[2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
diff mbox

Message ID 1494830906-6442-3-git-send-email-aisheng.dong@nxp.com
State New
Headers show

Commit Message

Aisheng Dong May 15, 2017, 6:48 a.m. UTC
Do not assume MUX 0 is GPIO function in core driver as a different
SoC may have different value. e.g. MX7ULP Mux 1 is GPIO.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Fugang Duan <fugang.duan@nxp.com>
Cc: Bai Ping <ping.bai@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Stefan Agner May 15, 2017, 5:27 p.m. UTC | #1
On 2017-05-14 23:48, Dong Aisheng wrote:
> Do not assume MUX 0 is GPIO function in core driver as a different
> SoC may have different value. e.g. MX7ULP Mux 1 is GPIO.
> 
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Alexandre Courbot <gnurou@gmail.com>
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Stefan Agner <stefan@agner.ch>
> Cc: Fugang Duan <fugang.duan@nxp.com>
> Cc: Bai Ping <ping.bai@nxp.com>
> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> ---
>  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> b/drivers/pinctrl/freescale/pinctrl-imx.c
> index 0d6aaca..ed8ea32 100644
> --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
> pinctrl_dev *pctldev,
>  			continue;
>  		for (pin = 0; pin < grp->num_pins; pin++) {
>  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
> -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
> +			if (imx_pin->pin == offset)
>  				goto mux_pin;

The reason I added that check was to make sure we pick a mux option
which is GPIO... With this change, any pinmux might be picked...

>  		}
>  	}
> @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
> pinctrl_dev *pctldev,
>  	reg = readl(ipctl->base + pin_reg->mux_reg);
>  	reg &= ~info->mux_mask;
>  	reg |= imx_pin->config;
> +	reg |= imx_pin->mux_mode << info->mux_shift;

... and muxed...

Not sure if we want that.

I had to control GPIO output/input through pinctrl since Vybrid does not
allow to control that from the GPIO block.

However, according to your GPIO patchset, the i.MX 7ULP has a new
register GPIO_PDDR to control output from the GPIO block. Is controlling
the output driver from IOMUXC still required? If not, I really would
just not use all that "find pinctrl config" hackery... e.g. add a new
flag, USE_IOMUXC_FOR_GPIO_OUTPUT, and set that only for Vybrid.

This would also align much better with the other i.MX devices, where
pinmuxing and GPIO is completely orthogonal.

--
Stefan

>  	writel(reg, ipctl->base + pin_reg->mux_reg);
>  
>  	return 0;
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Aisheng Dong May 17, 2017, 7:18 a.m. UTC | #2
> -----Original Message-----
> From: Stefan Agner [mailto:stefan@agner.ch]
> Sent: Tuesday, May 16, 2017 1:27 AM
> To: A.S. Dong
> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> kernel@pengutronix.de; Alexandre Courbot
> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
> 
> On 2017-05-14 23:48, Dong Aisheng wrote:
> > Do not assume MUX 0 is GPIO function in core driver as a different SoC
> > may have different value. e.g. MX7ULP Mux 1 is GPIO.
> >
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Alexandre Courbot <gnurou@gmail.com>
> > Cc: Shawn Guo <shawnguo@kernel.org>
> > Cc: Stefan Agner <stefan@agner.ch>
> > Cc: Fugang Duan <fugang.duan@nxp.com>
> > Cc: Bai Ping <ping.bai@nxp.com>
> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> > ---
> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> > b/drivers/pinctrl/freescale/pinctrl-imx.c
> > index 0d6aaca..ed8ea32 100644
> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> > @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
> > pinctrl_dev *pctldev,
> >  			continue;
> >  		for (pin = 0; pin < grp->num_pins; pin++) {
> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
> > +			if (imx_pin->pin == offset)
> >  				goto mux_pin;
> 
> The reason I added that check was to make sure we pick a mux option which
> is GPIO... With this change, any pinmux might be picked...
> 

First of all, this seems to be wrong to me that GPIO mux mode is SoC
Dependant and should not be put in pinctrl-imx core driver.

Secondly, I think we may be over worried and it's not quite necessary
As we did not do the sanity check for both raw config and mux data read
From Device tree, why only do it for GPIO?

We may trust the data in device tree.

> >  		}
> >  	}
> > @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
> > pinctrl_dev *pctldev,
> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
> >  	reg &= ~info->mux_mask;
> >  	reg |= imx_pin->config;
> > +	reg |= imx_pin->mux_mode << info->mux_shift;
> 
> ... and muxed...
> 
> Not sure if we want that.
> 
> I had to control GPIO output/input through pinctrl since Vybrid does not
> allow to control that from the GPIO block.
> 
> However, according to your GPIO patchset, the i.MX 7ULP has a new register
> GPIO_PDDR to control output from the GPIO block. Is controlling the output
> driver from IOMUXC still required? 

Yes, it's still required.

> If not, I really would just not use all
> that "find pinctrl config" hackery... e.g. add a new flag,
> USE_IOMUXC_FOR_GPIO_OUTPUT, and set that only for Vybrid.
> 
> This would also align much better with the other i.MX devices, where
> pinmuxing and GPIO is completely orthogonal.
> 

Actually this patch came only because to make the exist code
not break MX7ULP.

Actually I'm wondering why we need implement 
imx_pmx_gpio_request_enable function?

Per my understanding, IMX binding already set GPIO mux by
Parsing MUX mode from device tree, so why need gpio_request_enable
which looks like is duplicated.

Can you help explain it?

Regards
Dong Aisheng

> --
> Stefan
> 
> >  	writel(reg, ipctl->base + pin_reg->mux_reg);
> >
> >  	return 0;
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Stefan Agner May 17, 2017, 6:16 p.m. UTC | #3
On 2017-05-17 00:18, A.S. Dong wrote:
>> -----Original Message-----
>> From: Stefan Agner [mailto:stefan@agner.ch]
>> Sent: Tuesday, May 16, 2017 1:27 AM
>> To: A.S. Dong
>> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
>> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
>> kernel@pengutronix.de; Alexandre Courbot
>> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
>>
>> On 2017-05-14 23:48, Dong Aisheng wrote:
>> > Do not assume MUX 0 is GPIO function in core driver as a different SoC
>> > may have different value. e.g. MX7ULP Mux 1 is GPIO.
>> >
>> > Cc: Linus Walleij <linus.walleij@linaro.org>
>> > Cc: Alexandre Courbot <gnurou@gmail.com>
>> > Cc: Shawn Guo <shawnguo@kernel.org>
>> > Cc: Stefan Agner <stefan@agner.ch>
>> > Cc: Fugang Duan <fugang.duan@nxp.com>
>> > Cc: Bai Ping <ping.bai@nxp.com>
>> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
>> > ---
>> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
>> >  1 file changed, 2 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
>> > b/drivers/pinctrl/freescale/pinctrl-imx.c
>> > index 0d6aaca..ed8ea32 100644
>> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
>> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
>> > @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
>> > pinctrl_dev *pctldev,
>> >  			continue;
>> >  		for (pin = 0; pin < grp->num_pins; pin++) {
>> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
>> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
>> > +			if (imx_pin->pin == offset)
>> >  				goto mux_pin;
>>
>> The reason I added that check was to make sure we pick a mux option which
>> is GPIO... With this change, any pinmux might be picked...
>>
> 
> First of all, this seems to be wrong to me that GPIO mux mode is SoC
> Dependant and should not be put in pinctrl-imx core driver.

