[PATCH 0/2] Add a watchdog driver that uses ARM Secure Monitor Calls.

[PATCH 0/2] Add a watchdog driver that uses ARM Secure Monitor Calls.

[Evan Benn]

This is currently supported in firmware deployed on oak, hana and elm mt8173
chromebook devices. The kernel driver is written to be a generic SMC
watchdog driver.

Arm Trusted Firmware upstreaming review:
    https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405

Patch to add oak, hana, elm device tree:
    https://lore.kernel.org/linux-arm-kernel/20200110073730.213789-1-hsinyi@chromium.org/
I would like to add the device tree support after the above patch is
accepted.


Evan Benn (1):
  dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

Julius Werner (1):
  watchdog: Add new arm_smc_wdt watchdog driver

 .../bindings/watchdog/arm,smc-wdt.yaml        |  30 +++
 MAINTAINERS                                   |   7 +
 arch/arm64/configs/defconfig                  |   1 +
 drivers/watchdog/Kconfig                      |  12 ++
 drivers/watchdog/Makefile                     |   1 +
 drivers/watchdog/arm_smc_wdt.c                | 191 ++++++++++++++++++
 6 files changed, 242 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
 create mode 100644 drivers/watchdog/arm_smc_wdt.c

-- 
2.25.0.265.gbab2e86ba0-goog

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

[Evan Benn]

This watchdog can be used on ARM systems with a Secure
Monitor firmware to forward watchdog operations to
firmware via a Secure Monitor Call.

Signed-off-by: Evan Benn <evanbenn@chromium.org>
---

 .../bindings/watchdog/arm,smc-wdt.yaml        | 30 +++++++++++++++++++
 MAINTAINERS                                   |  6 ++++
 2 files changed, 36 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml

diff --git a/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
new file mode 100644
index 000000000000..5170225b0c98
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/arm,smc-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM Secure Monitor Call based watchdog
+
+allOf:
+  - $ref: "watchdog.yaml#"
+
+maintainers:
+  - Julius Werner <jwerner@chromium.org>
+
+properties:
+  compatible:
+    enum:
+      - arm,smc-wdt
+
+required:
+  - compatible
+
+examples:
+  - |
+    watchdog {
+      compatible = "arm,smc-wdt";
+      timeout-sec = <15>;
+    };
+
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index e48ab79879ac..5c45536e1177 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1421,6 +1421,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/interrupt-controller/amazon,al-fic.txt
 F:	drivers/irqchip/irq-al-fic.c
 
+ARM SMC WATCHDOG DRIVER
+M:	Julius Werner <jwerner@chromium.org>
+R:	Evan Benn <evanbenn@chromium.org>
+S:	Maintained
+F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
+
 ARM SMMU DRIVERS
 M:	Will Deacon <will@kernel.org>
 R:	Robin Murphy <robin.murphy@arm.com>
-- 
2.25.0.265.gbab2e86ba0-goog

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

[Rob Herring]

On Fri, Feb 14, 2020 at 05:26:36PM +1100, Evan Benn wrote:
> This watchdog can be used on ARM systems with a Secure
> Monitor firmware to forward watchdog operations to
> firmware via a Secure Monitor Call.
> 
> Signed-off-by: Evan Benn <evanbenn@chromium.org>
> ---
> 
>  .../bindings/watchdog/arm,smc-wdt.yaml        | 30 +++++++++++++++++++
>  MAINTAINERS                                   |  6 ++++
>  2 files changed, 36 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> new file mode 100644
> index 000000000000..5170225b0c98
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/watchdog/arm,smc-wdt.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ARM Secure Monitor Call based watchdog

You are not the first 'watchdog in firmware accessed via an SMC call'. 
Is there some more detail about what implementation this is? Part of 
TF-A? Defined by some spec (I can dream)?

> +
> +allOf:
> +  - $ref: "watchdog.yaml#"
> +
> +maintainers:
> +  - Julius Werner <jwerner@chromium.org>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - arm,smc-wdt
> +
> +required:
> +  - compatible
> +
> +examples:
> +  - |
> +    watchdog {

I'd expect this to be a child of whatever firmware implements this 
function.

