Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

[Xingyu Chen]

Hi, Julius

On 2020/2/25 9:23, Julius Werner wrote:
>> The SMC function ID may be solved by the DTS, but the wdt indexs(Eg:
>> SMCWD_INFO) are also different
>> for each vendor. The imx_sc_wdt.c is also use the SMC to operate the
>> WDT, but the wdt indexs(Eg: IMX_SIP_TIMER_START_WDOG)
>> are different from ours. IMO, If the ATF can implement a common hal
>> interface and index for watchdog, then writing a
>> common smc wdt driver will be easier to compatible with all vendors.
> The MediaTek driver is still in flux (e.g. still being reviewed in
> Trusted Firmware here:
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405),
> we can still change it. So if we can now decide on making this a
> "standard" driver, we can change the MediaTek interface to match IMX
> and standardize on that. (There are existing Chromebooks shipped with
> a different interface, but we could handle those separately with
> downstream patches. I think having a unified interface that will
> prevent this problem in the future would be worth some extra
> complication right now.)
If the ATF provides a common watchdog hal interface and index, I am 
happy to match
the generic sec wdt driver. Compared to the current MTK wdt index [0], 
the following
indexes need to be supported for meson wdt [1].
- *_INIT.
- *_GETTIMEOUT.
- *_RESETNOW.  It is used to reset the system right now, similar to your 
SOFT RESET.

For another platform-specific parameter "SMC function ID", the generic 
sec wdt driver can get it from the dts, but if
the driver want to compatible with more vendors in the future, maybe we 
should consider Guenter's suggestion at [2]

[0]: https://patchwork.kernel.org/patch/11395579/
[1]: https://patchwork.kernel.org/patch/11331271/
[2]: 
https://lore.kernel.org/linux-watchdog/20200220155159.GB29658@roeck-us.net/T/#md00328548222965054cd19ec7dda074f8fc09fe2

Best Regards
> .

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Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

[Evan Benn]

Hi Xingyu,

I am trying to establish some clarity about what to do here.

The trusted firmware review has now been accepted
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405.

I could try to add your mentioned extra operation indexes to the ATF
watchdog, to try to establish a standard ATF smc watchdog interface.
Hypothetically then your linux driver could connect to any of the ATF
watchdogs, apart from the meson indirection layer.
I do not quite understand the meson layer to be honest, would we run
the meson layer on non-amlogic SOCs?

It looks feasible to strip the meson part from your driver so that it
works on more socs, please correct me if I am wrong.

Alternatively we could also add these extra operation indexes to this
linux driver. Unfortunately I would not have a way to test that.

Thanks

Evan

On Tue, Feb 25, 2020 at 6:43 PM Xingyu Chen <xingyu.chen@amlogic.com> wrote:
>
> Hi, Julius
>
> On 2020/2/25 9:23, Julius Werner wrote:
> >> The SMC function ID may be solved by the DTS, but the wdt indexs(Eg:
> >> SMCWD_INFO) are also different
> >> for each vendor. The imx_sc_wdt.c is also use the SMC to operate the
> >> WDT, but the wdt indexs(Eg: IMX_SIP_TIMER_START_WDOG)
> >> are different from ours. IMO, If the ATF can implement a common hal
> >> interface and index for watchdog, then writing a
> >> common smc wdt driver will be easier to compatible with all vendors.
> > The MediaTek driver is still in flux (e.g. still being reviewed in
> > Trusted Firmware here:
> > https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405),
> > we can still change it. So if we can now decide on making this a
> > "standard" driver, we can change the MediaTek interface to match IMX
> > and standardize on that. (There are existing Chromebooks shipped with
> > a different interface, but we could handle those separately with
> > downstream patches. I think having a unified interface that will
> > prevent this problem in the future would be worth some extra
> > complication right now.)
> If the ATF provides a common watchdog hal interface and index, I am
> happy to match
> the generic sec wdt driver. Compared to the current MTK wdt index [0],
> the following
> indexes need to be supported for meson wdt [1].
> - *_INIT.
> - *_GETTIMEOUT.
> - *_RESETNOW.  It is used to reset the system right now, similar to your
> SOFT RESET.
>
> For another platform-specific parameter "SMC function ID", the generic
> sec wdt driver can get it from the dts, but if
> the driver want to compatible with more vendors in the future, maybe we
> should consider Guenter's suggestion at [2]
>
> [0]: https://patchwork.kernel.org/patch/11395579/
> [1]: https://patchwork.kernel.org/patch/11331271/
> [2]:
> https://lore.kernel.org/linux-watchdog/20200220155159.GB29658@roeck-us.net/T/#md00328548222965054cd19ec7dda074f8fc09fe2
>
> Best Regards
> > .

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Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

[Julius Werner]

> - *_INIT and *GETTIMEOUT.      Although your driver does not need them, could you take them as options in your driver ?

The driver already has SMCWD_INFO which is used during probe to
retrieve the minimum and maximum timeout values supported by the
hardware at probe time. Maybe it would make sense to rename that to
INIT (which would still return those values, but can also do whatever
initialization needs to be done in TF)? GETTIMELEFT I agree we can
implement optionally, and other platforms would just return a
PSCI_RET_NOT_SUPPORTED for that.

> - *_RESETNOW.      It is used to reset the system right now, similar to your SOFT RESET. could you reserve an operation index in ATF ?

Just curious, why do you need this? Shouldn't you use the PSCI
standard SYSTEM_RESET SMC for that? (If you want to control exactly
how the platform is reset, you could also use SYSTEM_RESET2 with a
vendor-defined reset_type.)

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Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

[Xingyu Chen]

Hi, Julius

On 2020/3/12 3:24, Julius Werner wrote:
>> - *_INIT and *GETTIMEOUT.      Although your driver does not need them, could you take them as options in your driver ?
> The driver already has SMCWD_INFO which is used during probe to
> retrieve the minimum and maximum timeout values supported by the
> hardware at probe time. Maybe it would make sense to rename that to
> INIT (which would still return those values, but can also do whatever
> initialization needs to be done in TF)?
Yes，INIT would make sense for me.
> GETTIMELEFT I agree we can
> implement optionally, and other platforms would just return a
> PSCI_RET_NOT_SUPPORTED for that.
>
>> - *_RESETNOW.      It is used to reset the system right now, similar to your SOFT RESET. could you reserve an operation index in ATF ?
> Just curious, why do you need this? Shouldn't you use the PSCI
> standard SYSTEM_RESET SMC for that? (If you want to control exactly
> how the platform is reset, you could also use SYSTEM_RESET2 with a
> vendor-defined reset_type.)
I just wanted it to be compatible with other OS，and I  think it over, 
maybe I can also use the
PSCI interface to execuate the system reset on the other OS. Anyway, 
please ignore this request.

Thanks.
>
> .

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