On Fri, 2013-11-22 at 14:51 -0600, Kumar Gala wrote: > > drivers/gpio/gpio-mpc8xxx.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpio/gpio-mpc8xxx.c b/drivers/gpio/gpio-mpc8xxx.c > > index 914e859..d7d6d72 100644 > > --- a/drivers/gpio/gpio-mpc8xxx.c > > +++ b/drivers/gpio/gpio-mpc8xxx.c > > @@ -70,10 +70,14 @@ static int mpc8572_gpio_get(struct gpio_chip *gc, > > unsigned int gpio) > > u32 val; > > struct of_mm_gpio_chip *mm = to_of_mm_gpio_chip(gc); > > struct mpc8xxx_gpio_chip *mpc8xxx_gc = to_mpc8xxx_gpio_chip(mm); > > + u32 out_mask, out_shadow; > > > > - val = in_be32(mm->regs + GPIO_DAT) & ~in_be32(mm->regs + GPIO_DIR); > > + out_mask = in_be32(mm->regs + GPIO_DIR); > > > > - return (val | mpc8xxx_gc->data) & mpc8xxx_gpio2mask(gpio); > > + val = in_be32(mm->regs + GPIO_DAT) & ~out_mask; > > + out_shadow = mpc8xxx_gc->data & out_mask; > > + > > + return (val | out_shadow) & mpc8xxx_gpio2mask(gpio); > > } > > I really think a comment is worth adding here about why we do this. > > - k
Hi, Kumar, Thanks for your comment. In fact, there already had some comments above the function: /* Workaround GPIO 1 errata on MPC8572/MPC8536. The status of GPIOs * defined as output cannot be determined by reading GPDAT register, * so we use shadow data register instead. The status of input pins * is determined by reading GPDAT register. */ Best Regards, Liu Gang _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
