ARM: tegra: cpufreq: Adjust memory frequency with cpu frequency

Adjusts the minimum memory frequency when the cpu frequency
changes.  The values are currently hardcoded to a reasonable
default.  If memory frequency scaling is not enabled this
patch will have no effect.
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Colin Cross <ccross@android.com>

arch/arm/mach-tegra/cpu-tegra.c

@@ -51,6 +51,7 @@ static struct cpufreq_frequency_table freq_table[] = {
 #define NUM_CPUS	2
 
 static struct clk *cpu_clk;
+static struct clk *emc_clk;
 
 static unsigned long target_cpu_speed[NUM_CPUS];
 static DEFINE_MUTEX(tegra_cpu_lock);
@@ -83,6 +84,17 @@ static int tegra_update_cpu_speed(unsigned long rate)
 	if (freqs.old == freqs.new)
 		return ret;
 
+	/*
+	 * Vote on memory bus frequency based on cpu frequency
+	 * This sets the minimum frequency, display or avp may request higher
+	 */
+	if (rate >= 816000)
+		clk_set_rate(emc_clk, 600000000); /* cpu 816 MHz, emc max */
+	else if (rate >= 456000)
+		clk_set_rate(emc_clk, 300000000); /* cpu 456 MHz, emc 150Mhz */
+	else
+		clk_set_rate(emc_clk, 100000000);  /* emc 50Mhz */
+
 	for_each_online_cpu(freqs.cpu)
 		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
 
@@ -173,6 +185,13 @@ static int tegra_cpu_init(struct cpufreq_policy *policy)
 	if (IS_ERR(cpu_clk))
 		return PTR_ERR(cpu_clk);
 
+	emc_clk = clk_get_sys("cpu", "emc");
+	if (IS_ERR(emc_clk)) {
+		clk_put(cpu_clk);
+		return PTR_ERR(emc_clk);
+	}
+
+	clk_enable(emc_clk);
 	clk_enable(cpu_clk);
 
 	cpufreq_frequency_table_cpuinfo(policy, freq_table);
@@ -195,6 +214,8 @@ static int tegra_cpu_init(struct cpufreq_policy *policy)
 static int tegra_cpu_exit(struct cpufreq_policy *policy)
 {
 	cpufreq_frequency_table_cpuinfo(policy, freq_table);
+	clk_disable(emc_clk);
+	clk_put(emc_clk);
 	clk_put(cpu_clk);
 	return 0;
 }