This patchset adds RISC-V SBI earlycon and removes RISC-V EARLY_PRINTK. We should use earlycon over existing EARLY_PRINTK for SBI console because: 1. It's a more generic way of implementing early console for debugging 2. Current RISC-V EARLY_PRINTK is a compile-time option whereas earlycon is enabled at run-time via kernel parameters. 3. To use earlycon with SBI, we have to pass "earlycon=sbi" in kernel parameters. If earlycon kernel parameter is not provided then kernel boots much faster which is very useful in real-world RISC-V deployments.
The patchset is tested on QEMU virt machine. It is based on Linux-4.20-rc5 and can be found at riscv_earlycon_v1 branch of: https://github.com/avpatel/linux.git Anup Patel (3): tty/serial: Add RISC-V SBI earlycon support RISC-V: defconfig: Enable RISC-V SBI earlycon support RISC-V: Remove EARLY_PRINTK support arch/riscv/Kconfig.debug | 2 -- arch/riscv/configs/defconfig | 1 + arch/riscv/kernel/setup.c | 28 ------------------------- drivers/tty/serial/Kconfig | 12 +++++++++++ drivers/tty/serial/Makefile | 1 + drivers/tty/serial/earlycon-riscv-sbi.c | 28 +++++++++++++++++++++++++ 6 files changed, 42 insertions(+), 30 deletions(-) create mode 100644 drivers/tty/serial/earlycon-riscv-sbi.c -- 2.17.1