Hm, agree, we should consider to move
imx_pmx_gpio_request_enable/disable_free and imx_pmx_gpio_set_direction
into pinctrl-vf610.c

> 
> Secondly, I think we may be over worried and it's not quite necessary
> As we did not do the sanity check for both raw config and mux data read
> From Device tree, why only do it for GPIO?
> 
> We may trust the data in device tree.

In Vybrid, there is no need to explicitly assign a pinmux to use a pin
as GPIO. So the pinmux could be anything... The implemented semantics
for Vyrbid is really different than i.MX, see below.

> 
>> >  		}
>> >  	}
>> > @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
>> > pinctrl_dev *pctldev,
>> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
>> >  	reg &= ~info->mux_mask;
>> >  	reg |= imx_pin->config;
>> > +	reg |= imx_pin->mux_mode << info->mux_shift;
>>
>> ... and muxed...
>>
>> Not sure if we want that.
>>
>> I had to control GPIO output/input through pinctrl since Vybrid does not
>> allow to control that from the GPIO block.
>>
>> However, according to your GPIO patchset, the i.MX 7ULP has a new register
>> GPIO_PDDR to control output from the GPIO block. Is controlling the output
>> driver from IOMUXC still required?
> 
> Yes, it's still required.
> 

That sounds weird, what is the GPIO_PDDR for then? Sure I  need to
enable the output driver to drive the pin, but can I disable output just
using GPIO_PDDR?

Maybe we have a miss understanding here:

Lets assume we want to switch a GPIO between output and input:

echo "output" > /sys/class/gpio/gpioN/direction
..
echo "input" > /sys/class/gpio/gpioN/direction

Do I need to disable the output driver in the IOMUXC or can we just
disable GPIO_PDDR and use the pin as input?

If we can disable the output driver just using GPIO_PDDR, we can avoid
the gpio_set_direction cross call.


>> If not, I really would just not use all
>> that "find pinctrl config" hackery... e.g. add a new flag,
>> USE_IOMUXC_FOR_GPIO_OUTPUT, and set that only for Vybrid.
>>
>> This would also align much better with the other i.MX devices, where
>> pinmuxing and GPIO is completely orthogonal.
>>
> 
> Actually this patch came only because to make the exist code
> not break MX7ULP.
> 
> Actually I'm wondering why we need implement 
> imx_pmx_gpio_request_enable function?
> 
> Per my understanding, IMX binding already set GPIO mux by
> Parsing MUX mode from device tree, so why need gpio_request_enable
> which looks like is duplicated.
> 
> Can you help explain it?

I suggest to read this clarification email wrt to pinctrl/gpio from
Linus Walleij:
https://lkml.org/lkml/2016/10/10/87

To summarize: We have different semantics in Vybrid: The GPIO subsystem
automatically mux the GPIO for you. So in Vybrid, you do not have to mux
a GPIO (but a valid entry in your device tree is needed, but does not
assigned to any node).

Is what the driver is doing for Vybrid wrong? It is different from i.MX,
but afaik, it is not really wrong... Its a valid implementation
according to the currently defined semantics...  Due to the *need* to
touch pinctrl for direction, I had to implement cross calls anyway, so I
thought I might as well go full mile and also mux the GPIO on request...

So the question is, what semantic do we want for i.MX 7ULP? Since it is
a i.MX device, we probably want the same semantics as i.MX 6/7 is
already using for the sake of consistency. So in this case the
gpio_request_enable/disable callbacks are not needed...

This is how I hope we can do the implementation for i.MX 7ULP:
- Do not use gpio_request_enable/disable
- Do not use gpio_set_direction either
- Users using a GPIO should enable output driver in IOMUXC (just use a
pin configuration where output driver is enabled)
- The GPIO driver only enables/disables the output driver using its
GPIO_PDDR register depending on GPIO direction

--
Stefan
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Aisheng Dong May 18, 2017, 7 a.m. UTC | #4
> -----Original Message-----
> From: Stefan Agner [mailto:stefan@agner.ch]
> Sent: Thursday, May 18, 2017 2:16 AM
> To: A.S. Dong
> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> kernel@pengutronix.de; Alexandre Courbot
> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
> 
> On 2017-05-17 00:18, A.S. Dong wrote:
> >> -----Original Message-----
> >> From: Stefan Agner [mailto:stefan@agner.ch]
> >> Sent: Tuesday, May 16, 2017 1:27 AM
> >> To: A.S. Dong
> >> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> >> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> >> kernel@pengutronix.de; Alexandre Courbot
> >> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is
> >> gpio
> >>
> >> On 2017-05-14 23:48, Dong Aisheng wrote:
> >> > Do not assume MUX 0 is GPIO function in core driver as a different
> >> > SoC may have different value. e.g. MX7ULP Mux 1 is GPIO.
> >> >
> >> > Cc: Linus Walleij <linus.walleij@linaro.org>
> >> > Cc: Alexandre Courbot <gnurou@gmail.com>
> >> > Cc: Shawn Guo <shawnguo@kernel.org>
> >> > Cc: Stefan Agner <stefan@agner.ch>
> >> > Cc: Fugang Duan <fugang.duan@nxp.com>
> >> > Cc: Bai Ping <ping.bai@nxp.com>
> >> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> >> > ---
> >> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
> >> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > index 0d6aaca..ed8ea32 100644
> >> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
> >> > pinctrl_dev *pctldev,
> >> >  			continue;
> >> >  		for (pin = 0; pin < grp->num_pins; pin++) {
> >> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
> >> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
> >> > +			if (imx_pin->pin == offset)
> >> >  				goto mux_pin;
> >>
> >> The reason I added that check was to make sure we pick a mux option
> >> which is GPIO... With this change, any pinmux might be picked...
> >>
> >
> > First of all, this seems to be wrong to me that GPIO mux mode is SoC
> > Dependant and should not be put in pinctrl-imx core driver.
> 
> Hm, agree, we should consider to move
> imx_pmx_gpio_request_enable/disable_free and imx_pmx_gpio_set_direction
> into pinctrl-vf610.c
> 

IMX7ULP may want to use imx_pmx_gpio_set_direction as well to support
dynamically change GPIO from output to input.