> +      compatible = "arm,smc-wdt";
> +      timeout-sec = <15>;
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e48ab79879ac..5c45536e1177 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1421,6 +1421,12 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/interrupt-controller/amazon,al-fic.txt
>  F:	drivers/irqchip/irq-al-fic.c
>  
> +ARM SMC WATCHDOG DRIVER
> +M:	Julius Werner <jwerner@chromium.org>
> +R:	Evan Benn <evanbenn@chromium.org>
> +S:	Maintained
> +F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
> +
>  ARM SMMU DRIVERS
>  M:	Will Deacon <will@kernel.org>
>  R:	Robin Murphy <robin.murphy@arm.com>
> -- 
> 2.25.0.265.gbab2e86ba0-goog
> 

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

[Julius Werner]

> You are not the first 'watchdog in firmware accessed via an SMC call'.
> Is there some more detail about what implementation this is? Part of
> TF-A? Defined by some spec (I can dream)?

This is just some random implementation written by me because we
needed one. I would like it to be the new generic implementation, but
it sounds like people here prefer the naming to be MediaTek specific
(at least for now). The other SMC watchdog we're aware of is
imx_sc_wdt but unfortunately that seems to hardcode platform-specific
details in the interface (at least in the pretimeout SMC) so we can't
just expand that. With this driver I tried to directly wrap the kernel
watchdog interface so it should be platform-agnostic and possible to
expand this driver to other platforms later if desired. The SMC
function ID would still always have to be platform-specific,
unfortunately (but we could pass it in through the device tree), since
the Arm SMC spec doesn't really leave any room for OS-generic SMCs
like this.

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

[Guenter Roeck]

On Wed, Feb 19, 2020 at 03:04:54PM -0800, Julius Werner wrote:
> > You are not the first 'watchdog in firmware accessed via an SMC call'.
> > Is there some more detail about what implementation this is? Part of
> > TF-A? Defined by some spec (I can dream)?
> 
> This is just some random implementation written by me because we
> needed one. I would like it to be the new generic implementation, but
> it sounds like people here prefer the naming to be MediaTek specific
> (at least for now). The other SMC watchdog we're aware of is
> imx_sc_wdt but unfortunately that seems to hardcode platform-specific

There is one more pending, for Meson SMC.

https://patchwork.kernel.org/project/linux-watchdog/list/?series=227733

Unfortunately it uses Meson firmware API functions, though it has pretty
much the same functionality since those ultimately end up calling
arm_smccc_smc().

Guenter

> details in the interface (at least in the pretimeout SMC) so we can't
> just expand that. With this driver I tried to directly wrap the kernel
> watchdog interface so it should be platform-agnostic and possible to
> expand this driver to other platforms later if desired. The SMC
> function ID would still always have to be platform-specific,
> unfortunately (but we could pass it in through the device tree), since
> the Arm SMC spec doesn't really leave any room for OS-generic SMCs
> like this.

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

[Evan Benn]

Dear Xingyu,

Could this driver also cover your usecase? I am not familiar with
meson, but it seems like the meson calls could
be replaced with arm_smccc calls. Then this driver will cover both
chips. I am not sure if your firmware is upstream
somewhere, but this might be adapted;
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405

Thanks


On Thu, Feb 20, 2020 at 10:20 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Wed, Feb 19, 2020 at 03:04:54PM -0800, Julius Werner wrote:
> > > You are not the first 'watchdog in firmware accessed via an SMC call'.
> > > Is there some more detail about what implementation this is? Part of
> > > TF-A? Defined by some spec (I can dream)?
> >
> > This is just some random implementation written by me because we
> > needed one. I would like it to be the new generic implementation, but
> > it sounds like people here prefer the naming to be MediaTek specific
> > (at least for now). The other SMC watchdog we're aware of is
> > imx_sc_wdt but unfortunately that seems to hardcode platform-specific
>
> There is one more pending, for Meson SMC.
>
> https://patchwork.kernel.org/project/linux-watchdog/list/?series=227733
>
> Unfortunately it uses Meson firmware API functions, though it has pretty
> much the same functionality since those ultimately end up calling
> arm_smccc_smc().
>
> Guenter
>
> > details in the interface (at least in the pretimeout SMC) so we can't
> > just expand that. With this driver I tried to directly wrap the kernel
> > watchdog interface so it should be platform-agnostic and possible to
> > expand this driver to other platforms later if desired. The SMC
> > function ID would still always have to be platform-specific,
> > unfortunately (but we could pass it in through the device tree), since
> > the Arm SMC spec doesn't really leave any room for OS-generic SMCs
> > like this.

