diff --git a/drivers/pinctrl/renesas/core.c b/drivers/pinctrl/renesas/core.c
index c528c124fb0e..9d168b90cd28 100644
--- a/drivers/pinctrl/renesas/core.c
+++ b/drivers/pinctrl/renesas/core.c
@@ -890,7 +890,7 @@ static void __init sh_pfc_check_drive_reg(const struct sh_pfc_soc_info *info,
 		if (!field->pin && !field->offset && !field->size)
 			continue;
 
-		mask = GENMASK(field->offset + field->size, field->offset);
+		mask = GENMASK(field->offset + field->size - 1, field->offset);
 		if (mask & seen)
 			sh_pfc_err("drive_reg 0x%x: field %u overlap\n",
 				   drive->reg, i);