[PATCH net] net: sparx5: fix source port register when mirroring

[Daniel Machon]

When port mirroring is added to a port, the bit position of the source
port, needs to be written to the register ANA_AC_PROBE_PORT_CFG.  This
register is replicated for n_ports > 32, and therefore we need to derive
the correct register from the port number.

Before this patch, we wrongly calculate the register from portno /
BITS_PER_BYTE, where the divisor ought to be 32, causing any port >=8 to
be written to the wrong register. We fix this, by using do_div(), where
the dividend is the register, the remainder is the bit position and the
divisor is now 32.

Fixes: 4e50d72b3b95 ("net: sparx5: add port mirroring implementation")
Signed-off-by: Daniel Machon <daniel.machon at microchip.com>
---
 drivers/net/ethernet/microchip/sparx5/sparx5_mirror.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_mirror.c b/drivers/net/ethernet/microchip/sparx5/sparx5_mirror.c
index 15db423be4aa..459a53676ae9 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_mirror.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_mirror.c
@@ -31,10 +31,10 @@ static u64 sparx5_mirror_port_get(struct sparx5 *sparx5, u32 idx)
 /* Add port to mirror (only front ports) */
 static void sparx5_mirror_port_add(struct sparx5 *sparx5, u32 idx, u32 portno)
 {
-	u32 val, reg = portno;
+	u64 reg = portno;
+	u32 val;
 
-	reg = portno / BITS_PER_BYTE;
-	val = BIT(portno % BITS_PER_BYTE);
+	val = BIT(do_div(reg, 32));
 
 	if (reg == 0)
 		return spx5_rmw(val, val, sparx5, ANA_AC_PROBE_PORT_CFG(idx));
@@ -45,10 +45,10 @@ static void sparx5_mirror_port_add(struct sparx5 *sparx5, u32 idx, u32 portno)
 /* Delete port from mirror (only front ports) */
 static void sparx5_mirror_port_del(struct sparx5 *sparx5, u32 idx, u32 portno)
 {
-	u32 val, reg = portno;
+	u64 reg = portno;
+	u32 val;
 
-	reg = portno / BITS_PER_BYTE;
-	val = BIT(portno % BITS_PER_BYTE);
+	val = BIT(do_div(reg, 32));
 
 	if (reg == 0)
 		return spx5_rmw(0, val, sparx5, ANA_AC_PROBE_PORT_CFG(idx));

---
base-commit: 36efaca9cb28a893cad98f0448c39a8b698859e2
change-id: 20241009-mirroring-fix-a593bdcba644

Best regards,
-- 
Daniel Machon <daniel.machon at microchip.com>