Hello,
I am having trouble getting information out of my tegra2 (ventana)
system early in the boot sequence, which is making debugging some
early boot code I am working on nearly impossible. My code runs right
after the bootloader well before the MMU has been enabled. I tried
writing pixel valued directly to both of the video memory regions for
my platform, but nothing happend. Since fastboot prints some simple
messages to the screen I am assuming this is possible, I just can't
figure out how.
I also tried enabling the early boot 8250 driver and I tried writing
directly to the serial port myself using this code, any help is
appreciated:
#define FCR (2<<2)
#define IER (1<<2)
#define DLL 0
#define DLH (1<<2)
#define LCR (3<<2)
#define MCR (4<<2)
#define TX 0
#define LCR_DLAB 0x80
.global _reset
_reset:
/* physical serial port location, uses 8250 interface on
ventana board */
ldr r0, =0x70006300
/* 8n1 */
mov r1, #0x3
strb r1, [r0, #LCR]
/* interrupts off */
mov r1, #0
strb r1, [r0, #IER]
/* no fifo */
mov r1, #0
strb r1, [r0, #FCR]
/* 115200 baud rate, usbclk is 216000000 for ventana divisor
= 0x75 */
ldrb r1, [r0, #LCR]
orr r1, r1, #LCR_DLAB
strb r1, [r0, #LCR]
mov r1, #0x75
strb r1, [r0, #DLL]
mov r1, #0x0
strb r1, [r0, #DLH]
mov r1, #3
strb r1, [r0, #LCR]
/* Send an 'A' */
mov r1, #0x41
strb r1, [r0, #TX]
--
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