drivers/rtc/rtc-gamecube.c - SHIFTPHONES/mainline/linux - Gitiles

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Nintendo GameCube, Wii and Wii U RTC driver
  *
  * This driver is for the MX23L4005, more specifically its real-time clock and
  * SRAM storage.  The value returned by the RTC counter must be added with the
  * offset stored in a bias register in SRAM (on the GameCube and Wii) or in
  * /config/rtc.xml (on the Wii U).  The latter being very impractical to access
  * from Linux, this driver assumes the bootloader has read it and stored it in
  * SRAM like for the other two consoles.
  *
  * This device sits on a bus named EXI (which is similar to SPI), channel 0,
  * device 1.  This driver assumes no other user of the EXI bus, which is
  * currently the case but would have to be reworked to add support for other
  * GameCube hardware exposed on this bus.
  *
  * References:
  * - https://wiiubrew.org/wiki/Hardware/RTC
  * - https://wiibrew.org/wiki/MX23L4005
  *
  * Copyright (C) 2018 rw-r-r-0644
  * Copyright (C) 2021 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
  *
  * Based on rtc-gcn.c
  * Copyright (C) 2004-2009 The GameCube Linux Team
  * Copyright (C) 2005,2008,2009 Albert Herranz
  * Based on gamecube_time.c from Torben Nielsen.
  */

 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/rtc.h>
 #include <linux/time.h>

 /* EXI registers */
 #define EXICSR	0
 #define EXICR	12
 #define EXIDATA	16

 /* EXI register values */
 #define EXICSR_DEV		0x380
 	#define EXICSR_DEV1	0x100
 #define EXICSR_CLK		0x070
 	#define EXICSR_CLK_1MHZ	0x000
 	#define EXICSR_CLK_2MHZ	0x010
 	#define EXICSR_CLK_4MHZ	0x020
 	#define EXICSR_CLK_8MHZ	0x030
 	#define EXICSR_CLK_16MHZ 0x040
 	#define EXICSR_CLK_32MHZ 0x050
 #define EXICSR_INT		0x008
 	#define EXICSR_INTSET	0x008

 #define EXICR_TSTART		0x001
 #define EXICR_TRSMODE		0x002
 	#define EXICR_TRSMODE_IMM 0x000
 #define EXICR_TRSTYPE		0x00C
 	#define EXICR_TRSTYPE_R	0x000
 	#define EXICR_TRSTYPE_W	0x004
 #define EXICR_TLEN		0x030
 	#define EXICR_TLEN32	0x030

 /* EXI registers values to access the RTC */
 #define RTC_EXICSR	(EXICSR_DEV1 | EXICSR_CLK_8MHZ | EXICSR_INTSET)
 #define RTC_EXICR_W	(EXICR_TSTART | EXICR_TRSMODE_IMM | EXICR_TRSTYPE_W | EXICR_TLEN32)
 #define RTC_EXICR_R	(EXICR_TSTART | EXICR_TRSMODE_IMM | EXICR_TRSTYPE_R | EXICR_TLEN32)
 #define RTC_EXIDATA_W	0x80000000

 /* RTC registers */
 #define RTC_COUNTER	0x200000
 #define RTC_SRAM	0x200001
 #define RTC_SRAM_BIAS	0x200004
 #define RTC_SNAPSHOT	0x204000
 #define RTC_ONTMR	0x210000
 #define RTC_OFFTMR	0x210001
 #define RTC_TEST0	0x210004
 #define RTC_TEST1	0x210005
 #define RTC_TEST2	0x210006
 #define RTC_TEST3	0x210007
 #define RTC_CONTROL0	0x21000c
 #define RTC_CONTROL1	0x21000d

