But even if earlycon works, you need to enable DEBUG_LL & respective DEBUG_UART & you can pass earlyprintk=1 as a CMDLINE argument
Regards, Jagan On Tue, Nov 1, 2011 at 4:14 PM, Sam King <[email protected]> wrote: > 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 <[email protected]> wrote: > > For early boot logs, did you enabled required configs???? > > > > Regards, > > Jagan. > > > > > > > > > > > > > > > > On Mon, Oct 31, 2011 at 8:43 PM, Sam King <[email protected]> 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: [email protected] > > > website:http://groups.google.com/group/android-kernel > > -- > unsubscribe: [email protected] > website: http://groups.google.com/group/android-kernel > -- unsubscribe: [email protected] website: http://groups.google.com/group/android-kernel
