pinctrl: mediatek: paris: Fix PIN_CONFIG_BIAS_* readback

When reading back pin bias settings, if the pin is not in the
corresponding bias state, the function should return -EINVAL.

Fix this in the mediatek-paris pinctrl library so that the read back
state is not littered with bogus a "input bias disabled" combined with
"pull up" or "pull down" states.

Fixes: 80525098 ("pinctrl: mediatek: add pinctrl-paris that implements the vendor dt-bindings")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220308100956.2750295-3-wenst@chromium.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-paris.c

@@ -96,20 +96,16 @@ static int mtk_pinconf_get(struct pinctrl_dev *pctldev,
 			err = hw->soc->bias_get_combo(hw, desc, &pullup, &ret);
 			if (err)
 				goto out;
+			if (ret == MTK_PUPD_SET_R1R0_00)
+				ret = MTK_DISABLE;
 			if (param == PIN_CONFIG_BIAS_DISABLE) {
-				if (ret == MTK_PUPD_SET_R1R0_00)
-					ret = MTK_DISABLE;
+				if (ret != MTK_DISABLE)
+					err = -EINVAL;
 			} else if (param == PIN_CONFIG_BIAS_PULL_UP) {
-				/* When desire to get pull-up value, return
-				 *  error if current setting is pull-down
-				 */
-				if (!pullup)
+				if (!pullup || ret == MTK_DISABLE)
 					err = -EINVAL;
 			} else if (param == PIN_CONFIG_BIAS_PULL_DOWN) {
-				/* When desire to get pull-down value, return
-				 *  error if current setting is pull-up
-				 */
-				if (pullup)
+				if (pullup || ret == MTK_DISABLE)
 					err = -EINVAL;
 			}
 		} else {