 /* RTC flags */
 #define RTC_CONTROL0_UNSTABLE_POWER	0x00000800
 #define RTC_CONTROL0_LOW_BATTERY	0x00000200

 struct priv {
 	struct regmap *regmap;
 	void __iomem *iob;
 	u32 rtc_bias;
 };

 static int exi_read(void *context, u32 reg, u32 *data)
 {
 	struct priv *d = (struct priv *)context;
 	void __iomem *iob = d->iob;

 	/* The spin loops here loop about 15~16 times each, so there is no need
 	 * to use a more expensive sleep method.
 	 */

 	/* Write register offset */
 	iowrite32be(RTC_EXICSR, iob + EXICSR);
 	iowrite32be(reg << 8, iob + EXIDATA);
 	iowrite32be(RTC_EXICR_W, iob + EXICR);
 	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
 		cpu_relax();

 	/* Read data */
 	iowrite32be(RTC_EXICSR, iob + EXICSR);
 	iowrite32be(RTC_EXICR_R, iob + EXICR);
 	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
 		cpu_relax();
 	*data = ioread32be(iob + EXIDATA);

 	/* Clear channel parameters */
 	iowrite32be(0, iob + EXICSR);

 	return 0;
 }

 static int exi_write(void *context, u32 reg, u32 data)
 {
 	struct priv *d = (struct priv *)context;
 	void __iomem *iob = d->iob;

 	/* The spin loops here loop about 15~16 times each, so there is no need
 	 * to use a more expensive sleep method.
 	 */

 	/* Write register offset */
 	iowrite32be(RTC_EXICSR, iob + EXICSR);
 	iowrite32be(RTC_EXIDATA_W | (reg << 8), iob + EXIDATA);
 	iowrite32be(RTC_EXICR_W, iob + EXICR);
 	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
 		cpu_relax();

 	/* Write data */
 	iowrite32be(RTC_EXICSR, iob + EXICSR);
 	iowrite32be(data, iob + EXIDATA);
 	iowrite32be(RTC_EXICR_W, iob + EXICR);
 	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
 		cpu_relax();

 	/* Clear channel parameters */
 	iowrite32be(0, iob + EXICSR);

 	return 0;
 }

 static const struct regmap_bus exi_bus = {
 	/* TODO: is that true?  Not that it matters here, but still. */
 	.fast_io = true,
 	.reg_read = exi_read,
 	.reg_write = exi_write,
 };

 static int gamecube_rtc_read_time(struct device *dev, struct rtc_time *t)
 {
 	struct priv *d = dev_get_drvdata(dev);
 	int ret;
 	u32 counter;
 	time64_t timestamp;

 	ret = regmap_read(d->regmap, RTC_COUNTER, &counter);
 	if (ret)
 		return ret;

 	/* Add the counter and the bias to obtain the timestamp */
 	timestamp = (time64_t)d->rtc_bias + counter;
 	rtc_time64_to_tm(timestamp, t);

 	return 0;
 }

 static int gamecube_rtc_set_time(struct device *dev, struct rtc_time *t)
 {
 	struct priv *d = dev_get_drvdata(dev);
 	time64_t timestamp;

 	/* Subtract the timestamp and the bias to obtain the counter value */
 	timestamp = rtc_tm_to_time64(t);
 	return regmap_write(d->regmap, RTC_COUNTER, timestamp - d->rtc_bias);
 }

 static int gamecube_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 {
 	struct priv *d = dev_get_drvdata(dev);
 	int value;
 	int control0;
 	int ret;

 	switch (cmd) {
 	case RTC_VL_READ:
 		ret = regmap_read(d->regmap, RTC_CONTROL0, &control0);
 		if (ret)
 			return ret;

 		value = 0;
 		if (control0 & RTC_CONTROL0_UNSTABLE_POWER)
 			value |= RTC_VL_DATA_INVALID;
 		if (control0 & RTC_CONTROL0_LOW_BATTERY)
 			value |= RTC_VL_BACKUP_LOW;
 		return put_user(value, (unsigned int __user *)arg);

