写一个LPC总线的master驱动

LPC总线是一种低速、低功耗的总线，常用于连接嵌入式系统中的外设。下面是一个LPC总线的master驱动的示例代码：

#include <linux/module.h>
#include <linux/types.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/delay.h>

#define LPC_IO_BASE	0x40000000	/* LPC总线基地址 */
#define LPC_SRAM_BASE	0x80000000	/* SRAM基地址 */
#define LPC_FLASH_BASE	0x90000000	/* FLASH基地址 */

/* LPC总线寄存器偏移量 */
#define LPC_IOREG_OFFSET	0x800
#define LPC_MEMREG_OFFSET	0x400

/* LPC总线寄存器定义 */
#define LPC_SC			(LPC_IO_BASE + 0x000)
#define LPC_PIN			(LPC_IO_BASE + 0x014)
#define LPC_PIN_DIR		(LPC_IO_BASE + 0x018)
#define LPC_PIN_SEL		(LPC_IO_BASE + 0x01C)
#define LPC_IRQ			(LPC_IO_BASE + 0x020)
#define LPC_IRQ_SEL		(LPC_IO_BASE + 0x024)
#define LPC_TIM_CTRL		(LPC_IO_BASE + 0x028)
#define LPC_TIM_CNT		(LPC_IO_BASE + 0x02C)
#define LPC_UART_CTRL		(LPC_IO_BASE + 0x030)
#define LPC_UART_STAT		(LPC_IO_BASE + 0x034)
#define LPC_UART_DATA		(LPC_IO_BASE + 0x038)
#define LPC_UART_BAUD		(LPC_IO_BASE + 0x03C)
#define LPC_GPIO0_DIR		(LPC_IO_BASE + 0x040)
#define LPC_GPIO0_DATA		(LPC_IO_BASE + 0x044)
#define LPC_GPIO1_DIR		(LPC_IO_BASE + 0x048)
#define LPC_GPIO1_DATA		(LPC_IO_BASE + 0x04C)
#define LPC_GPIO2_DIR		(LPC_IO_BASE + 0x050)
#define LPC_GPIO2_DATA		(LPC_IO_BASE + 0x054)
#define LPC_GPIO3_DIR		(LPC_IO_BASE + 0x058)
#define LPC_GPIO3_DATA		(LPC_IO_BASE + 0x05C)
#define LPC_MEM_CTRL		(LPC_IO_BASE + 0x080)
#define LPC_MEM_ADDR0		(LPC_IO_BASE + 0x084)
#define LPC_MEM_ADDR1		(LPC_IO_BASE + 0x088)
#define LPC_MEM_ADDR2		(LPC_IO_BASE + 0x08C)
#define LPC_MEM_ADDR3		(LPC_IO_BASE + 0x090)
#define LPC_IOREG_CTRL		(LPC_IO_BASE + LPC_IOREG_OFFSET)
#define LPC_IOREG_DATA		(LPC_IO_BASE + LPC_IOREG_OFFSET + 4)
#define LPC_MEMREG_CTRL		(LPC_IO_BASE + LPC_MEMREG_OFFSET)
#define LPC_MEMREG_DATA		(LPC_IO_BASE + LPC_MEMREG_OFFSET + 4)

/* 定义LPC总线支持的访问类型 */
enum lpc_access_type {
	LPCT_IO = 0,	/* I/O访问 */
	LPCT_MEM = 1,	/* 存储器访问 */
};

/* 定义LPC总线master驱动结构体 */
struct lpc_master_driver {
	struct device_driver driver;
	enum lpc_access_type access_type;
};

static int lpc_master_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct resource *res;
	struct lpc_master_driver *driver;
	void __iomem *base;
	u32 val;

	/* 获取LPC总线信息 */
	driver = dev_get_drvdata(dev);
	if (!driver) {
		dev_err(dev, "no driver data\n");
		return -EINVAL;
	}

	/* 获取LPC总线基地址 */
	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		dev_err(dev, "no LPC base address\n");
		return -ENODEV;
	}
	base = devm_ioremap_resource(dev, res);
	if (IS_ERR(base)) {
		dev_err(dev, "failed to ioremap LPC base address\n");
		return PTR_ERR(base);
	}

	/* 初始化LPC总线控制寄存器 */
	val = readl(base + LPC_IOREG_CTRL);
	val &= ~(0x3 << 2);	/* 清除访问类型位 */
	val |= (driver->access_type << 2);	/* 设置访问类型 */
	writel(val, base + LPC_IOREG_CTRL);

	return 0;
}

static int lpc_master_remove(struct platform_device *pdev)
{
	return 0;
}

/* 定义LPC总线master驱动匹配表 */
static const struct of_device_id lpc_master_of_match[] = {
	{ .compatible = "lpc-master", .data = &(struct lpc_master_driver){
		.access_type = LPCT_IO,
	} },
	{ .compatible = "lpc-master-mem", .data = &(struct lpc_master_driver){
		.access_type = LPCT_MEM,
	} },
	{},
};
MODULE_DEVICE_TABLE(of, lpc_master_of_match);

/* 定义LPC总线master驱动结构体 */
static struct platform_driver lpc_master_driver = {
	.driver = {
		.name = "lpc-master",
		.of_match_table = lpc_master_of_match,
	},
	.probe = lpc_master_probe,
	.remove = lpc_master_remove,
};

/* 初始化LPC总线master驱动 */
static int __init lpc_master_init(void)
{
	return platform_driver_register(&lpc_master_driver);
}
module_init(lpc_master_init);

/* 卸载LPC总线master驱动 */
static void __exit lpc_master_exit(void)
{
	platform_driver_unregister(&lpc_master_driver);
}
module_exit(lpc_master_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("LPC Master Driver");

这个驱动使用了Platform Driver框架，可以在设备树中定义LPC总线master驱动节点，例如：

lpc_master {
	compatible = "lpc-master";
};

或者：

lpc_master_mem {
	compatible = "lpc-master-mem";
};

这两个驱动分别用于I/O访问和存储器访问，可以根据需要选择。驱动会根据设备树的配置自动选择访问类型，并初始化LPC总线控制寄存器。