[PATCH] gpio/generic: initialize the shadow of direction register

[Lothar Waßmann]

Hi,

Shawn Guo writes:
> On Tue, May 15, 2012 at 09:17:50AM +0200, Lothar Waßmann wrote:
> > This will blow up in your face when calling bgpio_init() without any
> > direction register (which is well supported by the generic driver).
> > 
> > You need to do this in the platform specific driver that uses the
> > generic driver. See gpio-mxc.c for reference:
> > |        err = bgpio_init(&port->bgc, &pdev->dev, 4,
> > |                         port->base + GPIO_PSR,
> > |                         port->base + GPIO_DR, NULL,
> > |                         port->base + GPIO_GDIR, NULL, false);
> > |        if (err)
> > |                goto out_iounmap;
> > |
> > |        port->bgc.gc.to_irq = mxc_gpio_to_irq;
> > |        port->bgc.gc.base = pdev->id * 32;
> > |        port->bgc.dir = port->bgc.read_reg(port->bgc.reg_dir);
> > |        port->bgc.data = port->bgc.read_reg(port->bgc.reg_set);
> > 
> Ah, thanks for the info.  I did not know that we ran into the issue
> on gpio-mxc and had it fixed there.  But instead of asking every
> single platform gpio driver to do the fixup, we should really fix it
> in generic driver.  Imaging if you fixed the issue in gpio-generic
> when you ran into the problem on MXC/IMX, I wouldn't have spent half
> day to track the issue down on MXS :)
> 
> So back to the right fixing, does the following one look good to you?
> 
> @@ -394,6 +394,10 @@ int bgpio_init(struct bgpio_chip *bgc, struct device *dev,
>                 return ret;
> 
>         bgc->data = bgc->read_reg(bgc->reg_dat);
> +       if (bgc->gc.set == bgpio_set_set)
> +               bgc->data = bgc->read_reg(bgc->reg_set);
> +       if (bgc->reg_dir)
> +               bgc->dir = bgc->read_reg(bgc->reg_dir);
> 
>         return ret;
>  }
> 
That might change the behaviour of existing implementations.


Lothar Waßmann
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