pinctrl: freescale: imx: allow mux_reg offset zero

Allow mux_reg offset zero to be a valid pin_id, on imx7d
mux_conf reg offset is zero for iomuxc-lspr controller

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-imx.c

@@ -542,6 +542,9 @@ static int imx_pinctrl_parse_groups(struct device_node *np,
 		struct imx_pin_reg *pin_reg;
 		struct imx_pin *pin = &grp->pins[i];
 
+		if (!(info->flags & ZERO_OFFSET_VALID) && !mux_reg)
+			mux_reg = -1;
+
 		if (info->flags & SHARE_MUX_CONF_REG) {
 			conf_reg = mux_reg;
 		} else {
@@ -550,7 +553,7 @@ static int imx_pinctrl_parse_groups(struct device_node *np,
 				conf_reg = -1;
 		}
 
-		pin_id = mux_reg ? mux_reg / 4 : conf_reg / 4;
+		pin_id = (mux_reg != -1) ? mux_reg / 4 : conf_reg / 4;
 		pin_reg = &info->pin_regs[pin_id];
 		pin->pin = pin_id;
 		grp->pin_ids[i] = pin_id;

drivers/pinctrl/freescale/pinctrl-imx.h

@@ -85,6 +85,7 @@ struct imx_pinctrl_soc_info {
 };
 
 #define SHARE_MUX_CONF_REG	0x1
+#define ZERO_OFFSET_VALID	0x2
 
 #define NO_MUX		0x0
 #define NO_PAD		0x0