 	default:
 		return -ENOIOCTLCMD;
 	}
 }

 static const struct rtc_class_ops gamecube_rtc_ops = {
 	.read_time	= gamecube_rtc_read_time,
 	.set_time	= gamecube_rtc_set_time,
 	.ioctl		= gamecube_rtc_ioctl,
 };

 static int gamecube_rtc_read_offset_from_sram(struct priv *d)
 {
 	struct device_node *np;
 	int ret;
 	struct resource res;
 	void __iomem *hw_srnprot;
 	u32 old;

 	np = of_find_compatible_node(NULL, NULL, "nintendo,latte-srnprot");
 	if (!np)
 		np = of_find_compatible_node(NULL, NULL,
 					     "nintendo,hollywood-srnprot");
 	if (!np) {
 		pr_info("HW_SRNPROT not found, assuming a GameCube\n");
 		return regmap_read(d->regmap, RTC_SRAM_BIAS, &d->rtc_bias);
 	}

 	ret = of_address_to_resource(np, 0, &res);
 	if (ret) {
 		pr_err("no io memory range found\n");
 		return -1;
 	}

 	hw_srnprot = ioremap(res.start, resource_size(&res));
 	old = ioread32be(hw_srnprot);

 	/* TODO: figure out why we use this magic constant.  I obtained it by
 	 * reading the leftover value after boot, after IOSU already ran.
 	 *
 	 * On my Wii U, setting this register to 1 prevents the console from
 	 * rebooting properly, so wiiubrew.org must be missing something.
 	 *
 	 * See https://wiiubrew.org/wiki/Hardware/Latte_registers
 	 */
 	if (old != 0x7bf)
 		iowrite32be(0x7bf, hw_srnprot);

 	/* Get the offset from RTC SRAM.
 	 *
 	 * Its default location on the GameCube and on the Wii is in the SRAM,
 	 * while on the Wii U the bootloader needs to fill it with the contents
 	 * of /config/rtc.xml on the SLC (the eMMC).  We don’t do that from
 	 * Linux since it requires implementing a proprietary filesystem and do
 	 * file decryption, instead we require the bootloader to fill the same
 	 * SRAM address as on previous consoles.
 	 */
 	ret = regmap_read(d->regmap, RTC_SRAM_BIAS, &d->rtc_bias);
 	if (ret) {
 		pr_err("failed to get the RTC bias\n");
 		return -1;
 	}

 	/* Reset SRAM access to how it was before, our job here is done. */
 	if (old != 0x7bf)
 		iowrite32be(old, hw_srnprot);
 	iounmap(hw_srnprot);

 	return 0;
 }

 static const struct regmap_range rtc_rd_ranges[] = {
 	regmap_reg_range(0x200000, 0x200010),
 	regmap_reg_range(0x204000, 0x204000),
 	regmap_reg_range(0x210000, 0x210001),
 	regmap_reg_range(0x210004, 0x210007),
 	regmap_reg_range(0x21000c, 0x21000d),
 };

 static const struct regmap_access_table rtc_rd_regs = {
 	.yes_ranges =	rtc_rd_ranges,
 	.n_yes_ranges =	ARRAY_SIZE(rtc_rd_ranges),
 };

 static const struct regmap_range rtc_wr_ranges[] = {
 	regmap_reg_range(0x200000, 0x200010),
 	regmap_reg_range(0x204000, 0x204000),
 	regmap_reg_range(0x210000, 0x210001),
 	regmap_reg_range(0x21000d, 0x21000d),
 };

 static const struct regmap_access_table rtc_wr_regs = {
 	.yes_ranges =	rtc_wr_ranges,
 	.n_yes_ranges =	ARRAY_SIZE(rtc_wr_ranges),
 };

 static const struct regmap_config gamecube_rtc_regmap_config = {
 	.reg_bits = 24,
 	.val_bits = 32,
 	.rd_table = &rtc_rd_regs,
 	.wr_table = &rtc_wr_regs,
 	.max_register = 0x21000d,
 	.name = "gamecube-rtc",
 };

