pinctrl: re-enable old state in case of error in pinctrl_select_state

If a new state is applied, the groups configured in the old state but
not in the new state are disabled.
If something goes wrong and the new state can't be applied, we have to
re-enable those groups.
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.c

@@ -897,6 +897,7 @@ static int pinctrl_select_state_locked(struct pinctrl *p,
 				       struct pinctrl_state *state)
 {
 	struct pinctrl_setting *setting, *setting2;
+	struct pinctrl_state *old_state = p->state;
 	int ret;
 
 	if (p->state == state)
@@ -973,7 +974,24 @@ static int pinctrl_select_state_locked(struct pinctrl *p,
 		pinctrl_free_setting(true, setting2);
 	}
 reapply_old_state:
-	/* FIXME: re-enable old setting */
+	if (old_state) {
+		list_for_each_entry(setting, &old_state->settings, node) {
+			bool found = false;
+			if (setting->type != PIN_MAP_TYPE_MUX_GROUP)
+				continue;
+			list_for_each_entry(setting2, &state->settings, node) {
+				if (setting2->type != PIN_MAP_TYPE_MUX_GROUP)
+					continue;
+				if (setting2->data.mux.group ==
+						setting->data.mux.group) {
+					found = true;
+					break;
+				}
+			}
+			if (!found)
+				pinmux_enable_setting(setting);
+		}
+	}
 	return ret;
 }