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

[Guenter Roeck]

On Thu, Feb 20, 2020 at 05:41:09PM +1100, Evan Benn wrote:
> Dear Xingyu,
> 
> Could this driver also cover your usecase? I am not familiar with
> meson, but it seems like the meson calls could
> be replaced with arm_smccc calls. Then this driver will cover both
> chips. I am not sure if your firmware is upstream
> somewhere, but this might be adapted;
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405
> 
FWIW, the Meson driver has more functionality.

Guenter

> Thanks
> 
> 
> On Thu, Feb 20, 2020 at 10:20 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > On Wed, Feb 19, 2020 at 03:04:54PM -0800, Julius Werner wrote:
> > > > You are not the first 'watchdog in firmware accessed via an SMC call'.
> > > > Is there some more detail about what implementation this is? Part of
> > > > TF-A? Defined by some spec (I can dream)?
> > >
> > > This is just some random implementation written by me because we
> > > needed one. I would like it to be the new generic implementation, but
> > > it sounds like people here prefer the naming to be MediaTek specific
> > > (at least for now). The other SMC watchdog we're aware of is
> > > imx_sc_wdt but unfortunately that seems to hardcode platform-specific
> >
> > There is one more pending, for Meson SMC.
> >
> > https://patchwork.kernel.org/project/linux-watchdog/list/?series=227733
> >
> > Unfortunately it uses Meson firmware API functions, though it has pretty
> > much the same functionality since those ultimately end up calling
> > arm_smccc_smc().
> >
> > Guenter
> >
> > > details in the interface (at least in the pretimeout SMC) so we can't
> > > just expand that. With this driver I tried to directly wrap the kernel
> > > watchdog interface so it should be platform-agnostic and possible to
> > > expand this driver to other platforms later if desired. The SMC
> > > function ID would still always have to be platform-specific,
> > > unfortunately (but we could pass it in through the device tree), since
> > > the Arm SMC spec doesn't really leave any room for OS-generic SMCs
> > > like this.

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

[Xingyu Chen]

Hi, Evan

Because the ATF does not define standard wdt index, each vendor defines 
its own index.
So I don't think that the current driver[0] can fully cover my usecases. 
As discussed in your
previous email, the meson wdt driver [1] can use the arm_smccc instead 
of meson_sm_call.

[0]: https://patchwork.kernel.org/patch/11395579/
[1]: https://patchwork.kernel.org/patch/11331271/

Best Regards

On 2020/2/20 14:41, Evan Benn wrote:
> Dear Xingyu,
>
> Could this driver also cover your usecase? I am not familiar with
> meson, but it seems like the meson calls could
> be replaced with arm_smccc calls. Then this driver will cover both
> chips. I am not sure if your firmware is upstream
> somewhere, but this might be adapted;
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405
>
> Thanks
>
>
> On Thu, Feb 20, 2020 at 10:20 AM Guenter Roeck <linux@roeck-us.net> wrote:
>> On Wed, Feb 19, 2020 at 03:04:54PM -0800, Julius Werner wrote:
>>>> You are not the first 'watchdog in firmware accessed via an SMC call'.
>>>> Is there some more detail about what implementation this is? Part of
>>>> TF-A? Defined by some spec (I can dream)?
>>> This is just some random implementation written by me because we
>>> needed one. I would like it to be the new generic implementation, but
>>> it sounds like people here prefer the naming to be MediaTek specific
>>> (at least for now). The other SMC watchdog we're aware of is
>>> imx_sc_wdt but unfortunately that seems to hardcode platform-specific
>> There is one more pending, for Meson SMC.
>>
>> https://patchwork.kernel.org/project/linux-watchdog/list/?series=227733
>>
>> Unfortunately it uses Meson firmware API functions, though it has pretty
>> much the same functionality since those ultimately end up calling
>> arm_smccc_smc().
>>
>> Guenter
>>
>>> details in the interface (at least in the pretimeout SMC) so we can't
>>> just expand that. With this driver I tried to directly wrap the kernel
>>> watchdog interface so it should be platform-agnostic and possible to
>>> expand this driver to other platforms later if desired. The SMC
>>> function ID would still always have to be platform-specific,
>>> unfortunately (but we could pass it in through the device tree), since
>>> the Arm SMC spec doesn't really leave any room for OS-generic SMCs
>>> like this.
> .