> >
> > Secondly, I think we may be over worried and it's not quite necessary
> > As we did not do the sanity check for both raw config and mux data
> > read From Device tree, why only do it for GPIO?
> >
> > We may trust the data in device tree.
> 
> In Vybrid, there is no need to explicitly assign a pinmux to use a pin as
> GPIO. So the pinmux could be anything... The implemented semantics for
> Vyrbid is really different than i.MX, see below.
> 

Strange, I do see Vybrid assigning pinmux to GPIO in device tree.
e.g.
arch/arm/boot/dts/vf-colibri.dtsi
pinctrl_esdhc1: esdhc1grp {
        fsl,pins = <
                VF610_PAD_PTA24__ESDHC1_CLK     0x31ef
                VF610_PAD_PTA25__ESDHC1_CMD     0x31ef
                VF610_PAD_PTA26__ESDHC1_DAT0    0x31ef
                VF610_PAD_PTA27__ESDHC1_DAT1    0x31ef
                VF610_PAD_PTA28__ESDHC1_DATA2   0x31ef
                VF610_PAD_PTA29__ESDHC1_DAT3    0x31ef
                VF610_PAD_PTB20__GPIO_42        0x219d
        >;
};  

> >
> >> >  		}
> >> >  	}
> >> > @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
> >> > pinctrl_dev *pctldev,
> >> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
> >> >  	reg &= ~info->mux_mask;
> >> >  	reg |= imx_pin->config;
> >> > +	reg |= imx_pin->mux_mode << info->mux_shift;
> >>
> >> ... and muxed...
> >>
> >> Not sure if we want that.
> >>
> >> I had to control GPIO output/input through pinctrl since Vybrid does
> >> not allow to control that from the GPIO block.
> >>
> >> However, according to your GPIO patchset, the i.MX 7ULP has a new
> >> register GPIO_PDDR to control output from the GPIO block. Is
> >> controlling the output driver from IOMUXC still required?
> >
> > Yes, it's still required.
> >
> 
> That sounds weird, what is the GPIO_PDDR for then? Sure I  need to enable
> the output driver to drive the pin, but can I disable output just using
> GPIO_PDDR?

No, to fully disable a output, you must disable OBE as well.

> 
> Maybe we have a miss understanding here:
> 
> Lets assume we want to switch a GPIO between output and input:
> 
> echo "output" > /sys/class/gpio/gpioN/direction ..
> echo "input" > /sys/class/gpio/gpioN/direction
> 
> Do I need to disable the output driver in the IOMUXC or can we just
> disable GPIO_PDDR and use the pin as input?
> 

OBE should also be disabled. Otherwise the input may not function well.

> If we can disable the output driver just using GPIO_PDDR, we can avoid the
> gpio_set_direction cross call.
> 
> 
> >> If not, I really would just not use all that "find pinctrl config"
> >> hackery... e.g. add a new flag, USE_IOMUXC_FOR_GPIO_OUTPUT, and set
> >> that only for Vybrid.
> >>
> >> This would also align much better with the other i.MX devices, where
> >> pinmuxing and GPIO is completely orthogonal.
> >>
> >
> > Actually this patch came only because to make the exist code not break
> > MX7ULP.
> >
> > Actually I'm wondering why we need implement
> > imx_pmx_gpio_request_enable function?
> >
> > Per my understanding, IMX binding already set GPIO mux by Parsing MUX
> > mode from device tree, so why need gpio_request_enable which looks
> > like is duplicated.
> >
> > Can you help explain it?
> 
> I suggest to read this clarification email wrt to pinctrl/gpio from Linus
> Walleij:
> https://lkml.org/lkml/2016/10/10/87
> 
> To summarize: We have different semantics in Vybrid: The GPIO subsystem
> automatically mux the GPIO for you. So in Vybrid, you do not have to mux a
> GPIO (but a valid entry in your device tree is needed, but does not
> assigned to any node).

Okay, Clearer now.

But I do see the users of GPIO pads in Vybrid dts.
Above is an example which make me confuse at first. 

> 
> Is what the driver is doing for Vybrid wrong? It is different from i.MX,
> but afaik, it is not really wrong... Its a valid implementation according
> to the currently defined semantics...  Due to the *need* to touch pinctrl
> for direction, I had to implement cross calls anyway, so I thought I might
> as well go full mile and also mux the GPIO on request...
> 

It's not strickly wrong.
Just a bit confuse that gpio_request_enable seems not quite necessary
As we actually already and must define GPIO mux in device tree according
To standard IMX binding format.
e.g. VF610_PAD_PTB20__GPIO_42 in above sd pad group.
That means pinctrl already does the GPIO mux when enable sd function.

> So the question is, what semantic do we want for i.MX 7ULP? Since it is a
> i.MX device, we probably want the same semantics as i.MX 6/7 is already
> using for the sake of consistency. So in this case the
> gpio_request_enable/disable callbacks are not needed...
> 
> This is how I hope we can do the implementation for i.MX 7ULP:
> - Do not use gpio_request_enable/disable

Yes, we do want that.

> - Do not use gpio_set_direction either

Not, ULP needs it to support GPIO direction switch.

> - Users using a GPIO should enable output driver in IOMUXC (just use a pin
> configuration where output driver is enabled)

Users still need configure OBE/IBE in devicetree for statically assignment.

> - The GPIO driver only enables/disables the output driver using its
> GPIO_PDDR register depending on GPIO direction

No, same reason as the second question.


So, finnaly, I think the solution may be:
1. If Vybrid does not use gpio_request_enable/disable, we can simply
remove it. Both driver keeps using pinctrl gpio_set_direction.

Or.

2. Make gpio_request_enable/disable and gpio_set_direction
As pinctrl-imx core driver callbacks. And only assign gpio_set_direction
For IMX7ULP platform driver while assign both for Vybrid.

Which one would you prefer?

