Re: Base Baud Calculation

Aman,

At 03:57 AM 11/3/2002, you wrote:

 How is the base_baud in linux for PPC 440GP calculated?.

Here is the piece of code I use on our custom 440GP board (works also on
Ebony):

static void __init XXXXXXX_serial_init(void){

    struct serial_struct serial_req;
    int baud_base;

    /* Determine baud base */
    unsigned long cpc0_cr0 = mfdcr(DCRN_CPC0_CR0);

    if (cpc0_cr0 & 0x00400000){
        /* External UART0 clock (eval board uses 6*1.8432 MHz clock) */
        baud_base = (6 * 1843200) / 16;
    }
    else {
        /* Internal UART0 clock */
       int uart_div = ((cpc0_cr0 & 0x001f0000) >> 16) + 1;
        baud_base = (XXXXXX_clocks.plb * 1000000) / uart_div / 16;
    }

    /* Setup ioremapped serial port access */
    memset(&serial_req, 0, sizeof(serial_req));
    serial_req.line = 0;
    serial_req.baud_base = baud_base;
    serial_req.port = 0;
    serial_req.irq = UART0_INT;
    serial_req.flags = ASYNC_BOOT_AUTOCONF | ASYNC_SKIP_TEST;
    serial_req.io_type = SERIAL_IO_MEM;
    serial_req.iomem_base = ioremap64(PPC440GP_UART0_ADDR, 8);
    serial_req.iomem_reg_shift = 0;

    if (early_serial_setup(&serial_req) != 0) {
        printk(KERN_ALERT"Early serial init of port 0 failed\n");
    }
}

One comment, XXXXXX_clocks - structure that holds different clocks in MHz.
For example, XXXXXX_clocks.plb is equal to 133.

Usually, this value can be hardcoded, but I find this way more convenient,
especially when running the same image on different boards with different
clock setup.

Regards,

 Eugene Surovegin <mailto:ebs@innocent.com>


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