memory: tegra: Add EMC (external memory controller) driver

Implements functionality needed to change the rate of the memory bus
clock.
Signed-off-by: NMikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/memory/tegra/Kconfig

@@ -5,3 +5,13 @@ config TEGRA_MC
 	help
 	  This driver supports the Memory Controller (MC) hardware found on
 	  NVIDIA Tegra SoCs.
+
+config TEGRA124_EMC
+	bool "NVIDIA Tegra124 External Memory Controller driver"
+	default y
+	depends on TEGRA_MC && ARCH_TEGRA_124_SOC
+	help
+	  This driver is for the External Memory Controller (EMC) found on
+	  Tegra124 chips. The EMC controls the external DRAM on the board.
+	  This driver is required to change memory timings / clock rate for
+	  external memory.

drivers/memory/tegra/Makefile

@@ -5,3 +5,5 @@ tegra-mc-$(CONFIG_ARCH_TEGRA_114_SOC) += tegra114.o
 tegra-mc-$(CONFIG_ARCH_TEGRA_124_SOC) += tegra124.o
 
 obj-$(CONFIG_TEGRA_MC) += tegra-mc.o
+
+obj-$(CONFIG_TEGRA124_EMC) += tegra124-emc.o

include/soc/tegra/emc.h

+/*
+ * Copyright (c) 2014 NVIDIA Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __SOC_TEGRA_EMC_H__
+#define __SOC_TEGRA_EMC_H__
+
+struct tegra_emc;
+
+int tegra_emc_prepare_timing_change(struct tegra_emc *emc,
+				    unsigned long rate);
+void tegra_emc_complete_timing_change(struct tegra_emc *emc,
+				      unsigned long rate);
+
+#endif /* __SOC_TEGRA_EMC_H__ */