Re: [PATCH v2 2/5] pinctrl: imx: add gpio pinmux support for vf610

[Shawn Guo <shawn.guo@freescale.com>]

On Thu, Sep 25, 2014 at 09:00:41AM +0200, Stefan Agner wrote:
> Am 2014-09-25 04:47, schrieb Shawn Guo:
> > On Tue, Sep 23, 2014 at 07:37:54PM +0200, Stefan Agner wrote:
> >> Add pinmux support for GPIO for Vybrid (vf610) IOMUX controller.
> >> This is needed since direction configuration is not part of the
> >> GPIO module in Vybrid.
> >>
> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
> >> ---
> >>  drivers/pinctrl/pinctrl-imx.c   | 54 +++++++++++++++++++++++++++++++++++++++++
> >>  drivers/pinctrl/pinctrl-imx.h   |  1 +
> >>  drivers/pinctrl/pinctrl-vf610.c |  2 +-
> >>  3 files changed, 56 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/pinctrl/pinctrl-imx.c b/drivers/pinctrl/pinctrl-imx.c
> >> index 0d4558b..64d1b59 100644
> >> --- a/drivers/pinctrl/pinctrl-imx.c
> >> +++ b/drivers/pinctrl/pinctrl-imx.c
> >> @@ -294,10 +294,59 @@ static int imx_pmx_get_groups(struct pinctrl_dev *pctldev, unsigned selector,
> >>  	return 0;
> >>  }
> >>
> >> +static int imx_pmx_gpio_request_enable(struct pinctrl_dev *pctldev,
> >> +			struct pinctrl_gpio_range *range, unsigned offset)
> >> +{
> >> +	struct imx_pinctrl *ipctl = pinctrl_dev_get_drvdata(pctldev);
> >> +	const struct imx_pinctrl_soc_info *info = ipctl->info;
> >> +	const struct imx_pin_reg *pin_reg;
> >> +	u32 reg;
> >> +
> >> +	if (!(info->flags & GPIO_CONTROL))
> >> +		return -EINVAL;
> >> +
> >> +	pin_reg = &info->pin_regs[offset];
> >> +	if (pin_reg->mux_reg == -1)
> >> +		return -EINVAL;
> >> +
> >> +	reg = readl(ipctl->base + pin_reg->mux_reg);
> >> +	reg &= ~(0x7 << 20);
> >> +	writel(reg, ipctl->base + pin_reg->mux_reg);
> > 
> > Isn't this setup redundant at all, since imx_pmx_enable() already takes
> > care of setting mux register including GPIO mode?
> > 
> 
> Yes currently this is redundant, when a pinmux is actually applied. What
> is the expected behaviour? Is a explicit pinmux necessary before we can
> use GPIO? If not, maybe it would make more sense to use imx_pmx_enable
> here to write all pinctrl settings?

Okay, as per Documentation/pinctrl.txt, it's required that GPIO and
PINCTRL can be used as orthogonal.  That said, your code does the right
thing.  Sorry for the noisy comment.

> 
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int imx_pmx_gpio_set_direction(struct pinctrl_dev *pctldev,
> >> +	   struct pinctrl_gpio_range *range, unsigned offset, bool input)
> >> +{
> >> +	struct imx_pinctrl *ipctl = pinctrl_dev_get_drvdata(pctldev);
> >> +	const struct imx_pinctrl_soc_info *info = ipctl->info;
> >> +	const struct imx_pin_reg *pin_reg;
> >> +	u32 reg;
> >> +
> >> +	if (!(info->flags & GPIO_CONTROL))
> >> +		return -EINVAL;
> >> +
> >> +	pin_reg = &info->pin_regs[offset];
> >> +	if (pin_reg->mux_reg == -1)
> >> +		return -EINVAL;
> >> +
> >> +	reg = readl(ipctl->base + pin_reg->mux_reg);
> >> +	if (input)
> >> +		reg &= ~0x2;
> >> +	else
> >> +		reg |= 0x2;
> > 
> > This is all about Output Buffer Enable (OBE) bit.  What about Input
> > Buffer Enable (IBE) bit?  Don't we need to set or clear it as per GPIO
> > direction as well?
> > 
> 
> The leave the input buffer doesn't hurt, it allows to read back the
> value which is actually "on the wire". If a pin is hard on GND, one can
> actually see that.

Okay.

> 
> >> +	writel(reg, ipctl->base + pin_reg->mux_reg);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >>  static const struct pinmux_ops imx_pmx_ops = {
> >>  	.get_functions_count = imx_pmx_get_funcs_count,
> >>  	.get_function_name = imx_pmx_get_func_name,
> >>  	.get_function_groups = imx_pmx_get_groups,
> >> +	.gpio_request_enable = imx_pmx_gpio_request_enable,
> >> +	.gpio_set_direction = imx_pmx_gpio_set_direction,
> >>  	.enable = imx_pmx_enable,
> >>  };
> >>
> >> @@ -579,6 +628,11 @@ int imx_pinctrl_probe(struct platform_device *pdev,
> >>  		dev_err(&pdev->dev, "wrong pinctrl info\n");
> >>  		return -EINVAL;
> >>  	}
> >> +
> >> +	/* GPIO control functions only intended for shared mux/conf register */
> >> +	if (info->flags & GPIO_CONTROL)
> >> +		BUG_ON(!(info->flags & SHARE_MUX_CONF_REG));
> >> +
> > 
> > If this is always true, why don't we just use flag SHARE_MUX_CONF_REG
> > and save GPIO_CONTROL?  This check doesn't make too much sense to me if
> > we choose to have a new flag for GPIO setup.  IMO, we should probably
> > either drop the GPIO_CONTROL flag or the check.
> > 
> 
> Well, this is always true because the vf610 driver configures both
> configs. But when somebody accidentally enables GPIO_CONFIG without
> understanding the implications... This was more meant like "don't try to
> use the GPIO_CONTROL just like that, its Vybird specific".

But it will become a blocker if some day an i.MX controller (no flag
SHARE_MUX_CONF_REG) needs to use GPIO_CONFIG.

> But I'm ok to remove this runtime check, maybe a comment describing the
> flags is more appropriate..?

Sounds good.

Shawn