e1000: improve auto-negotiation reporting via mii-tool

Using mii-tool (on F20-live), the following output is produced:

  SIOCGMIIREG on ens3 failed: Input/output error
  ens3: no autonegotiation, 1000baseT-FD flow-control, link ok

The first line (SIOCGMIIREG error) is due to mii-tool's inability
to read the PHY auto-negotiation expansion register.
On the second line, "no autonegotiation" is wrong, and caused by
the absence of a flag in the link partner ability register which
would indicate that our link partner has acked us. This flag is
listed as "reserved" in the Intel e1000 manual, but mii-tool uses
it as LPA_LPACK from /usr/include/linux/mii.h.

This patch adds read access to PHY_AUTONEG_EXP and defines the
link partner ack flag, allowing mii-tool to generate output as
normally expected:

  ens3: negotiated 1000baseT-FD flow-control, link ok

Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/net/e1000.c

@@ -176,6 +176,7 @@ e1000_link_down(E1000State *s)
     s->mac_reg[STATUS] &= ~E1000_STATUS_LU;
     s->phy_reg[PHY_STATUS] &= ~MII_SR_LINK_STATUS;
     s->phy_reg[PHY_STATUS] &= ~MII_SR_AUTONEG_COMPLETE;
+    s->phy_reg[PHY_LP_ABILITY] &= ~MII_LPAR_LPACK;
 }
 
 static void
@@ -209,6 +210,7 @@ e1000_autoneg_timer(void *opaque)
     E1000State *s = opaque;
     if (!qemu_get_queue(s->nic)->link_down) {
         e1000_link_up(s);
+        s->phy_reg[PHY_LP_ABILITY] |= MII_LPAR_LPACK;
         s->phy_reg[PHY_STATUS] |= MII_SR_AUTONEG_COMPLETE;
         DBGOUT(PHY, "Auto negotiation is completed\n");
     }
@@ -227,7 +229,8 @@ static const char phy_regcap[0x20] = {
     [PHY_CTRL] = PHY_RW,	[PHY_1000T_CTRL] = PHY_RW,
     [PHY_LP_ABILITY] = PHY_R,	[PHY_1000T_STATUS] = PHY_R,
     [PHY_AUTONEG_ADV] = PHY_RW,	[M88E1000_RX_ERR_CNTR] = PHY_R,
-    [PHY_ID2] = PHY_R,		[M88E1000_PHY_SPEC_STATUS] = PHY_R
+    [PHY_ID2] = PHY_R,		[M88E1000_PHY_SPEC_STATUS] = PHY_R,
+    [PHY_AUTONEG_EXP] = PHY_R,
 };
 
 /* PHY_ID2 documented in 8254x_GBe_SDM.pdf, pp. 250 */

hw/net/e1000_regs.h

@@ -384,6 +384,9 @@
 #define MII_SR_100X_FD_CAPS      0x4000	/* 100X  Full Duplex Capable */
 #define MII_SR_100T4_CAPS        0x8000	/* 100T4 Capable */
 
+/* PHY Link Partner Ability Register */
+#define MII_LPAR_LPACK           0x4000 /* Acked by link partner */
+
 /* Interrupt Cause Read */
 #define E1000_ICR_TXDW          0x00000001 /* Transmit desc written back */
 #define E1000_ICR_TXQE          0x00000002 /* Transmit Queue empty */