[U-Boot-Users] serial does not work

my card use powerpc 440gx, i use u-boot OCOTEA board. when i arrive the prompt "=>", i can input no char. at last i find that cpu always loops in the function of serial_getc() whatever i press any button. i have no error. cpu-->ppc4xx-->serial.c status = in8 (ACTING_UART0_BASE + UART_LSR); if ((status & asyncLSRDataReady1) != 0x0) { break; } the result of (status & asyncLSRDataReady1) always is zero. i do not know why.