Regards
Dong Aisheng

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Aisheng Dong May 23, 2017, 10:23 a.m. UTC | #5
Hi Stefan,

> -----Original Message-----
> From: A.S. Dong
> Sent: Thursday, May 18, 2017 3:00 PM
> To: 'Stefan Agner'
> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> kernel@pengutronix.de; Alexandre Courbot
> Subject: RE: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
> 
> > -----Original Message-----
> > From: Stefan Agner [mailto:stefan@agner.ch]
> > Sent: Thursday, May 18, 2017 2:16 AM
> > To: A.S. Dong
> > Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> > linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> > kernel@pengutronix.de; Alexandre Courbot
> > Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is
> > gpio
> >
> > On 2017-05-17 00:18, A.S. Dong wrote:
> > >> -----Original Message-----
> > >> From: Stefan Agner [mailto:stefan@agner.ch]
> > >> Sent: Tuesday, May 16, 2017 1:27 AM
> > >> To: A.S. Dong
> > >> Cc: linux-gpio@vger.kernel.org;
> > >> linux-arm-kernel@lists.infradead.org;
> > >> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy
> > >> Duan; kernel@pengutronix.de; Alexandre Courbot
> > >> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0
> > >> is gpio
> > >>
> > >> On 2017-05-14 23:48, Dong Aisheng wrote:
> > >> > Do not assume MUX 0 is GPIO function in core driver as a
> > >> > different SoC may have different value. e.g. MX7ULP Mux 1 is GPIO.
> > >> >
> > >> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > >> > Cc: Alexandre Courbot <gnurou@gmail.com>
> > >> > Cc: Shawn Guo <shawnguo@kernel.org>
> > >> > Cc: Stefan Agner <stefan@agner.ch>
> > >> > Cc: Fugang Duan <fugang.duan@nxp.com>
> > >> > Cc: Bai Ping <ping.bai@nxp.com>
> > >> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> > >> > ---
> > >> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
> > >> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >> >
> > >> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> > >> > b/drivers/pinctrl/freescale/pinctrl-imx.c
> > >> > index 0d6aaca..ed8ea32 100644
> > >> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> > >> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> > >> > @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
> > >> > pinctrl_dev *pctldev,
> > >> >  			continue;
> > >> >  		for (pin = 0; pin < grp->num_pins; pin++) {
> > >> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
> > >> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
> > >> > +			if (imx_pin->pin == offset)
> > >> >  				goto mux_pin;
> > >>
> > >> The reason I added that check was to make sure we pick a mux option
> > >> which is GPIO... With this change, any pinmux might be picked...
> > >>
> > >
> > > First of all, this seems to be wrong to me that GPIO mux mode is SoC
> > > Dependant and should not be put in pinctrl-imx core driver.
> >
> > Hm, agree, we should consider to move
> > imx_pmx_gpio_request_enable/disable_free and
> > imx_pmx_gpio_set_direction into pinctrl-vf610.c
> >
> 
> IMX7ULP may want to use imx_pmx_gpio_set_direction as well to support
> dynamically change GPIO from output to input.
> 
> > >
> > > Secondly, I think we may be over worried and it's not quite
> > > necessary As we did not do the sanity check for both raw config and
> > > mux data read From Device tree, why only do it for GPIO?
> > >
> > > We may trust the data in device tree.
> >
> > In Vybrid, there is no need to explicitly assign a pinmux to use a pin
> > as GPIO. So the pinmux could be anything... The implemented semantics
> > for Vyrbid is really different than i.MX, see below.
> >
> 
> Strange, I do see Vybrid assigning pinmux to GPIO in device tree.
> e.g.
> arch/arm/boot/dts/vf-colibri.dtsi
> pinctrl_esdhc1: esdhc1grp {
>         fsl,pins = <
>                 VF610_PAD_PTA24__ESDHC1_CLK     0x31ef
>                 VF610_PAD_PTA25__ESDHC1_CMD     0x31ef
>                 VF610_PAD_PTA26__ESDHC1_DAT0    0x31ef
>                 VF610_PAD_PTA27__ESDHC1_DAT1    0x31ef
>                 VF610_PAD_PTA28__ESDHC1_DATA2   0x31ef
>                 VF610_PAD_PTA29__ESDHC1_DAT3    0x31ef
>                 VF610_PAD_PTB20__GPIO_42        0x219d
>         >;
> };
> 
> > >
> > >> >  		}
> > >> >  	}
> > >> > @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
> > >> > pinctrl_dev *pctldev,
> > >> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
> > >> >  	reg &= ~info->mux_mask;
> > >> >  	reg |= imx_pin->config;
> > >> > +	reg |= imx_pin->mux_mode << info->mux_shift;
> > >>
> > >> ... and muxed...
> > >>
> > >> Not sure if we want that.
> > >>
> > >> I had to control GPIO output/input through pinctrl since Vybrid
> > >> does not allow to control that from the GPIO block.
> > >>
> > >> However, according to your GPIO patchset, the i.MX 7ULP has a new
> > >> register GPIO_PDDR to control output from the GPIO block. Is
> > >> controlling the output driver from IOMUXC still required?
> > >
> > > Yes, it's still required.
> > >
> >
> > That sounds weird, what is the GPIO_PDDR for then? Sure I  need to
> > enable the output driver to drive the pin, but can I disable output
> > just using GPIO_PDDR?
> 
> No, to fully disable a output, you must disable OBE as well.
> 
> >
> > Maybe we have a miss understanding here:
> >
> > Lets assume we want to switch a GPIO between output and input:
> >
> > echo "output" > /sys/class/gpio/gpioN/direction ..
> > echo "input" > /sys/class/gpio/gpioN/direction
> >
> > Do I need to disable the output driver in the IOMUXC or can we just
> > disable GPIO_PDDR and use the pin as input?
> >
> 
> OBE should also be disabled. Otherwise the input may not function well.
> 
> > If we can disable the output driver just using GPIO_PDDR, we can avoid
> > the gpio_set_direction cross call.
> >
> >
> > >> If not, I really would just not use all that "find pinctrl config"
> > >> hackery... e.g. add a new flag, USE_IOMUXC_FOR_GPIO_OUTPUT, and set
> > >> that only for Vybrid.
> > >>
> > >> This would also align much better with the other i.MX devices,
> > >> where pinmuxing and GPIO is completely orthogonal.
> > >>
> > >
> > > Actually this patch came only because to make the exist code not
> > > break MX7ULP.
> > >
> > > Actually I'm wondering why we need implement
> > > imx_pmx_gpio_request_enable function?
> > >
> > > Per my understanding, IMX binding already set GPIO mux by Parsing
> > > MUX mode from device tree, so why need gpio_request_enable which
> > > looks like is duplicated.
> > >
> > > Can you help explain it?
> >
> > I suggest to read this clarification email wrt to pinctrl/gpio from
> > Linus
> > Walleij:
> > https://lkml.org/lkml/2016/10/10/87
> >
> > To summarize: We have different semantics in Vybrid: The GPIO
> > subsystem automatically mux the GPIO for you. So in Vybrid, you do not
> > have to mux a GPIO (but a valid entry in your device tree is needed,
> > but does not assigned to any node).
> 
> Okay, Clearer now.
> 
> But I do see the users of GPIO pads in Vybrid dts.
> Above is an example which make me confuse at first.
> 
> >
> > Is what the driver is doing for Vybrid wrong? It is different from
> > i.MX, but afaik, it is not really wrong... Its a valid implementation
> > according to the currently defined semantics...  Due to the *need* to
> > touch pinctrl for direction, I had to implement cross calls anyway, so
> > I thought I might as well go full mile and also mux the GPIO on
> request...
> >
> 
> It's not strickly wrong.
> Just a bit confuse that gpio_request_enable seems not quite necessary As
> we actually already and must define GPIO mux in device tree according To
> standard IMX binding format.
> e.g. VF610_PAD_PTB20__GPIO_42 in above sd pad group.
> That means pinctrl already does the GPIO mux when enable sd function.
> 
> > So the question is, what semantic do we want for i.MX 7ULP? Since it
> > is a i.MX device, we probably want the same semantics as i.MX 6/7 is
> > already using for the sake of consistency. So in this case the
> > gpio_request_enable/disable callbacks are not needed...
> >
> > This is how I hope we can do the implementation for i.MX 7ULP:
> > - Do not use gpio_request_enable/disable
> 
> Yes, we do want that.
> 
> > - Do not use gpio_set_direction either
> 
> Not, ULP needs it to support GPIO direction switch.
> 
> > - Users using a GPIO should enable output driver in IOMUXC (just use a
> > pin configuration where output driver is enabled)
> 
> Users still need configure OBE/IBE in devicetree for statically assignment.
> 
> > - The GPIO driver only enables/disables the output driver using its
> > GPIO_PDDR register depending on GPIO direction
> 
> No, same reason as the second question.
> 
> 
> So, finnaly, I think the solution may be:
> 1. If Vybrid does not use gpio_request_enable/disable, we can simply
> remove it. Both driver keeps using pinctrl gpio_set_direction.
> 
> Or.
> 
> 2. Make gpio_request_enable/disable and gpio_set_direction As pinctrl-imx
> core driver callbacks. And only assign gpio_set_direction For IMX7ULP
> platform driver while assign both for Vybrid.
> 
> Which one would you prefer?
> 

