gpio: gpio-generic: add flag to read out output value from reg_set

The change introduces BGPIOF_READ_OUTPUT_REG_SET flag for gpio-generic
GPIO chip implementation, which allows to get correct configured value
from reg_set register, input value is still get from reg_dat.

Signed-off-by: Vladimir Zapolskiy <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-generic.c

···
 	return 1 << (bgc->bits - 1 - pin);
 }
 
+static int bgpio_get_set(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct bgpio_chip *bgc = to_bgpio_chip(gc);
+	unsigned long pinmask = bgc->pin2mask(bgc, gpio);
+
+	if (bgc->dir & pinmask)
+		return bgc->read_reg(bgc->reg_set) & pinmask;
+	else
+		return bgc->read_reg(bgc->reg_dat) & pinmask;
+}
+
 static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
 {
 	struct bgpio_chip *bgc = to_bgpio_chip(gc);
···
 static int bgpio_setup_io(struct bgpio_chip *bgc,
 			  void __iomem *dat,
 			  void __iomem *set,
-			  void __iomem *clr)
+			  void __iomem *clr,
+			  unsigned long flags)
 {
 
 	bgc->reg_dat = dat;
···
 		bgc->gc.set_multiple = bgpio_set_multiple;
 	}
 
-	bgc->gc.get = bgpio_get;
+	if (!(flags & BGPIOF_UNREADABLE_REG_SET) &&
+	    (flags & BGPIOF_READ_OUTPUT_REG_SET))
+		bgc->gc.get = bgpio_get_set;
+	else
+		bgc->gc.get = bgpio_get;
 
 	return 0;
 }
···
 	bgc->gc.ngpio = bgc->bits;
 	bgc->gc.request = bgpio_request;
 
-	ret = bgpio_setup_io(bgc, dat, set, clr);
+	ret = bgpio_setup_io(bgc, dat, set, clr, flags);
 	if (ret)
 		return ret;
 

include/linux/basic_mmio_gpio.h

···
 #define BGPIOF_UNREADABLE_REG_SET	BIT(1) /* reg_set is unreadable */
 #define BGPIOF_UNREADABLE_REG_DIR	BIT(2) /* reg_dir is unreadable */
 #define BGPIOF_BIG_ENDIAN_BYTE_ORDER	BIT(3)
+#define BGPIOF_READ_OUTPUT_REG_SET     BIT(4) /* reg_set stores output value */
 
 #endif /* __BASIC_MMIO_GPIO_H */