The RK3036 has only 8KB of RAM available for SPL. At present it uses its own debug UART code.
By allowing the ns16550 driver to provide a debug UART without providing a full serial driver, we can enable a UART with a very small overhead. This requires addition Kconfig options. The debug UART supports printhex8(), printascii() and a few other functions.
The root driver and uclass are pulled in by this series, but their size is very small. It would possible to drop these by disabling CONFIG_DM_SERIAL. However the ns16550 driver makes this hard, due to it supporting operation without driver model, and operating differently in this case.
Simon Glass (3): dm: serial: Allow the UART driver to be dropped from the image dm: ns16550: Allow the driver to be omitted if requested rockchip: Use the debug UART on rk3036
arch/arm/mach-rockchip/Makefile | 1 - arch/arm/mach-rockchip/rk3036-board-spl.c | 9 ++++- arch/arm/mach-rockchip/rk_early_print.c | 63 ------------------------------- configs/evb-rk3036_defconfig | 6 +++ drivers/serial/Kconfig | 20 ++++++++++ drivers/serial/ns16550.c | 2 + drivers/serial/serial-uclass.c | 2 + include/configs/rk3036_common.h | 2 + 8 files changed, 40 insertions(+), 65 deletions(-) delete mode 100644 arch/arm/mach-rockchip/rk_early_print.c