RE: [PATCH 1/2] pinctrl: pinctrl-imx: add IBE and OBE SoC property

["A.S. Dong" <aisheng.dong@xxxxxxx>]

Hi Stefan,

> -----Original Message-----
> From: Stefan Agner [mailto:stefan@xxxxxxxx]
> Sent: Wednesday, May 24, 2017 3:16 AM
> To: A.S. Dong
> Cc: linux-gpio@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linus.walleij@xxxxxxxxxx; shawnguo@xxxxxxxxxx; Jacky Bai; Andy Duan;
> kernel@xxxxxxxxxxxxxx; Alexandre Courbot
> Subject: Re: [PATCH 1/2] pinctrl: pinctrl-imx: add IBE and OBE SoC
> property
> 
> On 2017-05-23 05:06, A.S. Dong wrote:
> > Hi Stefan,
> >
> >> -----Original Message-----
> >> From: A.S. Dong
> >> Sent: Wednesday, May 17, 2017 2:14 PM
> >> To: 'Stefan Agner'
> >> Cc: linux-gpio@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> >> linus.walleij@xxxxxxxxxx; shawnguo@xxxxxxxxxx; Jacky Bai; Andy Duan;
> >> kernel@xxxxxxxxxxxxxx; Alexandre Courbot
> >> Subject: RE: [PATCH 1/2] pinctrl: pinctrl-imx: add IBE and OBE SoC
> >> property
> >>
> >> > -----Original Message-----
> >> > From: Stefan Agner [mailto:stefan@xxxxxxxx]
> >> > Sent: Tuesday, May 16, 2017 1:11 AM
> >> > To: A.S. Dong
> >> > Cc: linux-gpio@xxxxxxxxxxxxxxx;
> >> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> >> > linus.walleij@xxxxxxxxxx; shawnguo@xxxxxxxxxx; Jacky Bai; Andy
> >> > Duan; kernel@xxxxxxxxxxxxxx; Alexandre Courbot
> >> > Subject: Re: [PATCH 1/2] pinctrl: pinctrl-imx: add IBE and OBE SoC
> >> > property
> >> >
> >> > On 2017-05-14 23:48, Dong Aisheng wrote:
> >> > > iMX ULP has different IOB/OBE shift from Vibrid, so let's make
> >> >
> >> > s/Vibrid/Vybrid
> >> >
> >> > > it a SoC property.
> >> > >
> >> > > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> >> > > Cc: Alexandre Courbot <gnurou@xxxxxxxxx>
> >> > > Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
> >> > > Cc: Stefan Agner <stefan@xxxxxxxx>
> >> > > Cc: Fugang Duan <fugang.duan@xxxxxxx>
> >> > > Cc: Bai Ping <ping.bai@xxxxxxx>
> >> > > Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
> >> > > ---
> >> > >  drivers/pinctrl/freescale/pinctrl-imx.c     | 8 ++++----
> >> > >  drivers/pinctrl/freescale/pinctrl-imx.h     | 2 ++
> >> > >  drivers/pinctrl/freescale/pinctrl-imx7ulp.c | 2 ++
> >> > >  drivers/pinctrl/freescale/pinctrl-vf610.c   | 2 ++
> >> > >  4 files changed, 10 insertions(+), 4 deletions(-)
> >> > >
> >> > > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > > b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > > index 57e1f7a..0d6aaca 100644
> >> > > --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > > +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> >> > > @@ -331,8 +331,8 @@ static int imx_pmx_gpio_set_direction(struct
> >> > > pinctrl_dev *pctldev,
> >> > >  	u32 reg;
> >> > >
> >> > >  	/*
> >> > > -	 * Only Vybrid has the input/output buffer enable flags
> (IBE/OBE)
> >> > > -	 * They are part of the shared mux/conf register.
> >> > > +	 * Only Vybrid and iMX ULP has the input/output buffer enable
> flags
> >> > > +	 * (IBE/OBE) They are part of the shared mux/conf register.
> >> > >  	 */
> >> > >  	if (!(info->flags & SHARE_MUX_CONF_REG))
> >> > >  		return 0;
> >> > > @@ -344,9 +344,9 @@ static int imx_pmx_gpio_set_direction(struct
> >> > > pinctrl_dev *pctldev,
> >> > >  	/* IBE always enabled allows us to read the value "on the
> wire" */
> >> > >  	reg = readl(ipctl->base + pin_reg->mux_reg);
> >> > >  	if (input)
> >> > > -		reg &= ~0x2;
> >> > > +		reg = (reg & ~info->obe_bit) | info->ibe_bit;
> >> > >  	else
> >> > > -		reg |= 0x2;
> >> > > +		reg = (reg & ~info->ibe_bit) | info->obe_bit;
> >> >
> >> > Why disabling IBE bit now? As the comment above states, it is
> >> > really handy to leave the input buffer enabled so we can read back
> >> > the true value on the wire...
> >> >
> >>
> >> Does Vybrid reply on this bit to read the status of output from Port
> >> Data Input Register (GPIOx_PDIR)?
> >>
> >> Then, it is a bit strange that read status from input register when
> >> the GPIO is Actually configured as output.
> >>
> >> Probably it works on Vybrid, but I don't know if it's valid for MX7ULP.
> >>
> >> For MX7ULP, we will read input or output register accordingly by
> >> checking GPIO direction register (PDDR) and we will not enable Input
> >> buffer if the GPIO is configured as output, this also save a bit power.
> >>
> >> I know Vybrid has no PDDR, probably that's why you enable IBE by
> >> default always.
> >>
> 
> The main reason I enable input buffer by default is so that software has a
> chance to see the actual state of the GPIO. E.g. when a GPIO is connected
> to GND, and you set it high, you can read back a 0... (of course you
> should not connect a GPIO to GND and set it high! But that is exactly the
> point, with enabling the input buffer you actually see that something is
> wrong!)
> 
> Can we not do this for iMX7ULP too?
> 

