cpufreq: qoriq: enhance bus frequency calculation

On some platforms, property device-type may be missed in soc node
in dts which caused the bus-frequency can not be obtained correctly.

This patch enhanced the bus-frequency calculation. When property
device-type is missed in dts, bus-frequency will be obtained by
looking up clock table to get platform clock and hence get its
frequency.
Signed-off-by: Tang Yuantian <andy.tang@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/qoriq-cpufreq.c

@@ -52,17 +52,27 @@ static u32 get_bus_freq(void)
 {
 	struct device_node *soc;
 	u32 sysfreq;
+	struct clk *pltclk;
+	int ret;
 
+	/* get platform freq by searching bus-frequency property */
 	soc = of_find_node_by_type(NULL, "soc");
-	if (!soc)
-		return 0;
-
-	if (of_property_read_u32(soc, "bus-frequency", &sysfreq))
-		sysfreq = 0;
+	if (soc) {
+		ret = of_property_read_u32(soc, "bus-frequency", &sysfreq);
+		of_node_put(soc);
+		if (!ret)
+			return sysfreq;
+	}
 
-	of_node_put(soc);
+	/* get platform freq by its clock name */
+	pltclk = clk_get(NULL, "cg-pll0-div1");
+	if (IS_ERR(pltclk)) {
+		pr_err("%s: can't get bus frequency %ld\n",
+		       __func__, PTR_ERR(pltclk));
+		return PTR_ERR(pltclk);
+	}
 
-	return sysfreq;
+	return clk_get_rate(pltclk);
 }
 
 static struct clk *cpu_to_clk(int cpu)