[PATCH 0/6] Early console buffer for OpenSBI

[Anup Patel]

On Mon, Jul 8, 2024 at 10:19 PM Xiang W <wxjstz at 126.com> wrote:
>
> 在 2024-07-05星期五的 12:44 +0530，Anup Patel写道：
> > This series tries to improve OpenSBI debugging by:
> > 1) Registering console device via platform early_init()
> > 2) Introducing early console buffer
> >
> > These patches can also be found in the console_early_probe_v1
> > branch at: https://github.com/avpatel/opensbi.git
> >
> > Anup Patel (6):
> >   platform: Setup serial console device in early_init()
> >   lib: sbi: Remove sbi_console_init() and console_init() platform
> >     callback
> >   lib: sbi: Optimize fifo enqueue/dequeue for basic data types
> >   lib: sbi: Allow forceful queueing of data in sbi_fifo_enqueue()
> >   include: sbi: Add macros to create FIFO as local or global variable
> >   lib: sbi: Introduce an early console buffer for caching early prints
> >
> Hi, Anup
>
> Before the console is initialized, sbi_printf is only called if an error
> occurs, and an error usually causes the program to enter sbi_hart_hang,
> resulting in no output. This makes adding an early console buffer less
> useful. The program will crash anyway, and we don't need to care about
> the order of function calls, we should just output some useful information
> as much as possible.

If the program crashes before early_init() then users can use HW debugger
to dump the contents of the early console. This practice has been followed
in other open source projects as well.

There is always a small boot time window across system level software
(such as bootloader, firmware, OS kernels and hypervisors) where if a
failure occurs in this window then it will result in no prints. The goal
should be to minimize this boot time window and make it robust
without working-around or hacking driver dependency.

Currently, the sbi_domain_init() must be completed before the serial
drivers are probed. You can certainly to do a ugly work-around to split
the serial driver init into two parts but what if the serial drivers also use
heap in the future. There is no end to such work-arounds.

Directly initializing the console from sbi_hart_hang() is
NOT A MAINTAINABLE approach.

Regards,
Anup

>
> Regards,
> Xiang W
> >  include/sbi/sbi_console.h          |  2 -
> >  include/sbi/sbi_fifo.h             | 14 +++++-
> >  include/sbi/sbi_platform.h         | 17 -------
> >  lib/sbi/Kconfig                    |  6 ++-
> >  lib/sbi/sbi_console.c              | 36 ++++++++++-----
> >  lib/sbi/sbi_fifo.c                 | 72 +++++++++++++++++++++++++-----
> >  lib/sbi/sbi_init.c                 |  4 --
> >  lib/sbi/sbi_sse.c                  |  2 +-
> >  lib/sbi/sbi_tlb.c                  |  3 +-
> >  platform/fpga/ariane/platform.c    | 26 ++++-------
> >  platform/fpga/openpiton/platform.c | 20 ++-------
> >  platform/generic/platform.c        | 21 ++++-----
> >  platform/kendryte/k210/platform.c  | 18 +++-----
> >  platform/nuclei/ux600/platform.c   | 18 +++-----
> >  platform/template/platform.c       | 18 +++-----
> >  15 files changed, 151 insertions(+), 126 deletions(-)
> >
> > --
> > 2.34.1
> >
> >
>