[U-Boot] [PATCH 1/2 v2] watchdog: Implement generic watchdog_reset() version

[Stefan Roese]

On 09.04.19 16:27, Michal Simek wrote:
> On 09. 04. 19 16:22, Stefan Roese wrote:
>> On 09.04.19 12:45, Michal Simek wrote:
>>> On 08. 04. 19 11:28, Stefan Roese wrote:
>>>> This patch tries to implement a generic watchdog_reset() function that
>>>> can be used by all boards that want to service the watchdog device in
>>>> U-Boot. This watchdog servicing is enabled via CONFIG_WATCHDOG.
>>>>
>>>> Without this approach, new boards or platforms needed to implement a
>>>> board specific version of this functionality, mostly copy'ing the same
>>>> code over and over again into their board or platforms code base.
>>>>
>>>> With this new generic function, the scattered other functions are now
>>>> removed to be replaced by the generic one. The new version also enables
>>>> the configuration of the watchdog timeout via the DT "timeout-sec"
>>>> property (if enabled via CONFIG_OF_CONTROL).
>>>>
>>>> This patch also adds a new flag to the GD flags, to flag that the
>>>> watchdog is ready to use and adds the pointer to the watchdog device
>>>> to the GD. This enables us to remove the global "watchdog_dev"
>>>> variable, which was prone to cause problems because of its potentially
>>>> very early use in watchdog_reset(), even before the BSS is cleared.
>>>>
>>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>>> Cc: Heiko Schocher <hs at denx.de>
>>>> Cc: Tom Rini <trini at konsulko.com>
>>>> Cc: Michal Simek <michal.simek at xilinx.com>
>>>> Cc: "Marek Behún" <marek.behun at nic.cz>
>>>> Cc: Daniel Schwierzeck <daniel.schwierzeck at gmail.com>
>>>> ---
>>>> This patch depends on the following patches:
>>>>
>>>> [1] watchdog: Move watchdog_dev to data section (BSS may not be cleared)
>>>> https://patchwork.ozlabs.org/patch/1075500/
>>>>
>>>> [2] watchdog: Handle SPL build with watchdog disabled
>>>> https://patchwork.ozlabs.org/patch/1074098/
>>>>
>>>> I would like to see [1] applied in this release, since its a real fix on
>>>> some of the platforms with minimal chances of breakage.
>>>>
>>>> This patch now is a bigger rework and is intended for the next merge
>>>> window.
>>>>
>>>> Please note that I didn't remove the "timeout-sec" handling from the
>>>> driver already reading it from the DT (cdns & at91) in this patch.
>>>> The reason for this is, that in the cdns case, the removal also brings
>>>> a functional change, which I wanted to do in a separate patch. And
>>>> in the at91 case its because there are updates to this driver already
>>>> queued in the at91 next git branch which would most likely cause merge
>>>> conflict. I'll send a cleanup patch for this driver later after these
>>>> patches have been applied.
>>>>
>>>> Thanks,
>>>> Stefan
>>>>
>>>> v2:
>>>> - Rename watchdog_start() to initr_watchdog() and move it to board_r.c.
>>>>     This way its only called once, after the DM subsystem has bound all
>>>>     watchdog drivers. This enables the use of the currently implemented
>>>>     logic of using the correct watchdog in U-Boot (via alias etc).
>>>>
>>>>    arch/mips/mach-mt7620/cpu.c                   | 36 -----------------
>>>>    board/CZ.NIC/turris_mox/turris_mox.c          | 30 --------------
>>>>    board/CZ.NIC/turris_omnia/turris_omnia.c      | 35 ----------------
>>>>    .../microblaze-generic/microblaze-generic.c   | 40 -------------------
>>>>    board/xilinx/zynq/board.c                     | 39 ------------------
>>>>    board/xilinx/zynqmp/zynqmp.c                  | 39 ------------------
>>>>    common/board_r.c                              | 40 +++++++++++++++++++
>>>>    drivers/watchdog/wdt-uclass.c                 | 26 ++++++++++++
>>>>    include/asm-generic/global_data.h             |  4 ++
>>>>    9 files changed, 70 insertions(+), 219 deletions(-)
>>
>> <snip>
>>
>>>>    int board_early_init_r(void)
>>>>    {
>>>>        u32 val;
>>>> diff --git a/common/board_r.c b/common/board_r.c
>>>> index 472987d5d5..d80f16c3ed 100644
>>>> --- a/common/board_r.c
>>>> +++ b/common/board_r.c
>>>> @@ -48,6 +48,7 @@
>>>>    #include <linux/compiler.h>
>>>>    #include <linux/err.h>
>>>>    #include <efi_loader.h>
>>>> +#include <wdt.h>
>>>>      DECLARE_GLOBAL_DATA_PTR;
>>>>    @@ -621,6 +622,42 @@ static int initr_bedbug(void)
>>>>    }
>>>>    #endif
>>>>    +#if defined(CONFIG_WATCHDOG) && defined(CONFIG_WDT)
>>>
>>> This is not correct.
>>> Here should be just CONFIG_WDT.
>>>
>>> Because there are cases where you want just start watchdog in u-boot but
>>> never service it by u-boot.
>>
>> AFAIK, this would change the current behavior. Currently, only when
>> CONFIG_WATCHDOG is enabled the watchdog driver is started automatically
>> in U-Boot (and serviced). If I make the change you suggest above, all
>> boards defining CONFIG_WDT (DM watchdog support) will automatically
>> enable the watchdog. This might make sense, but AFAICT this changes
>> the current behavior.
> 
> The question is what default is. Because when I was adding support for
> Zynq/ZynqMP/Microblaze this logic is used there.
> I think that WDT should be there and if you think there are boards which
> want to have both we can cover that by Kconfig.

As mentioned above, I agree that it makes sense to start the watchdog
automatically, if its enabled / selected via CONFIG_WDT. I suggest
that I move forward with your suggested change, but it would be fair
to Cc the maintainers of boards that have CONFIG_WDT set but
CONFIG_WATCHDOG unset. Do you (or anyone else) know of a tool / script
to detect such board configurations in U-Boot (one option set and
another unset)?

Thanks,
Stefan