aspeed_sdmc: Init status always idle

The ast2500 SDRAM training routine busy waits on the 'init cycle busy
state' bit in DDR PHY Control/Status register #1 (MCR60).

This ensures the bit always reads zero, and allows training to
complete with upstream u-boot on the ast2500-evb.
Signed-off-by: NJoel Stanley <joel@jms.id.au>
Reviewed-by: NCédric Le Goater <clg@kaod.org>
Tested-by: NCédric Le Goater <clg@kaod.org>
Message-id: 20180807075757.7242-5-joel@jms.id.au
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/misc/aspeed_sdmc.c

@@ -23,6 +23,10 @@
 /* Configuration Register */
 #define R_CONF            (0x04 / 4)
 
+/* Control/Status Register #1 (ast2500) */
+#define R_STATUS1         (0x60 / 4)
+#define   PHY_BUSY_STATE      BIT(0)
+
 /*
  * Configuration register Ox4 (for Aspeed AST2400 SOC)
  *
@@ -137,6 +141,17 @@ static void aspeed_sdmc_write(void *opaque, hwaddr addr, uint64_t data,
             g_assert_not_reached();
         }
     }
+    if (s->silicon_rev == AST2500_A0_SILICON_REV ||
+            s->silicon_rev == AST2500_A1_SILICON_REV) {
+        switch (addr) {
+        case R_STATUS1:
+            /* Will never return 'busy' */
+            data &= ~PHY_BUSY_STATE;
+            break;
+        default:
+            break;
+        }
+    }
 
     s->regs[addr] = data;
 }