[U-Boot] [PATCH PATCH v1] watchdog: Fix Watchdog Reset while in U-Boot Prompt

Simon Glass
2016-08-01T01:01:35Z

Hi,

On 13 July 2016 at 04:56, Andreas J. Reichel
<Andreas.Reichel@tngtech.com> wrote:
> Hardware: CM-FX6 Module from Compulab
>
> This patch fixes unwanted watchdog resets while the user enters
> a command at the U-Boot prompt.
>
> As found on the CM-FX6 board from Compulab, when having enabled the
> watchdog, a missing WATCHDOG_RESET call in common/console.c causes
> this and alike boards to reset when the watchdog's timeout has
> elapsed while waiting at the U-Boot prompt.
>
> Despite the user could press several keys within the watchdog
> timeout limit, the while loop in cli_readline.c, line 261, does only
> call WATCHDOG_RESET if first == 1, which gets set to 0 in the 1st
> loop iteration. This leads to a watchdog timeout no matter if the
> user presses keys or not.
>
> Although, this affects other boards as well as it touches
> common/console.c, the macro WATCHDOG_RESET expands to {} if watchdog
> support isn't configured. Hence, there's no harm caused and no need to
> surround it by #ifdef in this case.
>
> * Symptom:
> U-Boot resets after watchdog times out when in commandline prompt
> and watchdog is enabled.
>
> * Reasoning:
> When U-Boot shows the commandline prompt, the following function
> call stack is executed while waiting for a keypress:
>
> common/main.c:
> main_loop => common/cli.c: cli_loop() =>
> common/cli_hush.c:
> parse_file_outer => parse_stream_outer =>
> parse_stream => b_getch(i) =>
> i->get(i) => file_get =>
> get_user_input => cmdedit_read_input =>
> uboot_cli_readline =>
> common/cli_readline.c:
> cli_readline => cli_readline_into_buffer =>
> cread_line => getcmd_getch (== getc) =>
> common/console.c:
> fgetc => console_tstc
>
> common/console.c:
> (with CONFIG_CONSOLE_MUX is set)
>
> - in console_tstc line 181:
> If dev->tstc(dev) returns 0, the global tstcdev variable doesn't get
> set. This is the case if no character is in the serial buffer.
>
> - in fgetc(int file), line 297:
> Program flow keeps looping because tstcdev does not get set.
> Therefore WATCHDOG_RESET is not called, as mx_serial_tstc from
> drivers/serial/serial_mxc.c does not call it.
>
> * Solution:
> Add WATCHDOG_RESET into the loop of console_tstc.
>
> Note: Macro expands to {} if not configured, so no #ifdef is needed.
>
> * Comment:
>
> Signed-off-by: Christian Storm <christian.storm@tngtech.com>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> Signed-off-by: Andreas J. Reichel <Andreas.Reichel@tngtech.com>

Thanks for the detailed info.

Would it be better to put this in _serial_tstc()?

> ---
>
> common/console.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/common/console.c b/common/console.c
> index 12293f3..054b6cd 100644
> --- a/common/console.c
> +++ b/common/console.c
> @@ -16,6 +16,7 @@
> #include <stdio_dev.h>
> #include <exports.h>
> #include <environment.h>
> +#include <watchdog.h>
>
> DECLARE_GLOBAL_DATA_PTR;
>
> @@ -294,6 +295,7 @@ int fgetc(int file)
> * Effectively poll for input wherever it may be available.
> */
> for (;;) {
> + WATCHDOG_RESET();
> /*
> * Upper layer may have already called tstc() so
> * check for that first.
> --
> 2.8.2
>

Regards,
Simon