[U-Boot] [PATCH 1/4 v5] watchdog: Implement generic watchdog_reset() version

[Bin Meng]

Hi Stefan,

On Thu, Aug 15, 2019 at 2:07 PM Stefan Roese <sr at denx.de> wrote:
>
> Hi Simon,
>
> On 14.08.19 21:35, Simon Glass wrote:
> > Hi,
> >
> > On Wed, 14 Aug 2019 at 00:22, Stefan Roese <sr at denx.de> wrote:
> >>
> >> Hi Simon,
> >>
> >> (added Simon Glass and Bin to Cc)
> >>
> >> On 13.08.19 22:16, Simon Goldschmidt wrote:
> >>> Am 25.04.2019 um 09:17 schrieb Stefan Roese:
> >>>> 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>
> >>>
> >>> <snip>
> >>>
> >>>> --- a/include/asm-generic/global_data.h
> >>>> +++ b/include/asm-generic/global_data.h
> >>>> @@ -133,6 +133,9 @@ typedef struct global_data {
> >>>>       struct spl_handoff *spl_handoff;
> >>>>     # endif
> >>>>     #endif
> >>>> +#if defined(CONFIG_WDT)
> >>>> +    struct udevice *watchdog_dev;
> >>>> +#endif
> >>>>     } gd_t;
> >>>>     #endif
> >>>>
> >>>> @@ -161,5 +164,6 @@ typedef struct global_data {
> >>>>     #define GD_FLG_ENV_DEFAULT        0x02000 /* Default variable flag           */
> >>>>     #define GD_FLG_SPL_EARLY_INIT     0x04000 /* Early SPL init is done          */
> >>>>     #define GD_FLG_LOG_READY  0x08000 /* Log system is ready for use     */
> >>>> +#define GD_FLG_WDT_READY    0x10000 /* Watchdog is ready for use       */
> >>>
> >>> Sorry to warm up a thread that is more than 4 months old, but I just
> >>> stumbled accross this line when searching for space in 'gd':
> >>>
> >>> The comment some lines above in global_data.h clearly states that the
> >>> top 16 bits of flags are reserved for arch-specific flags, and your
> >>> patch here uses the lowest of these 16 arch-specific flags for generic code.
> >>
> >> I totally missed this comment.
> >>
> >>> Is this a problem? Does any arch code use the upper 16 bits? I would
> >>> have thought you'd at least need to adjust the comment to reflect your
> >>> new usage...
> >>
> >> As stated above, I did not check about any other (arch-specific)
> >> GD_FLG_ definitions outside of this file.
> >>
> >>> The reason I ask is that I'd need a place to put some (~5?)
> >>> 'is_initialized' bits for some code running in SPL in the 'board_init_f'
> >>> code where BSS shouldn't be used. gd->flags would be ideal for that, but
> >>> I'm hesistant to dive in further into the 'arch-specific' upper 16 bits...
> >>
> >> And you should be. A quick grep shows that we already have a problem with
> >> my patch touching the upper bits:
> >>
> >> $ git grep "define GD_FLG_"
> >> arch/x86/include/asm/global_data.h:#define GD_FLG_COLD_BOOT     0x10000 /* Cold Boot */
> >> arch/x86/include/asm/global_data.h:#define GD_FLG_WARM_BOOT     0x20000 /* Warm Boot */
> >>
> >> This should definitely be fixed. I see 3 options right now:
> >>
> >> a) Reserve only the upper 8 bits for arch-specific stuff
> >> b) Use a new variable (gd->flags_arch ?) for this arch
> >> c) Remove the arch-specific GD_FLG's completely
> >>
> >> I can't tell if c) is doable - Bin and / or Simon Glass might know,
> >> if the x86 GD_FLG_foo_BOOT are really needed in gd->flags. I see that
> >> both are assigned in the .S files, but only GD_FLG_COLD_BOOT is
> >> referenced later on:
> >
> > Probably we can drop warm boot.
>
> Bin, do you think so as well?
>

I believe we can drop these 2 flags completely. Currently usage of
warm/cold boot flags is only limited to coreboot codes.

arch/x86/cpu/coreboot/coreboot.c::last_stage_init()

        if (gd->flags & GD_FLG_COLD_BOOT)
                timestamp_add_to_bootstage();

timestamp_add_to_bootstage() will never be called for coreboot.

> >>
> >> arch/x86/cpu/coreboot/coreboot.c:       if (gd->flags & GD_FLG_COLD_BOOT)
> >>
> >> If c) is not an option, then I would prefer to implement b). Here
> >> we could also only add this new "flags_arch" variable for arch's
> >> that implement such flags (e.g. x86 right now). I could work on such
> >> a patch, if we agree on this solution.
> >>
> >> Any comments / suggestions?
> >
> > I'm not keen on arch-specific flags here. They should be in
> > gd->arch... if needed. global_data is current used by generic code.
> >
> > So maybe move the x86 flag to the generic header?
>
> Yes, I also think that those flags should not be sprinkled in different
> headers but collected in the generic header. I'll prepare a patch to
> move the x86 flags and remove the comment about the upper 16 bits
> usage. We can remove the x86 warm boot flag later, if this isn't
> used at all.
>

Regards,
Bin