arm: stellaris: make MII accesses complete immediately

When the guest attempts to start an MII register
access via the MCTL register, clear the START bit,
so that when the guest reads it back the register
transaction will be signalled as having completed.
This avoids the guest spinning as it polls the
START bit waiting for it to clear (which it
previously never would).

The  MII registers themselves still aren't implemented,
but at least we can avoid guests spending quite so much
time busy waiting.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1484938222-1423-1-git-send-email-peter.maydell@linaro.org
[PMM: expand commit message]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
index 957730e0237b9f7c155defa8e111235b73aab7f3..04bd10ada3f29c55342b488ea73ab43967f48145 100644 (file)
--- a/hw/net/stellaris_enet.c
+++ b/hw/net/stellaris_enet.c
@@ -416,7 +416,10 @@ static void stellaris_enet_write(void *opaque, hwaddr offset,
         s->thr = value;
         break;
     case 0x20: /* MCTL */
-        s->mctl = value;
+        /* TODO: MII registers aren't modelled.
+         * Clear START, indicating that the operation completes immediately.
+         */
+        s->mctl = value & ~1;
         break;
     case 0x24: /* MDV */
         s->mdv = value;