 static int gamecube_rtc_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct rtc_device *rtc;
 	struct priv *d;
 	int ret;

 	d = devm_kzalloc(dev, sizeof(struct priv), GFP_KERNEL);
 	if (!d)
 		return -ENOMEM;

 	d->iob = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(d->iob))
 		return PTR_ERR(d->iob);

 	d->regmap = devm_regmap_init(dev, &exi_bus, d,
 				     &gamecube_rtc_regmap_config);
 	if (IS_ERR(d->regmap))
 		return PTR_ERR(d->regmap);

 	ret = gamecube_rtc_read_offset_from_sram(d);
 	if (ret)
 		return ret;
 	dev_dbg(dev, "SRAM bias: 0x%x", d->rtc_bias);

 	dev_set_drvdata(dev, d);

 	rtc = devm_rtc_allocate_device(dev);
 	if (IS_ERR(rtc))
 		return PTR_ERR(rtc);

 	/* We can represent further than that, but it depends on the stored
 	 * bias and we can’t modify it persistently on all supported consoles,
 	 * so here we pretend to be limited to 2106.
 	 */
 	rtc->range_min = 0;
 	rtc->range_max = U32_MAX;
 	rtc->ops = &gamecube_rtc_ops;

 	devm_rtc_register_device(rtc);

 	return 0;
 }

 static const struct of_device_id gamecube_rtc_of_match[] = {
 	{.compatible = "nintendo,latte-exi" },
 	{.compatible = "nintendo,hollywood-exi" },
 	{.compatible = "nintendo,flipper-exi" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, gamecube_rtc_of_match);

 static struct platform_driver gamecube_rtc_driver = {
 	.probe		= gamecube_rtc_probe,
 	.driver		= {
 		.name	= "rtc-gamecube",
 		.of_match_table	= gamecube_rtc_of_match,
 	},
 };
 module_platform_driver(gamecube_rtc_driver);

 MODULE_AUTHOR("Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>");
 MODULE_DESCRIPTION("Nintendo GameCube, Wii and Wii U RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Nintendo GameCube, Wii and Wii U RTC driver
	*
	* This driver is for the MX23L4005, more specifically its real-time clock and
	* SRAM storage. The value returned by the RTC counter must be added with the
	* offset stored in a bias register in SRAM (on the GameCube and Wii) or in
	* /config/rtc.xml (on the Wii U). The latter being very impractical to access
	* from Linux, this driver assumes the bootloader has read it and stored it in
	* SRAM like for the other two consoles.
	*
	* This device sits on a bus named EXI (which is similar to SPI), channel 0,
	* device 1. This driver assumes no other user of the EXI bus, which is
	* currently the case but would have to be reworked to add support for other
	* GameCube hardware exposed on this bus.
	*
	* References:
	* - https://wiiubrew.org/wiki/Hardware/RTC
	* - https://wiibrew.org/wiki/MX23L4005
	*
	* Copyright (C) 2018 rw-r-r-0644
	* Copyright (C) 2021 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
	*
	* Based on rtc-gcn.c
	* Copyright (C) 2004-2009 The GameCube Linux Team
	* Copyright (C) 2005,2008,2009 Albert Herranz
	* Based on gamecube_time.c from Torben Nielsen.
	*/

	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_address.h>
	#include <linux/platform_device.h>
	#include <linux/regmap.h>
	#include <linux/rtc.h>
	#include <linux/time.h>