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

[Julius Werner]

> Because the ATF does not define standard wdt index, each vendor defines
> its own index.
> So I don't think that the current driver[0] can fully cover my usecases.

I think the best way to solve this would be to put the SMC function ID
as another field into the device tree, so that multiple vendors could
share the same driver even if their firmware interface uses a
different SMC. But they still have to implement the same API for that
SMC, of course, not sure if the Meson driver is suitable for that (but
if it is then I think merging those drivers would be a good idea).

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

[Guenter Roeck]

On Fri, Feb 21, 2020 at 11:41:47AM -0800, Julius Werner wrote:
> > Because the ATF does not define standard wdt index, each vendor defines
> > its own index.
> > So I don't think that the current driver[0] can fully cover my usecases.
> 
> I think the best way to solve this would be to put the SMC function ID
> as another field into the device tree, so that multiple vendors could
> share the same driver even if their firmware interface uses a
> different SMC. But they still have to implement the same API for that
> SMC, of course, not sure if the Meson driver is suitable for that (but
> if it is then I think merging those drivers would be a good idea).

More common would be to have a single driver and multiple compatible
strings. The driver would then pick the SMC function ID from the compatible
string. After all, we'd not only need the SMC function ID; parameters
are also different.

Guenter

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

[Xingyu Chen]

Hi, Julius

On 2020/2/22 3:41, Julius Werner wrote:
>> Because the ATF does not define standard wdt index, each vendor defines
>> its own index.
>> So I don't think that the current driver[0] can fully cover my usecases.
> I think the best way to solve this would be to put the SMC function ID
> as another field into the device tree, so that multiple vendors could
> share the same driver even if their firmware interface uses a
> different SMC. But they still have to implement the same API for that
> SMC, of course, not sure if the Meson driver is suitable for that (but
> if it is then I think merging those drivers would be a good idea).
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.

Best Regards
>
> .

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

[Evan Benn]

Hello,

I think the intention is that this driver talks to a 'standard' arm
smc firmware watchdog call:

https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405

Each device could re-implement that ATF driver to talk to the specific hardware,
and could perhaps use a custom SMCWD_FUNC_ID, defined in the dts.

The goal was to provide an ATF patch and linux driver patch that would
be generic. But the above ATF patch
is only for mt8173. Right now it just specifies an interface. It has
less functionality than your meson driver Xingyu.
If it is not suitable, that is fine.

The above ATF patch is deployed on oak, elm, and hana mt8173
chromebook devices, this driver is intended to support those devices.

Evan


On Sat, Feb 22, 2020 at 3:01 PM Xingyu Chen <xingyu.chen@amlogic.com> wrote:
>
> Hi, Julius
>
> On 2020/2/22 3:41, Julius Werner wrote:
> >> Because the ATF does not define standard wdt index, each vendor defines
> >> its own index.
> >> So I don't think that the current driver[0] can fully cover my usecases.
> > I think the best way to solve this would be to put the SMC function ID
> > as another field into the device tree, so that multiple vendors could
> > share the same driver even if their firmware interface uses a
> > different SMC. But they still have to implement the same API for that
> > SMC, of course, not sure if the Meson driver is suitable for that (but
> > if it is then I think merging those drivers would be a good idea).
> 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.
>
> Best Regards
> >
> > .

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

[Julius Werner]

> 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.)

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
> .

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
> > .

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.)

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.
>
> .

[PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Evan Benn]

From: Julius Werner <jwerner@chromium.org>

This patch adds a stub watchdog driver that can be used on ARM systems
with a Secure Monitor firmware to forward watchdog operations to
firmware via a Secure Monitor Call. This may be useful for platforms
using TrustZone that want the Secure Monitor firmware to have the final
control over the watchdog.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Evan Benn <evanbenn@chromium.org>
---

 MAINTAINERS                    |   1 +
 arch/arm64/configs/defconfig   |   1 +
 drivers/watchdog/Kconfig       |  12 +++
 drivers/watchdog/Makefile      |   1 +
 drivers/watchdog/arm_smc_wdt.c | 191 +++++++++++++++++++++++++++++++++
 5 files changed, 206 insertions(+)
 create mode 100644 drivers/watchdog/arm_smc_wdt.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5c45536e1177..71df3c110fdb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1426,6 +1426,7 @@ M:	Julius Werner <jwerner@chromium.org>
 R:	Evan Benn <evanbenn@chromium.org>
 S:	Maintained
 F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
+F:	drivers/watchdog/arm_smc_wdt.c
 
 ARM SMMU DRIVERS
 M:	Will Deacon <will@kernel.org>
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index b2f667307f82..8527db9e92a6 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -451,6 +451,7 @@ CONFIG_QCOM_TSENS=y
 CONFIG_UNIPHIER_THERMAL=y
 CONFIG_WATCHDOG=y
 CONFIG_ARM_SP805_WATCHDOG=y
+CONFIG_ARM_SMC_WATCHDOG=y
 CONFIG_S3C2410_WATCHDOG=y
 CONFIG_DW_WATCHDOG=y
 CONFIG_SUNXI_WATCHDOG=m
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index cec868f8db3f..0f7f93342051 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -857,6 +857,18 @@ config DIGICOLOR_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called digicolor_wdt.
 
+config ARM_SMC_WATCHDOG
+	tristate "ARM Secure Monitor Call based watchdog support"
+	depends on ARM || ARM64
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for a watchdog timer
+	  implemented by the EL3 Secure Monitor on ARM platforms.
+	  Requires firmware support.
+	  To compile this driver as a module, choose M here: the
+	  module will be called arm_smc_wdt.
+
+
 config LPC18XX_WATCHDOG
 	tristate "LPC18xx/43xx Watchdog"
 	depends on ARCH_LPC18XX || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee352bf3372..a1e6d83a7659 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
 obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
 obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
 obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
+obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
new file mode 100644
index 000000000000..58e7294136ef
--- /dev/null
+++ b/drivers/watchdog/arm_smc_wdt.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARM Secure Monitor Call watchdog driver
+ *
+ * Copyright 2018 The Chromium OS Authors. All rights reserved.
+ *
+ * Julius Werner <jwerner@chromium.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Based on mtk_wdt.c
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+#include <uapi/linux/psci.h>
+
+#define DRV_NAME		"arm_smc_wdt"
+#define DRV_VERSION		"1.0"
+
+#define SMCWD_FUNC_ID		0x82003d06
+
+enum smcwd_call {
+	SMCWD_INFO		= 0,
+	SMCWD_SET_TIMEOUT	= 1,
+	SMCWD_ENABLE		= 2,
+	SMCWD_PET		= 3,
+};
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+static unsigned int timeout;
+
+static int smcwd_call(enum smcwd_call call, unsigned long arg,
+		      struct arm_smccc_res *res)
+{
+	struct arm_smccc_res local_res;
+
+	if (!res)
+		res = &local_res;
+
+	arm_smccc_smc(SMCWD_FUNC_ID, call, arg, 0, 0, 0, 0, 0, res);
+
+	if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
+		return -ENOTSUPP;
+	if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
+		return -EINVAL;
+	if ((int)res->a0 < 0)
+		return -EIO;
+	return res->a0;
+}
+
+static int smcwd_ping(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_PET, 0, NULL);
+}
+
+static int smcwd_set_timeout(struct watchdog_device *wdd,
+				unsigned int timeout)
+{
+	int res;
+
+	res = smcwd_call(SMCWD_SET_TIMEOUT, timeout, NULL);
+	if (!res)
+		wdd->timeout = timeout;
+	return res;
+}
+
+static int smcwd_stop(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_ENABLE, 0, NULL);
+}
+
+static int smcwd_start(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_ENABLE, 1, NULL);
+}
+
+static const struct watchdog_info smcwd_info = {
+	.identity	= DRV_NAME,
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops smcwd_ops = {
+	.owner		= THIS_MODULE,
+	.start		= smcwd_start,
+	.stop		= smcwd_stop,
+	.ping		= smcwd_ping,
+	.set_timeout	= smcwd_set_timeout,
+};
+
+static int smcwd_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	int err;
+	struct arm_smccc_res res;
+
+	err = smcwd_call(SMCWD_INFO, 0, &res);
+	if (err < 0)
+		return err;
+
+	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
+	if (!wdd)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, wdd);
+
+	wdd->info = &smcwd_info;
+	wdd->ops = &smcwd_ops;
+	wdd->timeout = res.a2;
+	wdd->max_timeout = res.a2;
+	wdd->min_timeout = res.a1;
+	wdd->parent = &pdev->dev;
+
+	watchdog_set_nowayout(wdd, nowayout);
+	watchdog_init_timeout(wdd, timeout, &pdev->dev);
+	err = smcwd_set_timeout(wdd, wdd->timeout);
+	if (err)
+		return err;
+
+	err = watchdog_register_device(wdd);
+	if (err)
+		return err;
+
+	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",
+			wdd->timeout, nowayout);
+
+	return 0;
+}
+
+static void smcwd_shutdown(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+
+	if (watchdog_active(wdd))
+		smcwd_stop(wdd);
+}
+
+static int smcwd_remove(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+
+	watchdog_unregister_device(wdd);
+
+	return 0;
+}
+
+static const struct of_device_id smcwd_dt_ids[] = {
+	{ .compatible = "arm,smc-wdt" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
+
+static struct platform_driver smcwd_driver = {
+	.probe		= smcwd_probe,
+	.remove		= smcwd_remove,
+	.shutdown	= smcwd_shutdown,
+	.driver		= {
+		.name		= DRV_NAME,
+		.of_match_table	= smcwd_dt_ids,
+	},
+};
+
+module_platform_driver(smcwd_driver);
+
+module_param(timeout, uint, 0);
+MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
+
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
+MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
+MODULE_VERSION(DRV_VERSION);
-- 
2.25.0.265.gbab2e86ba0-goog

