pinctrl: mediatek: add EINT support to virtual GPIOs

Virtual gpio only used inside SOC and not being exported to outside SOC.
Some modules use virtual gpio as eint and doesn't need SMT.
So this patch add EINT support to virtual GPIOs.
Signed-off-by: Chuanjia Liu <Chuanjia.Liu@mediatek.com>
Acked-by: Sean Wang <sean.wang@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c

@@ -290,7 +290,13 @@ static int mtk_xt_set_gpio_as_eint(void *data, unsigned long eint_n)
 		return err;
 
 	err = mtk_hw_set_value(hw, desc, PINCTRL_PIN_REG_SMT, MTK_ENABLE);
-	if (err)
+	/* SMT is supposed to be supported by every real GPIO and doesn't
+	 * support virtual GPIOs, so the extra condition err != -ENOTSUPP
+	 * is just for adding EINT support to these virtual GPIOs. It should
+	 * add an extra flag in the pin descriptor when more pins with
+	 * distinctive characteristic come out.
+	 */
+	if (err && err != -ENOTSUPP)
 		return err;
 
 	return 0;