	/* EXI registers */
	#define EXICSR 0
	#define EXICR 12
	#define EXIDATA 16

	/* EXI register values */
	#define EXICSR_DEV 0x380
	#define EXICSR_DEV1 0x100
	#define EXICSR_CLK 0x070
	#define EXICSR_CLK_1MHZ 0x000
	#define EXICSR_CLK_2MHZ 0x010
	#define EXICSR_CLK_4MHZ 0x020
	#define EXICSR_CLK_8MHZ 0x030
	#define EXICSR_CLK_16MHZ 0x040
	#define EXICSR_CLK_32MHZ 0x050
	#define EXICSR_INT 0x008
	#define EXICSR_INTSET 0x008

	#define EXICR_TSTART 0x001
	#define EXICR_TRSMODE 0x002
	#define EXICR_TRSMODE_IMM 0x000
	#define EXICR_TRSTYPE 0x00C
	#define EXICR_TRSTYPE_R 0x000
	#define EXICR_TRSTYPE_W 0x004
	#define EXICR_TLEN 0x030
	#define EXICR_TLEN32 0x030

	/* EXI registers values to access the RTC */
	#define RTC_EXICSR (EXICSR_DEV1 \| EXICSR_CLK_8MHZ \| EXICSR_INTSET)
	#define RTC_EXICR_W (EXICR_TSTART \| EXICR_TRSMODE_IMM \| EXICR_TRSTYPE_W \| EXICR_TLEN32)
	#define RTC_EXICR_R (EXICR_TSTART \| EXICR_TRSMODE_IMM \| EXICR_TRSTYPE_R \| EXICR_TLEN32)
	#define RTC_EXIDATA_W 0x80000000

	/* RTC registers */
	#define RTC_COUNTER 0x200000
	#define RTC_SRAM 0x200001
	#define RTC_SRAM_BIAS 0x200004
	#define RTC_SNAPSHOT 0x204000
	#define RTC_ONTMR 0x210000
	#define RTC_OFFTMR 0x210001
	#define RTC_TEST0 0x210004
	#define RTC_TEST1 0x210005
	#define RTC_TEST2 0x210006
	#define RTC_TEST3 0x210007
	#define RTC_CONTROL0 0x21000c
	#define RTC_CONTROL1 0x21000d

	/* RTC flags */
	#define RTC_CONTROL0_UNSTABLE_POWER 0x00000800
	#define RTC_CONTROL0_LOW_BATTERY 0x00000200

	struct priv {
	struct regmap *regmap;
	void __iomem *iob;
	u32 rtc_bias;
	};

	static int exi_read(void context, u32 reg, u32 data)
	{
	struct priv d = (struct priv )context;
	void __iomem *iob = d->iob;

	/* The spin loops here loop about 15~16 times each, so there is no need
	* to use a more expensive sleep method.
	*/

	/* Write register offset */
	iowrite32be(RTC_EXICSR, iob + EXICSR);
	iowrite32be(reg << 8, iob + EXIDATA);
	iowrite32be(RTC_EXICR_W, iob + EXICR);
	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
	cpu_relax();

	/* Read data */
	iowrite32be(RTC_EXICSR, iob + EXICSR);
	iowrite32be(RTC_EXICR_R, iob + EXICR);
	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
	cpu_relax();
	*data = ioread32be(iob + EXIDATA);

	/* Clear channel parameters */
	iowrite32be(0, iob + EXICSR);

	return 0;
	}

	static int exi_write(void *context, u32 reg, u32 data)
	{
	struct priv d = (struct priv )context;
	void __iomem *iob = d->iob;

	/* The spin loops here loop about 15~16 times each, so there is no need
	* to use a more expensive sleep method.
	*/

	/* Write register offset */
	iowrite32be(RTC_EXICSR, iob + EXICSR);
	iowrite32be(RTC_EXIDATA_W \| (reg << 8), iob + EXIDATA);
	iowrite32be(RTC_EXICR_W, iob + EXICR);
	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
	cpu_relax();

	/* Write data */
	iowrite32be(RTC_EXICSR, iob + EXICSR);
	iowrite32be(data, iob + EXIDATA);
	iowrite32be(RTC_EXICR_W, iob + EXICR);
	while (!(ioread32be(iob + EXICSR) & EXICSR_INTSET))
	cpu_relax();

