I did try using the earlycon kernel command line argument, but it did not work.
It turns out that the version of fastboot that I am using uses a non- standard (nvidia specific) atag value to pass the bootloader framebuffer to the kernel. With this I can write to the screen. Although I can write to the screen now I am curious as to why earlycon did not work if anyone knows how to do this properly. --Sam On Nov 1, 2:14 am, jagan <402ja...@gmail.com> wrote: > For early boot logs, did you enabled required configs???? > > Regards, > Jagan. > > > > > > > > On Mon, Oct 31, 2011 at 8:43 PM, Sam King <kin...@gmail.com> wrote: > > 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] > > > -- > > unsubscribe: android-kernel+unsubscr...@googlegroups.com > > website:http://groups.google.com/group/android-kernel -- unsubscribe: android-kernel+unsubscr...@googlegroups.com website: http://groups.google.com/group/android-kernel
