hw/net/imx_fec: Support two Ethernet interfaces connected to single MDIO bus

The SOC on i.MX6UL and i.MX7 has 2 Ethernet interfaces. The PHY on each may
be connected to separate MDIO busses, or both may be connected on the same
MDIO bus using different PHY addresses. Commit 461c51ad42 ("Add a phy-num
property to the i.MX FEC emulator") added support for specifying PHY
addresses, but it did not provide support for linking the second PHY on
a given MDIO bus to the other Ethernet interface.

To be able to support two PHY instances on a single MDIO bus, two properties
are needed: First, there needs to be a flag indicating if the MDIO bus on
a given Ethernet interface is connected. If not, attempts to read from this
bus must always return 0xffff. Implement this property as phy-connected.
Second, if the MDIO bus on an interface is active, it needs a link to the
consumer interface to be able to provide PHY access for it. Implement this
property as phy-consumer.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20230315145248.1639364-2-linux@roeck-us.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/net/imx_fec.c

@@ -282,11 +282,19 @@ static uint32_t imx_phy_read(IMXFECState *s, int reg)
     uint32_t val;
     uint32_t phy = reg / 32;
 
-    if (phy != s->phy_num) {
-        trace_imx_phy_read_num(phy, s->phy_num);
+    if (!s->phy_connected) {
         return 0xffff;
     }
 
+    if (phy != s->phy_num) {
+        if (s->phy_consumer && phy == s->phy_consumer->phy_num) {
+            s = s->phy_consumer;
+        } else {
+            trace_imx_phy_read_num(phy, s->phy_num);
+            return 0xffff;
+        }
+    }
+
     reg %= 32;
 
     switch (reg) {
@@ -343,11 +351,19 @@ static void imx_phy_write(IMXFECState *s, int reg, uint32_t val)
 {
     uint32_t phy = reg / 32;
 
-    if (phy != s->phy_num) {
-        trace_imx_phy_write_num(phy, s->phy_num);
+    if (!s->phy_connected) {
         return;
     }
 
+    if (phy != s->phy_num) {
+        if (s->phy_consumer && phy == s->phy_consumer->phy_num) {
+            s = s->phy_consumer;
+        } else {
+            trace_imx_phy_write_num(phy, s->phy_num);
+            return;
+        }
+    }
+
     reg %= 32;
 
     trace_imx_phy_write(val, phy, reg);
@@ -1327,6 +1343,9 @@ static Property imx_eth_properties[] = {
     DEFINE_NIC_PROPERTIES(IMXFECState, conf),
     DEFINE_PROP_UINT32("tx-ring-num", IMXFECState, tx_ring_num, 1),
     DEFINE_PROP_UINT32("phy-num", IMXFECState, phy_num, 0),
+    DEFINE_PROP_BOOL("phy-connected", IMXFECState, phy_connected, true),
+    DEFINE_PROP_LINK("phy-consumer", IMXFECState, phy_consumer, TYPE_IMX_FEC,
+                     IMXFECState *),
     DEFINE_PROP_END_OF_LIST(),
 };
 

include/hw/net/imx_fec.h

@@ -270,6 +270,8 @@ struct IMXFECState {
     uint32_t phy_int;
     uint32_t phy_int_mask;
     uint32_t phy_num;
+    bool phy_connected;
+    struct IMXFECState *phy_consumer;
 
     bool is_fec;