arm: mxs: Wait for DRAM to start

Instead of waiting for a fixed period of time and hoping for the best
that the DRAM will start, read back an EMI status register which tells
us exactly when the DRAM started.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>

arch/arm/cpu/arm926ejs/mxs/spl_mem_init.c

@@ -274,7 +274,13 @@ static void mx23_mem_init(void)
 	setbits_le32(MXS_DRAM_BASE + 0x20, 1 << 16);
 
 	clrbits_le32(MXS_DRAM_BASE + 0x40, 1 << 17);
-	early_delay(20000);
+
+	/* Wait for EMI_STAT bit DRAM_HALTED */
+	for (;;) {
+		if (!(readl(MXS_EMI_BASE + 0x10) & (1 << 1)))
+			break;
+		early_delay(1000);
+	}
 
 	/* Adjust EMI port priority. */
 	clrsetbits_le32(0x80020000, 0x1f << 16, 0x2);