	/* Clear channel parameters */
	iowrite32be(0, iob + EXICSR);

	return 0;
	}

	static const struct regmap_bus exi_bus = {
	/* TODO: is that true? Not that it matters here, but still. */
	.fast_io = true,
	.reg_read = exi_read,
	.reg_write = exi_write,
	};

	static int gamecube_rtc_read_time(struct device dev, struct rtc_time t)
	{
	struct priv *d = dev_get_drvdata(dev);
	int ret;
	u32 counter;
	time64_t timestamp;

	ret = regmap_read(d->regmap, RTC_COUNTER, &counter);
	if (ret)
	return ret;

	/* Add the counter and the bias to obtain the timestamp */
	timestamp = (time64_t)d->rtc_bias + counter;
	rtc_time64_to_tm(timestamp, t);

	return 0;
	}

	static int gamecube_rtc_set_time(struct device dev, struct rtc_time t)
	{
	struct priv *d = dev_get_drvdata(dev);
	time64_t timestamp;

	/* Subtract the timestamp and the bias to obtain the counter value */
	timestamp = rtc_tm_to_time64(t);
	return regmap_write(d->regmap, RTC_COUNTER, timestamp - d->rtc_bias);
	}

	static int gamecube_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
	{
	struct priv *d = dev_get_drvdata(dev);
	int value;
	int control0;
	int ret;

	switch (cmd) {
	case RTC_VL_READ:
	ret = regmap_read(d->regmap, RTC_CONTROL0, &control0);
	if (ret)
	return ret;

	value = 0;
	if (control0 & RTC_CONTROL0_UNSTABLE_POWER)
	value \|= RTC_VL_DATA_INVALID;
	if (control0 & RTC_CONTROL0_LOW_BATTERY)
	value \|= RTC_VL_BACKUP_LOW;
	return put_user(value, (unsigned int __user *)arg);

	default:
	return -ENOIOCTLCMD;
	}
	}

	static const struct rtc_class_ops gamecube_rtc_ops = {
	.read_time = gamecube_rtc_read_time,
	.set_time = gamecube_rtc_set_time,
	.ioctl = gamecube_rtc_ioctl,
	};

	static int gamecube_rtc_read_offset_from_sram(struct priv *d)
	{
	struct device_node *np;
	int ret;
	struct resource res;
	void __iomem *hw_srnprot;
	u32 old;

	np = of_find_compatible_node(NULL, NULL, "nintendo,latte-srnprot");
	if (!np)
	np = of_find_compatible_node(NULL, NULL,
	"nintendo,hollywood-srnprot");
	if (!np) {
	pr_info("HW_SRNPROT not found, assuming a GameCube\n");
	return regmap_read(d->regmap, RTC_SRAM_BIAS, &d->rtc_bias);
	}

	ret = of_address_to_resource(np, 0, &res);
	if (ret) {
	pr_err("no io memory range found\n");
	return -1;
	}

	hw_srnprot = ioremap(res.start, resource_size(&res));
	old = ioread32be(hw_srnprot);

	/* TODO: figure out why we use this magic constant. I obtained it by
	* reading the leftover value after boot, after IOSU already ran.
	*
	* On my Wii U, setting this register to 1 prevents the console from
	* rebooting properly, so wiiubrew.org must be missing something.
	*
	* See https://wiiubrew.org/wiki/Hardware/Latte_registers
	*/
	if (old != 0x7bf)
	iowrite32be(0x7bf, hw_srnprot);

