ARM: s3c24xx: pass pointer to clk driver via platform data

Passing pointers directly as platform data is fragile and undocumented.
Better to create a platform data structure which explicitly documents
what is passed to the driver.
Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200806182059.2431-6-krzk@kernel.org

MAINTAINERS

@@ -15305,6 +15305,7 @@ F:	Documentation/devicetree/bindings/clock/samsung,s5p*
 F:	drivers/clk/samsung/
 F:	include/dt-bindings/clock/exynos*.h
 F:	include/linux/clk/samsung.h
+F:	include/linux/platform_data/clk-s3c2410.h
 
 SAMSUNG SPI DRIVERS
 M:	Kukjin Kim <kgene@kernel.org>

arch/arm/mach-s3c24xx/common.c

@@ -17,6 +17,7 @@
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/io.h>
+#include <linux/platform_data/clk-s3c2410.h>
 #include <linux/platform_data/dma-s3c24xx.h>
 #include <linux/dmaengine.h>
 #include <linux/clk/samsung.h>
@@ -663,13 +664,17 @@ static struct resource s3c2410_dclk_resource[] = {
 	[0] = DEFINE_RES_MEM(0x56000084, 0x4),
 };
 
+static struct s3c2410_clk_platform_data s3c_clk_platform_data = {
+	.modify_misccr = s3c2410_modify_misccr,
+};
+
 struct platform_device s3c2410_device_dclk = {
 	.name		= "s3c2410-dclk",
 	.id		= 0,
 	.num_resources	= ARRAY_SIZE(s3c2410_dclk_resource),
 	.resource	= s3c2410_dclk_resource,
 	.dev		= {
-		.platform_data = s3c2410_modify_misccr,
+		.platform_data = &s3c_clk_platform_data,
 	},
 };
 #endif

drivers/clk/samsung/clk-s3c2410-dclk.c

@@ -11,6 +11,7 @@
 #include <linux/clk-provider.h>
 #include <linux/io.h>
 #include <linux/platform_device.h>
+#include <linux/platform_data/clk-s3c2410.h>
 #include <linux/module.h>
 #include "clk.h"
 
@@ -89,10 +90,14 @@ static struct clk_hw *s3c24xx_register_clkout(struct device *dev,
 		const char *name, const char **parent_names, u8 num_parents,
 		u8 shift, u32 mask)
 {
+	struct s3c2410_clk_platform_data *pdata = dev_get_platdata(dev);
 	struct s3c24xx_clkout *clkout;
 	struct clk_init_data init;
 	int ret;
 
+	if (!pdata)
+		return ERR_PTR(-EINVAL);
+
 	/* allocate the clkout */
 	clkout = kzalloc(sizeof(*clkout), GFP_KERNEL);
 	if (!clkout)
@@ -107,7 +112,7 @@ static struct clk_hw *s3c24xx_register_clkout(struct device *dev,
 	clkout->shift = shift;
 	clkout->mask = mask;
 	clkout->hw.init = &init;
-	clkout->modify_misccr = dev->platform_data;
+	clkout->modify_misccr = pdata->modify_misccr;
 
 	ret = clk_hw_register(dev, &clkout->hw);
 	if (ret)

include/linux/platform_data/clk-s3c2410.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2020 Krzysztof Kozlowski <krzk@kernel.org>
+ */
+
+#ifndef __LINUX_PLATFORM_DATA_CLK_S3C2410_H_
+#define __LINUX_PLATFORM_DATA_CLK_S3C2410_H_
+
+/**
+ * struct s3c2410_clk_platform_data - platform data for S3C2410 clock driver
+ *
+ * @modify_misccr: Function to modify the MISCCR and return the new value
+ */
+struct s3c2410_clk_platform_data {
+	unsigned int (*modify_misccr)(unsigned int clr, unsigned int chg);
+};
+
+#endif /* __LINUX_PLATFORM_DATA_CLK_S3C2410_H_ */
+