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Enric Balletbo Serra]

Hi Evan and Julius,

Many thanks for sending this upstream, I have some trivial comments,
especially the license one, other than that, the driver looks good to
me.

Missatge de Evan Benn <evanbenn@chromium.org> del dia dv., 14 de febr.
2020 a les 7:28:
>
> From: Julius Werner <jwerner@chromium.org>
>
> This patch adds a stub watchdog driver that can be used on ARM systems
> with a Secure Monitor firmware to forward watchdog operations to
> firmware via a Secure Monitor Call. This may be useful for platforms
> using TrustZone that want the Secure Monitor firmware to have the final
> control over the watchdog.
>
> Signed-off-by: Julius Werner <jwerner@chromium.org>
> Signed-off-by: Evan Benn <evanbenn@chromium.org>
> ---
>
>  MAINTAINERS                    |   1 +
>  arch/arm64/configs/defconfig   |   1 +
>  drivers/watchdog/Kconfig       |  12 +++
>  drivers/watchdog/Makefile      |   1 +
>  drivers/watchdog/arm_smc_wdt.c | 191 +++++++++++++++++++++++++++++++++
>  5 files changed, 206 insertions(+)
>  create mode 100644 drivers/watchdog/arm_smc_wdt.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5c45536e1177..71df3c110fdb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1426,6 +1426,7 @@ M:        Julius Werner <jwerner@chromium.org>
>  R:     Evan Benn <evanbenn@chromium.org>
>  S:     Maintained
>  F:     devicetree/bindings/watchdog/arm,smc-wdt.yaml
> +F:     drivers/watchdog/arm_smc_wdt.c
>
>  ARM SMMU DRIVERS
>  M:     Will Deacon <will@kernel.org>
> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> index b2f667307f82..8527db9e92a6 100644
> --- a/arch/arm64/configs/defconfig
> +++ b/arch/arm64/configs/defconfig
> @@ -451,6 +451,7 @@ CONFIG_QCOM_TSENS=y
>  CONFIG_UNIPHIER_THERMAL=y
>  CONFIG_WATCHDOG=y
>  CONFIG_ARM_SP805_WATCHDOG=y
> +CONFIG_ARM_SMC_WATCHDOG=y
>  CONFIG_S3C2410_WATCHDOG=y
>  CONFIG_DW_WATCHDOG=y
>  CONFIG_SUNXI_WATCHDOG=m
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index cec868f8db3f..0f7f93342051 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -857,6 +857,18 @@ config DIGICOLOR_WATCHDOG
>           To compile this driver as a module, choose M here: the
>           module will be called digicolor_wdt.
>
> +config ARM_SMC_WATCHDOG
> +       tristate "ARM Secure Monitor Call based watchdog support"
> +       depends on ARM || ARM64

