Missing frame buffer parameter passed by U-Boot to Kernel

[herry13]

Although U-Boot has a nice, correct screen size console, but the kernel always switches the display to (default) colour frame buffer device 100x30 lines, as shown in following log:

Console: switching to colour frame buffer device 100x30

Meanwhile Raspbian, that uses RaspberryPi Foundation's boot loader, switches the display to a correct frame buffer configuration by giving these parameters to the kernel:

bcm2708_fb.fbwidth=1920 bcm2708_fb.fbheight=1200 bcm2708_fb.fbswap=1

Maybe related, it also passes video card memory parameters:

vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000

The solution is that U-Boot should pass correct frame buffer parameters to the kernel. An example of obtaining the screen size can be found in function lcd_dt_simplefb_configure_node [2] called by ft_board_setup [1]. The latter can be modified to expose the screen width and height as environment variables fbwidth and fbheight respectively. These variables is then added into bootargs

An alternative, more complex solution would be reading the frame buffer parameters given by start.elf and expose them as above environment variables.

[1] https://github.com/u-boot/u-boot/blob/1811a928c6c7604d6d05a84b4d552a7c31b4994e/board/raspberrypi/rpi/rpi.c#L446
[2] https://github.com/u-boot/u-boot/blob/05b8dc5cd30a6d6cdfb29c9e718198692e12b4bf/common/lcd_simplefb.c#L19