netdev - [PATCH net 2/2] net: mscc: ocelot: warn when encoding an out-of-bounds watermark value

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Date:   Mon,  5 Oct 2020 12:09:12 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     davem@...emloft.net
Cc:     alexandre.belloni@...tlin.com, andrew@...n.ch,
        f.fainelli@...il.com, vivien.didelot@...il.com,
        alexandru.marginean@....com, claudiu.manoil@....com,
        xiaoliang.yang_1@....com, hongbo.wang@....com,
        netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com
Subject: [PATCH net 2/2] net: mscc: ocelot: warn when encoding an out-of-bounds watermark value

There is an upper bound to the value that a watermark may hold. That
upper bound is not immediately obvious during configuration, and it
might be possible to have accidental truncation.

Actually this has happened already, add a warning to prevent it from
happening again.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/dsa/ocelot/felix_vsc9959.c     | 2 ++
 drivers/net/dsa/ocelot/seville_vsc9953.c   | 2 ++
 drivers/net/ethernet/mscc/ocelot_vsc7514.c | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index 4fc67ff212de..cb0f3d28ecac 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -998,6 +998,8 @@ static int vsc9959_prevalidate_phy_mode(struct ocelot *ocelot, int port,
  */
 static u16 vsc9959_wm_enc(u16 value)
 {
+	WARN_ON(value >= 16 * BIT(8));
+
 	if (value >= BIT(8))
 		return BIT(8) | (value / 16);
 
diff --git a/drivers/net/dsa/ocelot/seville_vsc9953.c b/drivers/net/dsa/ocelot/seville_vsc9953.c
index e993f3eac3eb..76576cf0ba8a 100644
--- a/drivers/net/dsa/ocelot/seville_vsc9953.c
+++ b/drivers/net/dsa/ocelot/seville_vsc9953.c
@@ -1049,6 +1049,8 @@ static int vsc9953_prevalidate_phy_mode(struct ocelot *ocelot, int port,
  */
 static u16 vsc9953_wm_enc(u16 value)
 {
+	WARN_ON(value >= 16 * BIT(9));
+
 	if (value >= BIT(9))
 		return BIT(9) | (value / 16);
 
diff --git a/drivers/net/ethernet/mscc/ocelot_vsc7514.c b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
index f3e54589e6d6..79b88bc69c75 100644
--- a/drivers/net/ethernet/mscc/ocelot_vsc7514.c
+++ b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
@@ -754,6 +754,8 @@ static int ocelot_reset(struct ocelot *ocelot)
  */
 static u16 ocelot_wm_enc(u16 value)
 {
+	WARN_ON(value >= 16 * BIT(8));
+
 	if (value >= BIT(8))
 		return BIT(8) | (value / 16);
 
-- 
2.25.1