16c750_support.h

#define UART_RHR_REG	0x000
#define UART_THR_REG	0x000
#define UART_IER_REG	0x004
#define UART_IIR_REG	0x008
#define UART_FCR_REG	0x008
#define UART_LCR_REG	0x00C
#define UART_MCR_REG	0x010
#define UART_LSR_REG	0x014
#define UART_MSR_REG	0x018
#define UART_SPR_REG	0x01C
#define UART_MDR1_REG	0x020
#define UART_MDR2_REG	0x024
#define UART_MDR3_REG	0x080
#define UART_SYSC_REG	0x054
#define UART_SYSS_REG	0x058
#define UART_RXFIFO_LVL_REG	0x064
#define UART_TXFIFO_LVL_REG	0x068
#define UART_DLL_REG	0x100
#define UART_DLH_REG	0x104
#define UART_EFR_REG	0x208

// This function writes a 16-bit value to the UART register with byte offset reg_offset 
void write_uart_reg_raw (u32 reg_offset, u16 value);

// This function reads a 16-bit value from the UART register with the byte offset reg_offset
u16 read_uart_reg_raw (u32 reg_offset);

static u16 cached_lcr = 0;

void write_uart_reg (u32 reg, u16 value)
{
        u16 lcr_selector_index = (reg / 256) % 3;
        u16 reg_offset = (reg % 256);

        if (lcr_selector_index == 1)
                write_uart_reg_raw (UART_LCR_REG, cached_lcr | 0x80);
        else if (lcr_selector_index == 2)
                write_uart_reg_raw (UART_LCR_REG, 0xBF);

        write_uart_reg_raw (reg_offset, value);
        if (reg_offset == UART_LCR_REG)
                cached_lcr = value;

        if (lcr_selector_index != 0)
                write_uart_reg_raw (UART_LCR_REG, cached_lcr);
}

u16 read_uart_reg (u32 reg)
{
        u16 value = 0;
        u16 lcr_selector_index = (reg / 256) % 3;
        u16 reg_offset = (reg % 256);

        if (lcr_selector_index == 1)
                write_uart_reg_raw (UART_LCR_REG, cached_lcr | 0x80);
        else if (lcr_selector_index == 2)
                write_uart_reg_raw (UART_LCR_REG, 0xBF);

        value = read_uart_reg_raw (reg_offset);

        if (lcr_selector_index != 0)
                write_uart_reg_raw (UART_LCR_REG, cached_lcr);

        return value;
}

void init_uart_reg (void)
{
        write_uart_reg_raw (UART_LCR_REG, cached_lcr);
}