Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

On Thu 18 Apr 2019 at 18:04, Atish Patra [off-list ref] wrote:

On 4/18/19 4:22 PM, Kevin Hilman wrote:

quoted

Hi Paul,

Paul Walmsley [off-list ref] writes:

quoted

This series adds a serial driver, with console support, for the
UART IP block present on the SiFive FU540 SoC.  The programming
model is straightforward, but unique.

Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
open-source FSBL (with appropriate patches to the DT data).

This fifth version fixes a bug in the set_termios handler,
found by Andreas Schwab [off-list ref].

The patches in this series can also be found, with the PRCI patches,
DT patches, and DT prerequisite patch, at:

https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4

I tried this branch, and it doesn't boot on my unleashed board.

Here's the boot log when I pass the DT built from your branch via
u-boot: https://termbin.com/rfp3.

Unfortunately, that won't work. The current DT modifications by OpenSBI.

1. Change hart status to "masked" from "okay".
2. M-mode interrupt masking in PLIC node.
3. Add a chosen node for serial access in U-Boot.

You can ignore 3 for your use case. However, if you pass a dtb built from source
code, that will have hart0 enabled and M-mode interrupts enabled in DT.

Atish,
I'm trying to get the kernel boot with the current linux kernel DT from
Paul's patch series [0].

Could you point me to some documentation on 2. ?
Or do you know of a way to disable M-mode interrupts from U-boot ?

[0]: https://lore.kernel.org/patchwork/project/lkml/list/?series=390077

Thanks,
Loys

Not sure if we should do these DT modifications in U-Boot as well.