	/* Get the offset from RTC SRAM.
	*
	* Its default location on the GameCube and on the Wii is in the SRAM,
	* while on the Wii U the bootloader needs to fill it with the contents
	* of /config/rtc.xml on the SLC (the eMMC). We don’t do that from
	* Linux since it requires implementing a proprietary filesystem and do
	* file decryption, instead we require the bootloader to fill the same
	* SRAM address as on previous consoles.
	*/
	ret = regmap_read(d->regmap, RTC_SRAM_BIAS, &d->rtc_bias);
	if (ret) {
	pr_err("failed to get the RTC bias\n");
	return -1;
	}

	/* Reset SRAM access to how it was before, our job here is done. */
	if (old != 0x7bf)
	iowrite32be(old, hw_srnprot);
	iounmap(hw_srnprot);

	return 0;
	}

	static const struct regmap_range rtc_rd_ranges[] = {
	regmap_reg_range(0x200000, 0x200010),
	regmap_reg_range(0x204000, 0x204000),
	regmap_reg_range(0x210000, 0x210001),
	regmap_reg_range(0x210004, 0x210007),
	regmap_reg_range(0x21000c, 0x21000d),
	};

	static const struct regmap_access_table rtc_rd_regs = {
	.yes_ranges = rtc_rd_ranges,
	.n_yes_ranges = ARRAY_SIZE(rtc_rd_ranges),
	};

	static const struct regmap_range rtc_wr_ranges[] = {
	regmap_reg_range(0x200000, 0x200010),
	regmap_reg_range(0x204000, 0x204000),
	regmap_reg_range(0x210000, 0x210001),
	regmap_reg_range(0x21000d, 0x21000d),
	};

	static const struct regmap_access_table rtc_wr_regs = {
	.yes_ranges = rtc_wr_ranges,
	.n_yes_ranges = ARRAY_SIZE(rtc_wr_ranges),
	};

	static const struct regmap_config gamecube_rtc_regmap_config = {
	.reg_bits = 24,
	.val_bits = 32,
	.rd_table = &rtc_rd_regs,
	.wr_table = &rtc_wr_regs,
	.max_register = 0x21000d,
	.name = "gamecube-rtc",
	};

	static int gamecube_rtc_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct rtc_device *rtc;
	struct priv *d;
	int ret;

	d = devm_kzalloc(dev, sizeof(struct priv), GFP_KERNEL);
	if (!d)
	return -ENOMEM;

	d->iob = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(d->iob))
	return PTR_ERR(d->iob);

	d->regmap = devm_regmap_init(dev, &exi_bus, d,
	&gamecube_rtc_regmap_config);
	if (IS_ERR(d->regmap))
	return PTR_ERR(d->regmap);

	ret = gamecube_rtc_read_offset_from_sram(d);
	if (ret)
	return ret;
	dev_dbg(dev, "SRAM bias: 0x%x", d->rtc_bias);

	dev_set_drvdata(dev, d);

	rtc = devm_rtc_allocate_device(dev);
	if (IS_ERR(rtc))
	return PTR_ERR(rtc);

	/* We can represent further than that, but it depends on the stored
	* bias and we can’t modify it persistently on all supported consoles,
	* so here we pretend to be limited to 2106.
	*/
	rtc->range_min = 0;
	rtc->range_max = U32_MAX;
	rtc->ops = &gamecube_rtc_ops;

	devm_rtc_register_device(rtc);

	return 0;
	}

	static const struct of_device_id gamecube_rtc_of_match[] = {
	{.compatible = "nintendo,latte-exi" },
	{.compatible = "nintendo,hollywood-exi" },
	{.compatible = "nintendo,flipper-exi" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, gamecube_rtc_of_match);

	static struct platform_driver gamecube_rtc_driver = {
	.probe = gamecube_rtc_probe,
	.driver = {
	.name = "rtc-gamecube",
	.of_match_table = gamecube_rtc_of_match,
	},
	};
	module_platform_driver(gamecube_rtc_driver);

	MODULE_AUTHOR("Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>");
	MODULE_DESCRIPTION("Nintendo GameCube, Wii and Wii U RTC driver");
	MODULE_LICENSE("GPL");