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

[Tom Rini <trini@konsulko.com>]

On Mon, Sep 19, 2016 at 01:59:44PM +0200, Andreas Reichel wrote:
> Hi Tom,
> 
> is my patch going to be applied or is the problem resolved
> otherwhise?

Sorry, lost in my patchwork queue.  I'll pick this up soon now.

> 
> 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@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@tngtech.com>
> > > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > > Signed-off-by: Andreas J. Reichel <Andreas.Reichel@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@chromium.org>
> > 
> > >
> > > --
> > > 2.8.2
> > >
> 
> -- 
> Andreas Reichel 
> Dipl.-Phys. (Univ.) 
> Software Consultant
> 
> Andreas.Reichel at tngtech.com 
> +49-174-3180074
> 
> TNG Technology Consulting GmbH, Betastr. 13a, 85774 Unterf?hring
> Gesch?ftsf?hrer: Henrik Klagges, Christoph Stock, Dr. Robert Dahlke
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-- 
Tom
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