Any answer about it?

Regards
Dong Aisheng
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Stefan Agner May 23, 2017, 7:55 p.m. UTC | #6
On 2017-05-23 03:23, A.S. Dong wrote:
> Hi Stefan,
> 
>> -----Original Message-----
>> From: A.S. Dong
>> Sent: Thursday, May 18, 2017 3:00 PM
>> To: 'Stefan Agner'
>> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
>> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
>> kernel@pengutronix.de; Alexandre Courbot
>> Subject: RE: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
>>
>> > -----Original Message-----
>> > From: Stefan Agner [mailto:stefan@agner.ch]
>> > Sent: Thursday, May 18, 2017 2:16 AM
>> > To: A.S. Dong
>> > Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
>> > linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
>> > kernel@pengutronix.de; Alexandre Courbot
>> > Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is
>> > gpio
>> >
>> > On 2017-05-17 00:18, A.S. Dong wrote:
>> > >> -----Original Message-----
>> > >> From: Stefan Agner [mailto:stefan@agner.ch]
>> > >> Sent: Tuesday, May 16, 2017 1:27 AM
>> > >> To: A.S. Dong
>> > >> Cc: linux-gpio@vger.kernel.org;
>> > >> linux-arm-kernel@lists.infradead.org;
>> > >> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy
>> > >> Duan; kernel@pengutronix.de; Alexandre Courbot
>> > >> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0
>> > >> is gpio
>> > >>
>> > >> On 2017-05-14 23:48, Dong Aisheng wrote:
>> > >> > Do not assume MUX 0 is GPIO function in core driver as a
>> > >> > different SoC may have different value. e.g. MX7ULP Mux 1 is GPIO.
>> > >> >
>> > >> > Cc: Linus Walleij <linus.walleij@linaro.org>
>> > >> > Cc: Alexandre Courbot <gnurou@gmail.com>
>> > >> > Cc: Shawn Guo <shawnguo@kernel.org>
>> > >> > Cc: Stefan Agner <stefan@agner.ch>
>> > >> > Cc: Fugang Duan <fugang.duan@nxp.com>
>> > >> > Cc: Bai Ping <ping.bai@nxp.com>
>> > >> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
>> > >> > ---
>> > >> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
>> > >> >  1 file changed, 2 insertions(+), 1 deletion(-)
>> > >> >
>> > >> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
>> > >> > b/drivers/pinctrl/freescale/pinctrl-imx.c
>> > >> > index 0d6aaca..ed8ea32 100644
>> > >> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
>> > >> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
>> > >> > @@ -281,7 +281,7 @@ static int imx_pmx_gpio_request_enable(struct
>> > >> > pinctrl_dev *pctldev,
>> > >> >  			continue;
>> > >> >  		for (pin = 0; pin < grp->num_pins; pin++) {
>> > >> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
>> > >> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
>> > >> > +			if (imx_pin->pin == offset)
>> > >> >  				goto mux_pin;
>> > >>
>> > >> The reason I added that check was to make sure we pick a mux option
>> > >> which is GPIO... With this change, any pinmux might be picked...
>> > >>
>> > >
>> > > First of all, this seems to be wrong to me that GPIO mux mode is SoC
>> > > Dependant and should not be put in pinctrl-imx core driver.
>> >
>> > Hm, agree, we should consider to move
>> > imx_pmx_gpio_request_enable/disable_free and
>> > imx_pmx_gpio_set_direction into pinctrl-vf610.c
>> >
>>
>> IMX7ULP may want to use imx_pmx_gpio_set_direction as well to support
>> dynamically change GPIO from output to input.
>>
>> > >
>> > > Secondly, I think we may be over worried and it's not quite
>> > > necessary As we did not do the sanity check for both raw config and
>> > > mux data read From Device tree, why only do it for GPIO?
>> > >
>> > > We may trust the data in device tree.
>> >
>> > In Vybrid, there is no need to explicitly assign a pinmux to use a pin
>> > as GPIO. So the pinmux could be anything... The implemented semantics
>> > for Vyrbid is really different than i.MX, see below.
>> >
>>
>> Strange, I do see Vybrid assigning pinmux to GPIO in device tree.
>> e.g.
>> arch/arm/boot/dts/vf-colibri.dtsi
>> pinctrl_esdhc1: esdhc1grp {
>>         fsl,pins = <
>>                 VF610_PAD_PTA24__ESDHC1_CLK     0x31ef
>>                 VF610_PAD_PTA25__ESDHC1_CMD     0x31ef
>>                 VF610_PAD_PTA26__ESDHC1_DAT0    0x31ef
>>                 VF610_PAD_PTA27__ESDHC1_DAT1    0x31ef
>>                 VF610_PAD_PTA28__ESDHC1_DATA2   0x31ef
>>                 VF610_PAD_PTA29__ESDHC1_DAT3    0x31ef
>>                 VF610_PAD_PTB20__GPIO_42        0x219d
>>         >;
>> };
>>
>> > >
>> > >> >  		}
>> > >> >  	}
>> > >> > @@ -292,6 +292,7 @@ static int imx_pmx_gpio_request_enable(struct
>> > >> > pinctrl_dev *pctldev,
>> > >> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
>> > >> >  	reg &= ~info->mux_mask;
>> > >> >  	reg |= imx_pin->config;
>> > >> > +	reg |= imx_pin->mux_mode << info->mux_shift;
>> > >>
>> > >> ... and muxed...
>> > >>
>> > >> Not sure if we want that.
>> > >>
>> > >> I had to control GPIO output/input through pinctrl since Vybrid
>> > >> does not allow to control that from the GPIO block.
>> > >>
>> > >> However, according to your GPIO patchset, the i.MX 7ULP has a new
>> > >> register GPIO_PDDR to control output from the GPIO block. Is
>> > >> controlling the output driver from IOMUXC still required?
>> > >
>> > > Yes, it's still required.
>> > >
>> >
>> > That sounds weird, what is the GPIO_PDDR for then? Sure I  need to
>> > enable the output driver to drive the pin, but can I disable output
>> > just using GPIO_PDDR?
>>
>> No, to fully disable a output, you must disable OBE as well.
>>
>> >
>> > Maybe we have a miss understanding here:
>> >
>> > Lets assume we want to switch a GPIO between output and input:
>> >
>> > echo "output" > /sys/class/gpio/gpioN/direction ..
>> > echo "input" > /sys/class/gpio/gpioN/direction
>> >
>> > Do I need to disable the output driver in the IOMUXC or can we just
>> > disable GPIO_PDDR and use the pin as input?
>> >
>>
>> OBE should also be disabled. Otherwise the input may not function well.
>>
>> > If we can disable the output driver just using GPIO_PDDR, we can avoid
>> > the gpio_set_direction cross call.
>> >
>> >
>> > >> If not, I really would just not use all that "find pinctrl config"
>> > >> hackery... e.g. add a new flag, USE_IOMUXC_FOR_GPIO_OUTPUT, and set
>> > >> that only for Vybrid.
>> > >>
>> > >> This would also align much better with the other i.MX devices,
>> > >> where pinmuxing and GPIO is completely orthogonal.
>> > >>
>> > >
>> > > Actually this patch came only because to make the exist code not
>> > > break MX7ULP.
>> > >
>> > > Actually I'm wondering why we need implement
>> > > imx_pmx_gpio_request_enable function?
>> > >
>> > > Per my understanding, IMX binding already set GPIO mux by Parsing
>> > > MUX mode from device tree, so why need gpio_request_enable which
>> > > looks like is duplicated.
>> > >
>> > > Can you help explain it?
>> >
>> > I suggest to read this clarification email wrt to pinctrl/gpio from
>> > Linus
>> > Walleij:
>> > https://lkml.org/lkml/2016/10/10/87
>> >
>> > To summarize: We have different semantics in Vybrid: The GPIO
>> > subsystem automatically mux the GPIO for you. So in Vybrid, you do not
>> > have to mux a GPIO (but a valid entry in your device tree is needed,
>> > but does not assigned to any node).
>>
>> Okay, Clearer now.
>>
>> But I do see the users of GPIO pads in Vybrid dts.
>> Above is an example which make me confuse at first.
>>
>> >
>> > Is what the driver is doing for Vybrid wrong? It is different from
>> > i.MX, but afaik, it is not really wrong... Its a valid implementation
>> > according to the currently defined semantics...  Due to the *need* to
>> > touch pinctrl for direction, I had to implement cross calls anyway, so
>> > I thought I might as well go full mile and also mux the GPIO on
>> request...
>> >
>>
>> It's not strickly wrong.
>> Just a bit confuse that gpio_request_enable seems not quite necessary As
>> we actually already and must define GPIO mux in device tree according To
>> standard IMX binding format.
>> e.g. VF610_PAD_PTB20__GPIO_42 in above sd pad group.
>> That means pinctrl already does the GPIO mux when enable sd function.
>>
>> > So the question is, what semantic do we want for i.MX 7ULP? Since it
>> > is a i.MX device, we probably want the same semantics as i.MX 6/7 is
>> > already using for the sake of consistency. So in this case the
>> > gpio_request_enable/disable callbacks are not needed...
>> >
>> > This is how I hope we can do the implementation for i.MX 7ULP:
>> > - Do not use gpio_request_enable/disable
>>
>> Yes, we do want that.
>>
>> > - Do not use gpio_set_direction either
>>
>> Not, ULP needs it to support GPIO direction switch.
>>
>> > - Users using a GPIO should enable output driver in IOMUXC (just use a
>> > pin configuration where output driver is enabled)
>>
>> Users still need configure OBE/IBE in devicetree for statically assignment.
>>
>> > - The GPIO driver only enables/disables the output driver using its
>> > GPIO_PDDR register depending on GPIO direction
>>
>> No, same reason as the second question.
>>
>>
>> So, finnaly, I think the solution may be:
>> 1. If Vybrid does not use gpio_request_enable/disable, we can simply
>> remove it. Both driver keeps using pinctrl gpio_set_direction.
>>
>> Or.
>>
>> 2. Make gpio_request_enable/disable and gpio_set_direction As pinctrl-imx
>> core driver callbacks. And only assign gpio_set_direction For IMX7ULP
>> platform driver while assign both for Vybrid.
>>
>> Which one would you prefer?

1 would mean a semantic change.

For all GPIO I checked in upstream device trees we assign a pinctrl to
the same node, so in all cases gpio_request_enable/disable is really
unnecessary.

And since the current implementation has adversarial effects for I2C
recovery (https://patchwork.kernel.org/patch/9351401/), we use the
orthogonal semantic in the closely related i.MX SoCs and it even
simplifies the driver, I am ok to change the semantic.

Can you prepare such a patchset so that we can further test that on
Vybrid?