Looks like this driver is OF only, so add a dependency on CONFIG_OF

> +       select WATCHDOG_CORE
> +       help
> +         Say Y here to include support for a watchdog timer
> +         implemented by the EL3 Secure Monitor on ARM platforms.
> +         Requires firmware support.
> +         To compile this driver as a module, choose M here: the
> +         module will be called arm_smc_wdt.
> +
> +
>  config LPC18XX_WATCHDOG
>         tristate "LPC18xx/43xx Watchdog"
>         depends on ARCH_LPC18XX || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 2ee352bf3372..a1e6d83a7659 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -92,6 +92,7 @@ obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
>  obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
>  obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
>  obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
> +obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
>  obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
>
>  # X86 (i386 + ia64 + x86_64) Architecture
> diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
> new file mode 100644
> index 000000000000..58e7294136ef
> --- /dev/null
> +++ b/drivers/watchdog/arm_smc_wdt.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * ARM Secure Monitor Call watchdog driver
> + *
> + * Copyright 2018 The Chromium OS Authors. All rights reserved.
> + *
> + * Julius Werner <jwerner@chromium.org>
> + *

When adding new files to the kernel, use the regular Google copyright
header to them. The main reason for this is that there‘s no concept of
“The Chromium OS Authors” outside of Chromium OS project, since it
refers to the AUTHORS file that isn’t bundled with the kernel. [1]

In this case, it should be something like this:

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * ARM Secure Monitor Call watchdog driver
 *
 * Copyright 2020 Google LLC.
 */

See: https://chromium.googlesource.com/chromiumos/docs/+/master/kernel_faq.md

> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * Based on mtk_wdt.c

Remove the license boilerplate, it is implicit in the SPDX tag. The
reasoning is to avoid mismatches like what happens here. You are
licensing the file as GPL-2.0-only but the boilerplate is
GPL-2.0-or-later.

> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/types.h>
> +#include <linux/watchdog.h>
> +#include <uapi/linux/psci.h>
> +
> +#define DRV_NAME               "arm_smc_wdt"
> +#define DRV_VERSION            "1.0"
> +
> +#define SMCWD_FUNC_ID          0x82003d06
> +
> +enum smcwd_call {
> +       SMCWD_INFO              = 0,
> +       SMCWD_SET_TIMEOUT       = 1,
> +       SMCWD_ENABLE            = 2,
> +       SMCWD_PET               = 3,
> +};
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +static unsigned int timeout;
> +
> +static int smcwd_call(enum smcwd_call call, unsigned long arg,
> +                     struct arm_smccc_res *res)
> +{
> +       struct arm_smccc_res local_res;
> +
> +       if (!res)
> +               res = &local_res;
> +
> +       arm_smccc_smc(SMCWD_FUNC_ID, call, arg, 0, 0, 0, 0, 0, res);
> +
> +       if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)

Is this cast really needed?

> +               return -ENOTSUPP;
> +       if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)

ditto
> +               return -EINVAL;
> +       if ((int)res->a0 < 0)

ditto
> +               return -EIO;
> +       return res->a0;
> +}
> +
> +static int smcwd_ping(struct watchdog_device *wdd)
> +{
> +       return smcwd_call(SMCWD_PET, 0, NULL);
> +}
> +
> +static int smcwd_set_timeout(struct watchdog_device *wdd,
> +                               unsigned int timeout)

nit: Alignment should match open parenthesis ( if you want to follow
what checkpatch says with the --strict option )

