# Question about SMC serial port on MPC8270 in u-boot

- From: FCG WANG Baohua \<hidden\>
- Date: 2005-08-31 00:52:40 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2005/08/9400746

```text
Dear All:
 When i port the u-boot 1.1.3 on my MPC8270 board, the serial port has the following question:
  1. the Dual port ram cannot be revised manually, but can be revised by the u-boot code. What's the problem?
   2. the serial_putc() in serial_smc.c is loop forever on  "while (tbdf->cbd_sc & BD_SC_READY);". How to slove the bug?
   3. the speed.c calc the wrong cpm, cpu, brg_clk, I had hard coded the right   cpm, cpu, brg_clk values. But the "m8260_cpm_setbrg()" is still wrong? Why?
       the registers are all right.
   4. Can you tell me the ALL items about the SMC1  UART output? I had checked almost all the concerned SMC registers, IO ports,
        data structures, they all seems right, but the UART cannot work. How could I find the problem? 
   thanks a lot ! 


```