memory: tegra124-emc: Make driver modular

Add modularization support to the Tegra124 EMC driver, which now can be
compiled as a loadable kernel module.

Note that EMC clock must be registered at clk-init time, otherwise PLLM
will be disabled as unused clock at boot time if EMC driver is compiled
as a module. Hence add a prepare/complete callbacks. similarly to what is
done for the Tegra20/30 EMC drivers.

Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20201228154920.18846-2-digetx@gmail.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

2 files changed, 23 insertions, 11 deletions

diff --git a/drivers/memory/tegra/Kconfig b/drivers/memory/tegra/Kconfig
index ca7077a06f4c..f5b451403c58 100644
--- a/drivers/memory/tegra/Kconfig
+++ b/drivers/memory/tegra/Kconfig
@@ -32,9 +32,10 @@ config TEGRA30_EMC
 	  external memory.
 
 config TEGRA124_EMC
-	bool "NVIDIA Tegra124 External Memory Controller driver"
+	tristate "NVIDIA Tegra124 External Memory Controller driver"
 	default y
 	depends on TEGRA_MC && ARCH_TEGRA_124_SOC
+	select TEGRA124_CLK_EMC
 	help
 	  This driver is for the External Memory Controller (EMC) found on
 	  Tegra124 chips. The EMC controls the external DRAM on the board.
diff --git a/drivers/memory/tegra/tegra124-emc.c b/drivers/memory/tegra/tegra124-emc.c
index ee8ee39e98ed..edfbf6d6d357 100644
--- a/drivers/memory/tegra/tegra124-emc.c
+++ b/drivers/memory/tegra/tegra124-emc.c
@@ -9,16 +9,17 @@
 #include <linux/clk-provider.h>
 #include <linux/clk.h>
 #include <linux/clkdev.h>
+#include <linux/clk/tegra.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/io.h>
+#include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/sort.h>
 #include <linux/string.h>
 
-#include <soc/tegra/emc.h>
 #include <soc/tegra/fuse.h>
 #include <soc/tegra/mc.h>
 
@@ -562,8 +563,8 @@ static struct emc_timing *tegra_emc_find_timing(struct tegra_emc *emc,
 	return timing;
 }
 
-int tegra_emc_prepare_timing_change(struct tegra_emc *emc,
-				    unsigned long rate)
+static int tegra_emc_prepare_timing_change(struct tegra_emc *emc,
+					   unsigned long rate)
 {
 	struct emc_timing *timing = tegra_emc_find_timing(emc, rate);
 	struct emc_timing *last = &emc->last_timing;
@@ -790,8 +791,8 @@ int tegra_emc_prepare_timing_change(struct tegra_emc *emc,
 	return 0;
 }
 
-void tegra_emc_complete_timing_change(struct tegra_emc *emc,
-				      unsigned long rate)
+static void tegra_emc_complete_timing_change(struct tegra_emc *emc,
+					     unsigned long rate)
 {
 	struct emc_timing *timing = tegra_emc_find_timing(emc, rate);
 	struct emc_timing *last = &emc->last_timing;
@@ -987,6 +988,7 @@ static const struct of_device_id tegra_emc_of_match[] = {
 	{ .compatible = "nvidia,tegra132-emc" },
 	{}
 };
+MODULE_DEVICE_TABLE(of, tegra_emc_of_match);
 
 static struct device_node *
 tegra_emc_find_node_by_ram_code(struct device_node *node, u32 ram_code)
@@ -1226,9 +1228,19 @@ static int tegra_emc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, emc);
 
+	tegra124_clk_set_emc_callbacks(tegra_emc_prepare_timing_change,
+				       tegra_emc_complete_timing_change);
+
 	if (IS_ENABLED(CONFIG_DEBUG_FS))
 		emc_debugfs_init(&pdev->dev, emc);
 
+	/*
+	 * Don't allow the kernel module to be unloaded. Unloading adds some
+	 * extra complexity which doesn't really worth the effort in a case of
+	 * this driver.
+	 */
+	try_module_get(THIS_MODULE);
+
 	return 0;
 };
 
@@ -1240,9 +1252,8 @@ static struct platform_driver tegra_emc_driver = {
 		.suppress_bind_attrs = true,
 	},
 };
+module_platform_driver(tegra_emc_driver);
 
-static int tegra_emc_init(void)
-{
-	return platform_driver_register(&tegra_emc_driver);
-}
-subsys_initcall(tegra_emc_init);
+MODULE_AUTHOR("Mikko Perttunen <mperttunen@nvidia.com>");
+MODULE_DESCRIPTION("NVIDIA Tegra124 EMC driver");
+MODULE_LICENSE("GPL v2");