Hmm.. I probably would think it reversely.
For me, I'd prefer the gpio value read back reflect the real value set in
GPIO controller, not the actual state on the line.
It at least tells "Hey, your GPIO SW setting is okay, check HW ..".

Users could measure the actual state if something is wrong.

> >
> > We need make a decision on how to address the difference between
> > Vybrid And IMX7ULP.
> >
> > If Vybrid wants to keep input buffer enabled, we probably could invent
> > A IMX_PINCONF_HAVE_PDDR just like GPIO driver and only disable IBE for
> IMX?
> 
> That would be one option yes. You also need a flag so you can opt out from
> imx_pmx_gpio_enable/disable_free...
> 
> The more involved version would be to somehow move imx_pmx_gpio_* to
> pinctrl-vf610.c, e.g. store the callbacks in imx_pinctrl_soc_info and set
> them dynamically in imx_pinctrl_probe (you have to unconst pinmux_ops).
> With that you can provide no imx_pmx_gpio_enable/disable_free for iMX7ULP
> and your own imx_pmx_gpio_set_direction...
> 

Since we've got an agreement to remove gpio_enable/disable_free in another
mail I just replied, I will remove it and only keep gpio_set_direction,
but re-implement it as platform specific callback API.

Regards
Dong Aisheng

> --
> Stefan
> 
> >
> > Do you think it's ok?
> >
> >
> > Regards
> > Dong Aisheng
> >
> >
> >> Regards
> >> Dong Aisheng
> >>
> >> > --
> >> > Stefan
> >> >
> >> > >  	writel(reg, ipctl->base + pin_reg->mux_reg);
> >> > >
> >> > >  	return 0;
> >> > > diff --git a/drivers/pinctrl/freescale/pinctrl-imx.h
> >> > > b/drivers/pinctrl/freescale/pinctrl-imx.h
> >> > > index eb0ce95..9ded65d 100644
> >> > > --- a/drivers/pinctrl/freescale/pinctrl-imx.h
> >> > > +++ b/drivers/pinctrl/freescale/pinctrl-imx.h
> >> > > @@ -67,6 +67,8 @@ struct imx_pinctrl_soc_info {
> >> > >  	/* MUX_MODE shift and mask in case SHARE_MUX_CONF_REG */
> >> > >  	unsigned int mux_mask;
> >> > >  	u8 mux_shift;
> >> > > +	u32 ibe_bit;
> >> > > +	u32 obe_bit;
> >> > >
> >> > >  	/* generic pinconf */
> >> > >  	bool generic_pinconf;
> >> > > diff --git a/drivers/pinctrl/freescale/pinctrl-imx7ulp.c
> >> > > b/drivers/pinctrl/freescale/pinctrl-imx7ulp.c
> >> > > index dead416..f724a01 100644
> >> > > --- a/drivers/pinctrl/freescale/pinctrl-imx7ulp.c
> >> > > +++ b/drivers/pinctrl/freescale/pinctrl-imx7ulp.c
> >> > > @@ -324,6 +324,8 @@ static struct imx_pinctrl_soc_info
> >> > imx7ulp_pinctrl_info = {
> >> > >  	.flags = ZERO_OFFSET_VALID | SHARE_MUX_CONF_REG,
> >> > >  	.mux_mask = 0xf00,
> >> > >  	.mux_shift = 8,
> >> > > +	.ibe_bit = BIT(16),
> >> > > +	.obe_bit = BIT(17),
> >> > >  	.generic_pinconf = true,
> >> > >  	.custom_params = imx7ulp_cfg_params,
> >> > >  	.num_custom_params = ARRAY_SIZE(imx7ulp_cfg_params), diff --
> git
> >> > > a/drivers/pinctrl/freescale/pinctrl-vf610.c
> >> > > b/drivers/pinctrl/freescale/pinctrl-vf610.c
> >> > > index 3bd8556..c0823f9 100644
> >> > > --- a/drivers/pinctrl/freescale/pinctrl-vf610.c
> >> > > +++ b/drivers/pinctrl/freescale/pinctrl-vf610.c
> >> > > @@ -301,6 +301,8 @@ static struct imx_pinctrl_soc_info
> >> > vf610_pinctrl_info = {
> >> > >  	.flags = SHARE_MUX_CONF_REG | ZERO_OFFSET_VALID,
> >> > >  	.mux_mask = 0x700000,
> >> > >  	.mux_shift = 20,
> >> > > +	.ibe_bit = BIT(0),
> >> > > +	.obe_bit = BIT(1),
> >> > >  };
> >> > >
> >> > >  static const struct of_device_id vf610_pinctrl_of_match[] = {
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