> > > > mode.
> > > > pinctrl-3 is lightweight pinctrl-1, only keep SDIO DAT1 pin
> > > > function
> > > > switch part.
> > > > 
> > > 
> > > Is there any particular reason why we cannot simply select
> > > pinctrl-1
> > > again
> > > instead of pinctrl-3, apart from the virtually not existent
> > > overhead
> > > of one more mmio write?
> > 
> > No, there is no particular reason. 
> > I just want to do the pin function switch quick and clean. 
> > 
> > The intention of pinctrl-1 is to set the most initial state of IO
> > pins
> > in UHS mode. If I don't need to adjust IO settings any longer, it
> > is
> > okay to select pinctrl-1 state instead of pinctrl-3. 
> > But think about this scenarios: after initial SDIO IO pins to UHS
> > mode,
> > I want to adjust some IO related properties, such as driving
> > strength.
> > And I want to keep these settings because with new driving
> > strength,
> > the signal is better. I'd rather to choose pinctrl-3 but not
> > pinctrl-1, 
> > because I do not want the change be restored after next runtime
> > resume.
> 
> The pinctrl-X properties set modes, they aren't supposed to be a
> state 
> machine

I do use the pinctl-x properties to set modes, but not judge state from
pin state.

I need to time-multiplex SDIO DAT1 pin, shift it between GPIO mode and
SDIO IO mode, for example:

mmc2_pins_default {
	...
};

mmc2_pins_uhs {
        pins_clk {
                pinmux = <PINMUX_GPIO170__FUNC_B1_MSDC2_CLK>;
                drive-strength = <MTK_DRIVE_4mA>;
                bias-pull-down = <MTK_PUPD_SET_R1R0_10>;
        };

        pins_cmd_dat {
                pinmux = <PINMUX_GPIO169__FUNC_B1_MSDC2_CMD>,
                         <PINMUX_GPIO171__FUNC_B1_MSDC2_DAT0>,
                         <PINMUX_GPIO172__FUNC_B1_MSDC2_DAT1>,
                         <PINMUX_GPIO173__FUNC_B1_MSDC2_DAT2>,
                         <PINMUX_GPIO174__FUNC_B1_MSDC2_DAT3>;
                input-enable;
                drive-strength = <MTK_DRIVE_6mA>;
                bias-pull-up = <MTK_PUPD_SET_R1R0_01>;
        };
};

mmc2_pins_eint {
        pins_dat1 {
                pinmux = <PINMUX_GPIO172__FUNC_B_GPIO172>;
                input-enable;
                bias-pull-up = <MTK_PUPD_SET_R1R0_01>;
        };
};

mmc2_pins_dat1 {
        pins_dat1 {
                pinmux = <PINMUX_GPIO172__FUNC_B1_MSDC2_DAT1>;
                input-enable;
                bias-pull-up = <MTK_PUPD_SET_R1R0_01>;
        };
};

The pinctrl-1(mmc2_pin_uhs) here contain all SDIO IO pins, for the most
early initialize. I SELECT pinctrl-1 when I change SDIO to SDR104 mode,
before calibration.
And when SDIO bus is idle, I SELECT pinctrl-2(mmc2_pins_eint), use DAT1
as a interrupt line when steping into runtime suspend.
After resume, I SELECT pinctrl-3(mmc2_pins_dat1) to set DAT1 pin back
to SDIO IO mode.

I need all the pinctrl-x properties, and take the initiative to set pin
mode according to needs.


Best Regard,
Axe