On Fri, 2013-11-22 at 14:51 -0600, Kumar Gala wrote:

quoted

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