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

[Tom Rini <trini@konsulko.com>]

On Wed, Jul 13, 2016 at 12:56:51PM +0200, Andreas J. Reichel 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>
> Acked-by: Simon Glass <sjg@chromium.org>

Applied to u-boot/master, thanks!

-- 
Tom
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