[0/3] RISC-V SBI earlycon

Message

Anup Patel Dec. 4, 2018, 1:55 p.m. UTC

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

Comments

Palmer Dabbelt Dec. 7, 2018, 6:30 p.m. UTC | #1

On Tue, 04 Dec 2018 05:55:04 PST (-0800), [e-mail] wrote:
> 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

I'm adding these to my for-next.

Thanks!

Andreas Schwab March 25, 2019, 4:23 p.m. UTC | #2

On Dez 04 2018, Anup Patel <[e-mail]> wrote:

> 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.

Why doesn't this earlycon disable itself when the real console kicks in?

Andreas.