[PATCH] net/cadence_gem: Set PHY autonegotiation restart status

[linus.ziegert@holoplot.com]

From: Linus Ziegert <linus.ziegert+qemu@holoplot.com>

The Linux kernel PHY driver sets AN_RESTART in the BMCR of the
PHY when autonegotiation is started.
Recently the kernel started to read back the PHY's AN_RESTART
bit and now checks whether the autonegotiation is complete and
the bit was cleared [1]. Otherwise the link status is down.

The emulated PHY needs to clear AN_RESTART immediately to inform
the kernel driver about the completion of autonegotiation phase.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c36757eb9dee

Signed-off-by: Linus Ziegert <linus.ziegert+qemu@holoplot.com>
---
 hw/net/cadence_gem.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
index 7f9cb5ab95..b8be73dc55 100644
--- a/hw/net/cadence_gem.c
+++ b/hw/net/cadence_gem.c
@@ -271,9 +271,10 @@
 #define PHY_REG_EXT_PHYSPCFC_ST   27
 #define PHY_REG_CABLE_DIAG   28
 
-#define PHY_REG_CONTROL_RST  0x8000
-#define PHY_REG_CONTROL_LOOP 0x4000
-#define PHY_REG_CONTROL_ANEG 0x1000
+#define PHY_REG_CONTROL_RST       0x8000
+#define PHY_REG_CONTROL_LOOP      0x4000
+#define PHY_REG_CONTROL_ANEG      0x1000
+#define PHY_REG_CONTROL_ANRESTART 0x0200
 
 #define PHY_REG_STATUS_LINK     0x0004
 #define PHY_REG_STATUS_ANEGCMPL 0x0020
@@ -1345,7 +1346,7 @@ static void gem_phy_write(CadenceGEMState *s, unsigned reg_num, uint16_t val)
         }
         if (val & PHY_REG_CONTROL_ANEG) {
             /* Complete autonegotiation immediately */
-            val &= ~PHY_REG_CONTROL_ANEG;
+            val &= ~(PHY_REG_CONTROL_ANEG | PHY_REG_CONTROL_ANRESTART);
             s->phy_regs[PHY_REG_STATUS] |= PHY_REG_STATUS_ANEGCMPL;
         }
         if (val & PHY_REG_CONTROL_LOOP) {
-- 
2.21.0