[LinuxBIOS] About CS5536 UART2 and USB boot !

Gard xu gardxu at gmail.com
Thu Jun 14 12:20:11 CEST 2007

Hi all :
        My target  is Geode LX800 + CS5536., Linuxbios rev2550 base on
mainboard dbe61. It can boot linux(2.6.20) with IDE and work well.But now
there are two questions trouble me some days.
       1. MY target use CS5536's UART1 as COM1,It can work normally.When I
try to use the CS5536's UART2  as a general serial COM2 but not the
DDC(display data channel), It seem badly. I has set  the registers about
UART2 refer to CS5536 datashee in linuxbios( *1*. set bit 20:22 of msr
0x51400014  to  6 ;   *2*. set msr 0x5140003e bit 1 and bit 4 as 1. * 3*.
set GPIO3(RX) Input Enable and Input AUX1 select  = 1 , set GPIO4(TX) output
enable and output AUX1 select = 1.). After booting the OS, I read back the
register above through my driver found that all  preset value is zero,UART2
can't work. I try to set that registers again in my driver,this time it read
back value is right, but UART2 still can't work.
                          /dev/ttyS1, Line 1, UART: unknown, Port: 0x02f8,
IRQ: 3
                          Baud_base: 115200, close_delay: 50, divisor: 0
                          closing_wait: 3000
                          Flags: spd_normal skip_test auto_irq
why? maybe kernel use UART2's GPIO pin to act as DDC use,so it change my
preset  when linux is booting?  or my configuration about UART2 is not
correct ?

       2. I has try to use ethboot5.2.6 to boot my system  from USB
Disk,when with the IDE on mainboard, It can boot well. but if without IDE,It
will hang up at " checking if this processor honours the WP bit even in
supervisor mode...ok " after starting the kernel. it seem strange.when I
debug it in kernel, I found it cycle in calibrate.c---> function static
unsigned long __devinit calibrate_delay_direct(void) all along. because the
jiffies is not increase,so it cycle there. Here my question is: *1*.what
diffrent about without IDE or not(PCI scanning  will change some setup
about linuxbios normal when without IDE? ),.why jiffies can't increase when
withou IDE? it seems  PIT 8254 interrupt problem lead it, what should I do
to modify some setup in linuxbios  to avoid this problem?

       Help me please :)  thanks!!!
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