A problem about serial port on bochs, only 5 bits output

[whereware]

The following is the outputs of 'xxd' command.

correct output by qemu | incorrect output by bochs
00000000: 0c0f 0104 0e03 1a11 1912 001c 0009 0e06 │ 00000000: 6c6f 6164 2e63 3a31 3932 207c 2049 6e66
00000010: 0f00 1c00 0f13 0c0f 0104 0512 1f0d 0109 │ 00000010: 6f20 7c20 6f73 6c6f 6164 6572 5f6d 6169
00000020: 0e0c 0005 0e14 0512 0a0c 0f01 040e 031a │ 00000020: 6e2c 2065 6e74 6572 0a6c 6f61 642e 633a

it seems that bits[7:5] are set to 0

my serial port initialization code :

Code: Select all

#define UART_COM1 (0x3F8)
#define UART_COM2 (0x2F8)

#define UART_DATA (0x0)     // data register.
#define UART_DIVL (0x0)     // with DLAB set to 1, least significant byte of  
                            // divisior for baud rate.

#define UART_DIVM (0x1)     // with DLAB set to 1, most significant byte.   
#define UART_INTE (0x1)     // interrupt Enable register

#define UART_INTI (0x2)     // interrupt identification 

#define UART_FCRL (0x2)     // FIFO control registers

#define UART_LCRL (0x3)     // Line Control Register
                            // most significant bit of this register is DLAB

#define UART_MCRL (0x4)     // Modern Control Register

void uart_init()
{
    x86_outb(UART_COM1 + UART_INTE, 0x00); // disable all intrrupt
    x86_outb(UART_COM1 + UART_LCRL, 0x80); // Set DLAB
    x86_outb(UART_COM1 + UART_DIVL, 0x03); // set least significant byte of divisor to 0x03
    x86_outb(UART_COM1 + UART_DIVM, 0x00); // set most significant byte of divisor to 0
    x86_outb(UART_COM1 + UART_LCRL, 0x03); // 8 bits, no parity, one stop bit
    x86_outb(UART_COM1 + UART_FCRL, 0xc7); // FIFO
    x86_outb(UART_COM1 + UART_MCRL, 0x0b); // IRQs enabled, RTS/DSR set
}

config file of bochs:

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ata0-master: type=disk, path=build/img.bin
boot: disk
com1: enabled=1, mode=file, dev=com1.log
log: bochs.log
gdbstub: enabled=1

I found a post about the same problem viewtopic.php?f=1&t=30753 , but the solutions there did not work.

Does any one have suggesions? thanks in advance

[crosssans]

Just out of curiosity, could you show the source code for the `x86_outb` function?

[whereware]

Just out of curiosity, could you show the source code for the `x86_outb` function?

that is it, intel syntax with "-masm=intel" in gcc compile flags

Code: Select all

static inline void x86_outb(uint16_t port, uint8_t data)
{
    __asm__ volatile ("out %1, %0;" : : "a"(data), "d"(port));
}

[crosssans]

Can you also show what code is calling the `uart_init` function? (or even better: can you just post your entire project on GitLab/GitHub?)