[PATCH 0/3] RISC-V SBI earlycon

Anup Patel
2018-12-04T14:10:50Z

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

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2.17.1