[U-Boot] [PATCH v2] watchdog: Fix Watchdog Reset while in U-Boot Prompt

[Andreas Reichel]

Hi Tom,

is my patch going to be applied or is the problem resolved
otherwhise?

Kind regards
    Andreas

On Mo, Sep 05, 2016 at 07:04:53 -0600, Simon Glass wrote:
> +Tom, in case this should go into the release.
> 
> On 1 August 2016 at 05:49, Andreas J. Reichel
> <Andreas.Reichel at tngtech.com> wrote:
> > 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 _serial_tstc() in
> > (/drivers/serial/serial-uclass.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.
> >
> > The problem is solved with a call to WATCHDOG_RESET in _serial_tstc,
> > defined in drivers/serial/serial-uclass.c.
> >
> > Since the macro WATCHDOG_RESET expands to {} if watchdog support
> > isn't configured, there's 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)   =>
> >    commonn/console.c:
> >                     fgetc              => console_tstc
> >
> >    - 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.
> >
> >    - Initialization calls drv_system_init in stdio.c, which sets
> >    dev.tstc = stdio_serial_tstc. Thus, dev->tstc(dev) calls serial_tstc()
> >    which in turn calls _serial_tstc().
> >
> >    Hence, _serial_tstc() needs to call WATCHDOG_RESET() to periodically
> >    reset the watchdog while cli_readline waits for user input.
> >
> > Signed-off-by: Christian Storm <christian.storm at tngtech.com>
> > Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
> > Signed-off-by: Andreas J. Reichel <Andreas.Reichel at tngtech.com>
> > ---
> >
> > Changes in v2:
> >  - Move WATCHDOG_RESET() call from common/console.c to
> >    drivers/serial/serial-uclass.c.
> >
> >  drivers/serial/serial-uclass.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c
> > index 0ce5c44..72cf808 100644
> > --- a/drivers/serial/serial-uclass.c
> > +++ b/drivers/serial/serial-uclass.c
> > @@ -155,6 +155,7 @@ static int _serial_tstc(struct udevice *dev)
> >  {
> >         struct dm_serial_ops *ops = serial_get_ops(dev);
> >
> > +       WATCHDOG_RESET();
> >         if (ops->pending)
> >                 return ops->pending(dev, true);
> 
> Great explanation, thank you.
> 
> Acked-by: Simon Glass <sjg at chromium.org>
> 
> >
> > --
> > 2.8.2
> >

-- 
Andreas Reichel 
Dipl.-Phys. (Univ.) 
Software Consultant

Andreas.Reichel at tngtech.com 
+49-174-3180074

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