[PATCH 6/6] lib: sbi: Introduce an early console buffer for caching early prints

[Himanshu Chauhan]

On Fri, Jul 5, 2024 at 12:45 PM Anup Patel <apatel at ventanamicro.com> wrote:
>
> The console device is registered by platform only in early_init()
> callback so any prints before this point will be lost. Introduce an
> early console buffer for caching prints before platform early_init().
>
> For crashes before platform early_init(), users can simply dump the
> contents of the console_early_buffer[] string using a debugger. The
> relative address of the console_early_buffer[] string can be found
> using following two commands:
>
> CONSOLE_EARLY_FIFO_ADDR=`${CROSS_COMPILE}objdump -D \
> build/platform/generic/firmware/fw_dynamic.elf | \
> grep "<console_early_fifo>:" | awk '{print $1}'`
>
> ${CROSS_COMPILE}objdump -R build/platform/generic/firmware/fw_dynamic.elf | \
> grep $CONSOLE_EARLY_FIFO_ADDR | awk '{print $3}'
>
> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> ---
>  lib/sbi/Kconfig       |  6 +++++-
>  lib/sbi/sbi_console.c | 27 +++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/lib/sbi/Kconfig b/lib/sbi/Kconfig
> index 6cf54ce..bd8ba2b 100644
> --- a/lib/sbi/Kconfig
> +++ b/lib/sbi/Kconfig
> @@ -1,6 +1,10 @@
>  # SPDX-License-Identifier: BSD-2-Clause
>
> -menu "SBI Extension Support"
> +menu "Generic SBI Support"
> +
> +config CONSOLE_EARLY_BUFFER_SIZE
> +       int "Early console buffer size (bytes)"
> +       default 256
>
>  config SBI_ECALL_TIME
>         bool "Timer extension"
> diff --git a/lib/sbi/sbi_console.c b/lib/sbi/sbi_console.c
> index 194529d..d760885 100644
> --- a/lib/sbi/sbi_console.c
> +++ b/lib/sbi/sbi_console.c
> @@ -9,6 +9,7 @@
>
>  #include <sbi/riscv_locks.h>
>  #include <sbi/sbi_console.h>
> +#include <sbi/sbi_fifo.h>
>  #include <sbi/sbi_hart.h>
>  #include <sbi/sbi_platform.h>
>  #include <sbi/sbi_scratch.h>
> @@ -21,6 +22,15 @@ static char console_tbuf[CONSOLE_TBUF_MAX];
>  static u32 console_tbuf_len;
>  static spinlock_t console_out_lock            = SPIN_LOCK_INITIALIZER;
>
> +#ifdef CONFIG_CONSOLE_EARLY_BUFFER_SIZE
> +#define CONSOLE_EARLY_BUFFER_SIZE      CONFIG_CONSOLE_EARLY_BUFFER_SIZE
> +#else
> +#define CONSOLE_EARLY_BUFFER_SIZE      256
> +#endif
> +static char console_early_buffer[CONSOLE_EARLY_BUFFER_SIZE] = { 0 };
> +static SBI_FIFO_DEFINE(console_early_fifo, console_early_buffer, \
> +                      CONSOLE_EARLY_BUFFER_SIZE, sizeof(char));
> +
>  bool sbi_isprintable(char c)
>  {
>         if (((31 < c) && (c < 127)) || (c == '\f') || (c == '\r') ||
> @@ -39,6 +49,7 @@ int sbi_getc(void)
>
>  static unsigned long nputs(const char *str, unsigned long len)
>  {
> +       char ch;
>         unsigned long i;
>
>         if (console_dev) {
> @@ -51,6 +62,11 @@ static unsigned long nputs(const char *str, unsigned long len)
>                                 console_dev->console_putc(str[i]);
>                         }
>                 }
> +       } else {
> +               for (i = 0; i < len; i++) {
> +                       ch = str[i];
> +                       sbi_fifo_enqueue(&console_early_fifo, &ch, true);
> +               }
>         }
>         return len;
>  }
> @@ -472,8 +488,19 @@ const struct sbi_console_device *sbi_console_get_device(void)
>
>  void sbi_console_set_device(const struct sbi_console_device *dev)
>  {
> +       char ch;
> +       bool flush_early_fifo = false;
> +
>         if (!dev)
>                 return;
>
> +       if (!console_dev)
> +               flush_early_fifo = true;
> +
>         console_dev = dev;
> +
> +       if (flush_early_fifo) {
> +               while (!sbi_fifo_dequeue(&console_early_fifo, &ch))
> +                       sbi_putc(ch);
> +       }
>  }
> --
> 2.34.1
>

LGTM

Reviewed-By: Himanshu Chauhan <hchauhan at ventanamicro.com>

>
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