On Fri, 22 Nov 2013 16:12:40 +0800 Liu Gang <gang....@freescale.com> wrote:
> For MPC8572/MPC8536, the status of GPIOs defined as output > cannot be determined by reading GPDAT register, so the code > use shadow data register instead. But the code may give the > wrong status of GPIOs defined as input under some scenarios: > > 1. If some pins were configured as inputs and were asserted > high before booting the kernel, the shadow data has been > initialized with those pin values. > 2. Some pins have been configured as output first and have > been set to the high value, then reconfigured as input. > > The above cases will make the shadow data for those input > pins to be set to high. Then reading the pin status will > always return high even if the actual pin status is low. > > The code should eliminate the effects of the shadow data to > the input pins, and the status of those pins should be > read directly from GPDAT. > > Signed-off-by: Liu Gang <gang....@freescale.com> > --- > changes in v2: > - Added more description of the problem. > - Reduced one in_be32() call. > - Do not modify the shadow data. > > 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); > } > > static int mpc8xxx_gpio_get(struct gpio_chip *gc, unsigned int gpio) Acked-by: Anatolij Gustschin <ag...@denx.de> _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
