[PATCH 09/10] pinctrl: mediatek: Prevent divide-by-zero for pins with fixed drive strength

[Lee Jones]

mtk_drive[] only defines entries for DRV_GRP0 (1) through DRV_GRP4 (5),
leaving mtk_drive[DRV_FIXED] (0) zero-initialised with min = 0, max = 0,
step = 0, and scal = 0.  If mtk_pinconf_drive_set() or
mtk_pinconf_drive_set_rev1() is called with arg = 0 on a pin with
drv_n == DRV_FIXED, the range check (0 >= 0 && 0 <= 0) succeeds and
!(arg % tb->step) divides by zero.  Similarly, mtk_pinconf_drive_get()
and mtk_pinconf_drive_get_rev1() divide by tb->scal (0) if the pin has
drive register fields defined.

Return -ENOTSUPP immediately when desc->drv_n == DRV_FIXED.

Fixes: c28321979ba8 ("pinctrl: mediatek: add driving strength related support to pinctrl-mtk-common-v2.c")
Closes: https://sashiko.dev/#/bug/linux-d3852d37-6806-4c41-a493-f249dd59d0c6
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
---
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c b/drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c
index aa15c9e047d8..1243862983b9 100644
--- a/drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c
+++ b/drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c
@@ -1040,6 +1040,9 @@ int mtk_pinconf_drive_set(struct mtk_pinctrl *hw,
 	const struct mtk_drive_desc *tb;
 	int err = -ENOTSUPP;
 
+	if (desc->drv_n == DRV_FIXED)
+		return -ENOTSUPP;
+
 	tb = &mtk_drive[desc->drv_n];
 	/* 4mA when (e8, e4) = (0, 0)
 	 * 8mA when (e8, e4) = (0, 1)
@@ -1069,6 +1072,9 @@ int mtk_pinconf_drive_get(struct mtk_pinctrl *hw,
 	const struct mtk_drive_desc *tb;
 	int err, val1, val2;
 
+	if (desc->drv_n == DRV_FIXED)
+		return -ENOTSUPP;
+
 	tb = &mtk_drive[desc->drv_n];
 
 	err = mtk_hw_get_value(hw, desc, PINCTRL_PIN_REG_E4, &val1);
@@ -1095,6 +1101,9 @@ int mtk_pinconf_drive_set_rev1(struct mtk_pinctrl *hw,
 	const struct mtk_drive_desc *tb;
 	int err = -ENOTSUPP;
 
+	if (desc->drv_n == DRV_FIXED)
+		return -ENOTSUPP;
+
 	tb = &mtk_drive[desc->drv_n];
 
 	if ((arg >= tb->min && arg <= tb->max) && !(arg % tb->step)) {
@@ -1116,6 +1125,9 @@ int mtk_pinconf_drive_get_rev1(struct mtk_pinctrl *hw,
 	const struct mtk_drive_desc *tb;
 	int err, val1;
 
+	if (desc->drv_n == DRV_FIXED)
+		return -ENOTSUPP;
+
 	tb = &mtk_drive[desc->drv_n];
 
 	err = mtk_hw_get_value(hw, desc, PINCTRL_PIN_REG_DRV, &val1);
-- 
2.56.0.385.gac671c819a-goog