--
Stefan
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Aisheng Dong May 24, 2017, 5:40 a.m. UTC | #7
> -----Original Message-----
> From: Stefan Agner [mailto:stefan@agner.ch]
> Sent: Wednesday, May 24, 2017 3:55 AM
> To: A.S. Dong
> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> kernel@pengutronix.de; Alexandre Courbot
> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is gpio
> 
> On 2017-05-23 03:23, A.S. Dong wrote:
> > Hi Stefan,
> >
> >> -----Original Message-----
> >> From: A.S. Dong
> >> Sent: Thursday, May 18, 2017 3:00 PM
> >> To: 'Stefan Agner'
> >> Cc: linux-gpio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> >> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy Duan;
> >> kernel@pengutronix.de; Alexandre Courbot
> >> Subject: RE: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0 is
> >> gpio
> >>
> >> > -----Original Message-----
> >> > From: Stefan Agner [mailto:stefan@agner.ch]
> >> > Sent: Thursday, May 18, 2017 2:16 AM
> >> > To: A.S. Dong
> >> > Cc: linux-gpio@vger.kernel.org;
> >> > linux-arm-kernel@lists.infradead.org;
> >> > linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy
> >> > Duan; kernel@pengutronix.de; Alexandre Courbot
> >> > Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux 0
> >> > is gpio
> >> >
> >> > On 2017-05-17 00:18, A.S. Dong wrote:
> >> > >> -----Original Message-----
> >> > >> From: Stefan Agner [mailto:stefan@agner.ch]
> >> > >> Sent: Tuesday, May 16, 2017 1:27 AM
> >> > >> To: A.S. Dong
> >> > >> Cc: linux-gpio@vger.kernel.org;
> >> > >> linux-arm-kernel@lists.infradead.org;
> >> > >> linus.walleij@linaro.org; shawnguo@kernel.org; Jacky Bai; Andy
> >> > >> Duan; kernel@pengutronix.de; Alexandre Courbot
> >> > >> Subject: Re: [PATCH 2/2] pinctrl: pinctrl-imx: do not assume mux
> >> > >> 0 is gpio
> >> > >>
> >> > >> On 2017-05-14 23:48, Dong Aisheng wrote:
> >> > >> > Do not assume MUX 0 is GPIO function in core driver as a
> >> > >> > different SoC may have different value. e.g. MX7ULP Mux 1 is
> GPIO.
> >> > >> >
> >> > >> > Cc: Linus Walleij <linus.walleij@linaro.org>
> >> > >> > Cc: Alexandre Courbot <gnurou@gmail.com>
> >> > >> > Cc: Shawn Guo <shawnguo@kernel.org>
> >> > >> > Cc: Stefan Agner <stefan@agner.ch>
> >> > >> > Cc: Fugang Duan <fugang.duan@nxp.com>
> >> > >> > Cc: Bai Ping <ping.bai@nxp.com>
> >> > >> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> >> > >> > ---
> >> > >> >  drivers/pinctrl/freescale/pinctrl-imx.c | 3 ++-
> >> > >> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >> > >> >
> >> > >> > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > >> > b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > >> > index 0d6aaca..ed8ea32 100644
> >> > >> > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > >> > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > >> > @@ -281,7 +281,7 @@ static int
> >> > >> > imx_pmx_gpio_request_enable(struct
> >> > >> > pinctrl_dev *pctldev,
> >> > >> >  			continue;
> >> > >> >  		for (pin = 0; pin < grp->num_pins; pin++) {
> >> > >> >  			imx_pin = &((struct imx_pin *)(grp->data))[pin];
> >> > >> > -			if (imx_pin->pin == offset && !imx_pin->mux_mode)
> >> > >> > +			if (imx_pin->pin == offset)
> >> > >> >  				goto mux_pin;
> >> > >>
> >> > >> The reason I added that check was to make sure we pick a mux
> >> > >> option which is GPIO... With this change, any pinmux might be
> picked...
> >> > >>
> >> > >
> >> > > First of all, this seems to be wrong to me that GPIO mux mode is
> >> > > SoC Dependant and should not be put in pinctrl-imx core driver.
> >> >
> >> > Hm, agree, we should consider to move
> >> > imx_pmx_gpio_request_enable/disable_free and
> >> > imx_pmx_gpio_set_direction into pinctrl-vf610.c
> >> >
> >>
> >> IMX7ULP may want to use imx_pmx_gpio_set_direction as well to support
> >> dynamically change GPIO from output to input.
> >>
> >> > >
> >> > > Secondly, I think we may be over worried and it's not quite
> >> > > necessary As we did not do the sanity check for both raw config
> >> > > and mux data read From Device tree, why only do it for GPIO?
> >> > >
> >> > > We may trust the data in device tree.
> >> >
> >> > In Vybrid, there is no need to explicitly assign a pinmux to use a
> >> > pin as GPIO. So the pinmux could be anything... The implemented
> >> > semantics for Vyrbid is really different than i.MX, see below.
> >> >
> >>
> >> Strange, I do see Vybrid assigning pinmux to GPIO in device tree.
> >> e.g.
> >> arch/arm/boot/dts/vf-colibri.dtsi
> >> pinctrl_esdhc1: esdhc1grp {
> >>         fsl,pins = <
> >>                 VF610_PAD_PTA24__ESDHC1_CLK     0x31ef
> >>                 VF610_PAD_PTA25__ESDHC1_CMD     0x31ef
> >>                 VF610_PAD_PTA26__ESDHC1_DAT0    0x31ef
> >>                 VF610_PAD_PTA27__ESDHC1_DAT1    0x31ef
> >>                 VF610_PAD_PTA28__ESDHC1_DATA2   0x31ef
> >>                 VF610_PAD_PTA29__ESDHC1_DAT3    0x31ef
> >>                 VF610_PAD_PTB20__GPIO_42        0x219d
> >>         >;
> >> };
> >>
> >> > >
> >> > >> >  		}
> >> > >> >  	}
> >> > >> > @@ -292,6 +292,7 @@ static int
> >> > >> > imx_pmx_gpio_request_enable(struct
> >> > >> > pinctrl_dev *pctldev,
> >> > >> >  	reg = readl(ipctl->base + pin_reg->mux_reg);
> >> > >> >  	reg &= ~info->mux_mask;
> >> > >> >  	reg |= imx_pin->config;
> >> > >> > +	reg |= imx_pin->mux_mode << info->mux_shift;
> >> > >>
> >> > >> ... and muxed...
> >> > >>
> >> > >> Not sure if we want that.
> >> > >>
> >> > >> I had to control GPIO output/input through pinctrl since Vybrid
> >> > >> does not allow to control that from the GPIO block.
> >> > >>
> >> > >> However, according to your GPIO patchset, the i.MX 7ULP has a
> >> > >> new register GPIO_PDDR to control output from the GPIO block. Is
> >> > >> controlling the output driver from IOMUXC still required?
> >> > >
> >> > > Yes, it's still required.
> >> > >
> >> >
> >> > That sounds weird, what is the GPIO_PDDR for then? Sure I  need to
> >> > enable the output driver to drive the pin, but can I disable output
> >> > just using GPIO_PDDR?
> >>
> >> No, to fully disable a output, you must disable OBE as well.
> >>
> >> >
> >> > Maybe we have a miss understanding here:
> >> >
> >> > Lets assume we want to switch a GPIO between output and input:
> >> >
> >> > echo "output" > /sys/class/gpio/gpioN/direction ..
> >> > echo "input" > /sys/class/gpio/gpioN/direction
> >> >
> >> > Do I need to disable the output driver in the IOMUXC or can we just
> >> > disable GPIO_PDDR and use the pin as input?
> >> >
> >>
> >> OBE should also be disabled. Otherwise the input may not function well.
> >>
> >> > If we can disable the output driver just using GPIO_PDDR, we can
> >> > avoid the gpio_set_direction cross call.
> >> >
> >> >
> >> > >> If not, I really would just not use all that "find pinctrl config"
> >> > >> hackery... e.g. add a new flag, USE_IOMUXC_FOR_GPIO_OUTPUT, and
> >> > >> set that only for Vybrid.
> >> > >>
> >> > >> This would also align much better with the other i.MX devices,
> >> > >> where pinmuxing and GPIO is completely orthogonal.
> >> > >>
> >> > >
> >> > > Actually this patch came only because to make the exist code not
> >> > > break MX7ULP.
> >> > >
> >> > > Actually I'm wondering why we need implement
> >> > > imx_pmx_gpio_request_enable function?
> >> > >
> >> > > Per my understanding, IMX binding already set GPIO mux by Parsing
> >> > > MUX mode from device tree, so why need gpio_request_enable which
> >> > > looks like is duplicated.
> >> > >
> >> > > Can you help explain it?
> >> >
> >> > I suggest to read this clarification email wrt to pinctrl/gpio from
> >> > Linus
> >> > Walleij:
> >> > https://lkml.org/lkml/2016/10/10/87
> >> >
> >> > To summarize: We have different semantics in Vybrid: The GPIO
> >> > subsystem automatically mux the GPIO for you. So in Vybrid, you do
> >> > not have to mux a GPIO (but a valid entry in your device tree is
> >> > needed, but does not assigned to any node).
> >>
> >> Okay, Clearer now.
> >>
> >> But I do see the users of GPIO pads in Vybrid dts.
> >> Above is an example which make me confuse at first.
> >>
> >> >
> >> > Is what the driver is doing for Vybrid wrong? It is different from
> >> > i.MX, but afaik, it is not really wrong... Its a valid
> >> > implementation according to the currently defined semantics...  Due
> >> > to the *need* to touch pinctrl for direction, I had to implement
> >> > cross calls anyway, so I thought I might as well go full mile and
> >> > also mux the GPIO on
> >> request...
> >> >
> >>
> >> It's not strickly wrong.
> >> Just a bit confuse that gpio_request_enable seems not quite necessary
> >> As we actually already and must define GPIO mux in device tree
> >> according To standard IMX binding format.
> >> e.g. VF610_PAD_PTB20__GPIO_42 in above sd pad group.
> >> That means pinctrl already does the GPIO mux when enable sd function.
> >>
> >> > So the question is, what semantic do we want for i.MX 7ULP? Since
> >> > it is a i.MX device, we probably want the same semantics as i.MX
> >> > 6/7 is already using for the sake of consistency. So in this case
> >> > the gpio_request_enable/disable callbacks are not needed...
> >> >
> >> > This is how I hope we can do the implementation for i.MX 7ULP:
> >> > - Do not use gpio_request_enable/disable
> >>
> >> Yes, we do want that.
> >>
> >> > - Do not use gpio_set_direction either
> >>
> >> Not, ULP needs it to support GPIO direction switch.
> >>
> >> > - Users using a GPIO should enable output driver in IOMUXC (just
> >> > use a pin configuration where output driver is enabled)
> >>
> >> Users still need configure OBE/IBE in devicetree for statically
> assignment.
> >>
> >> > - The GPIO driver only enables/disables the output driver using its
> >> > GPIO_PDDR register depending on GPIO direction
> >>
> >> No, same reason as the second question.
> >>
> >>
> >> So, finnaly, I think the solution may be:
> >> 1. If Vybrid does not use gpio_request_enable/disable, we can simply
> >> remove it. Both driver keeps using pinctrl gpio_set_direction.
> >>
> >> Or.
> >>
> >> 2. Make gpio_request_enable/disable and gpio_set_direction As
> >> pinctrl-imx core driver callbacks. And only assign gpio_set_direction
> >> For IMX7ULP platform driver while assign both for Vybrid.
> >>
> >> Which one would you prefer?
> 
> 1 would mean a semantic change.
> 
> For all GPIO I checked in upstream device trees we assign a pinctrl to the
> same node, so in all cases gpio_request_enable/disable is really
> unnecessary.
> 
> And since the current implementation has adversarial effects for I2C
> recovery (https://patchwork.kernel.org/patch/9351401/), we use the
> orthogonal semantic in the closely related i.MX SoCs and it even
> simplifies the driver, I am ok to change the semantic.
> 

I checked the I2C recovery issue you mentioned above, it looks
Changing the semantic as I proposed may fix it as well.

> Can you prepare such a patchset so that we can further test that on Vybrid?
> 

I will prepare it.

Thanks

Regards
Dong Aisheng
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Patch
diff mbox

diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c b/drivers/pinctrl/freescale/pinctrl-imx.c
index 0d6aaca..ed8ea32 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.c
+++ b/drivers/pinctrl/freescale/pinctrl-imx.c
@@ -281,7 +281,7 @@  static int imx_pmx_gpio_request_enable(struct pinctrl_dev *pctldev,
 			continue;
 		for (pin = 0; pin < grp->num_pins; pin++) {
 			imx_pin = &((struct imx_pin *)(grp->data))[pin];
-			if (imx_pin->pin == offset && !imx_pin->mux_mode)
+			if (imx_pin->pin == offset)
 				goto mux_pin;
 		}
 	}
@@ -292,6 +292,7 @@  static int imx_pmx_gpio_request_enable(struct pinctrl_dev *pctldev,
 	reg = readl(ipctl->base + pin_reg->mux_reg);
 	reg &= ~info->mux_mask;
 	reg |= imx_pin->config;
+	reg |= imx_pin->mux_mode << info->mux_shift;
 	writel(reg, ipctl->base + pin_reg->mux_reg);
 
 	return 0;