> +{
> +       int res;
> +
> +       res = smcwd_call(SMCWD_SET_TIMEOUT, timeout, NULL);
> +       if (!res)
> +               wdd->timeout = timeout;
> +       return res;
> +}
> +
> +static int smcwd_stop(struct watchdog_device *wdd)
> +{
> +       return smcwd_call(SMCWD_ENABLE, 0, NULL);
> +}
> +
> +static int smcwd_start(struct watchdog_device *wdd)
> +{
> +       return smcwd_call(SMCWD_ENABLE, 1, NULL);
> +}
> +
> +static const struct watchdog_info smcwd_info = {
> +       .identity       = DRV_NAME,
> +       .options        = WDIOF_SETTIMEOUT |
> +                         WDIOF_KEEPALIVEPING |
> +                         WDIOF_MAGICCLOSE,
> +};
> +
> +static const struct watchdog_ops smcwd_ops = {
> +       .owner          = THIS_MODULE,
> +       .start          = smcwd_start,
> +       .stop           = smcwd_stop,
> +       .ping           = smcwd_ping,
> +       .set_timeout    = smcwd_set_timeout,
> +};
> +
> +static int smcwd_probe(struct platform_device *pdev)
> +{
> +       struct watchdog_device *wdd;
> +       int err;
> +       struct arm_smccc_res res;
> +
> +       err = smcwd_call(SMCWD_INFO, 0, &res);
> +       if (err < 0)
> +               return err;
> +
> +       wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
> +       if (!wdd)
> +               return -ENOMEM;
> +
> +       platform_set_drvdata(pdev, wdd);
> +
> +       wdd->info = &smcwd_info;
> +       wdd->ops = &smcwd_ops;
> +       wdd->timeout = res.a2;
> +       wdd->max_timeout = res.a2;
> +       wdd->min_timeout = res.a1;
> +       wdd->parent = &pdev->dev;
> +
> +       watchdog_set_nowayout(wdd, nowayout);
> +       watchdog_init_timeout(wdd, timeout, &pdev->dev);
> +       err = smcwd_set_timeout(wdd, wdd->timeout);
> +       if (err)
> +               return err;
> +
> +       err = watchdog_register_device(wdd);
> +       if (err)
> +               return err;
> +
> +       dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",
> +                       wdd->timeout, nowayout);
> +
> +       return 0;
> +}
> +
> +static void smcwd_shutdown(struct platform_device *pdev)
> +{
> +       struct watchdog_device *wdd = platform_get_drvdata(pdev);
> +
> +       if (watchdog_active(wdd))
> +               smcwd_stop(wdd);
> +}
> +
> +static int smcwd_remove(struct platform_device *pdev)
> +{
> +       struct watchdog_device *wdd = platform_get_drvdata(pdev);
> +
> +       watchdog_unregister_device(wdd);
> +
> +       return 0;
> +}
> +
> +static const struct of_device_id smcwd_dt_ids[] = {
> +       { .compatible = "arm,smc-wdt" },
> +       { /* sentinel */ }

nit: not sure about this subsystem, but usually the /* sentinel */
word is removed because is really trivial what is { } at the end of
struct.

> +};
> +MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
> +
> +static struct platform_driver smcwd_driver = {
> +       .probe          = smcwd_probe,
> +       .remove         = smcwd_remove,
> +       .shutdown       = smcwd_shutdown,
> +       .driver         = {
> +               .name           = DRV_NAME,
> +               .of_match_table = smcwd_dt_ids,
> +       },
> +};
> +
> +module_platform_driver(smcwd_driver);
> +
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
> +
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +                       __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
> +MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
> +MODULE_VERSION(DRV_VERSION);
> --
> 2.25.0.265.gbab2e86ba0-goog
>

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Guenter Roeck]

On 2/13/20 10:26 PM, Evan Benn wrote:
> From: Julius Werner <jwerner@chromium.org>
> 
> This patch adds a stub watchdog driver that can be used on ARM systems

 From kernel perspective, this is not a "stub" driver. A stub driver is one
that doesn't do anything.

> with a Secure Monitor firmware to forward watchdog operations to
> firmware via a Secure Monitor Call. This may be useful for platforms
> using TrustZone that want the Secure Monitor firmware to have the final
> control over the watchdog.
> 

As written, one would assume this to work on all systems implementing
ARM secure firmware, which is not the case. Please select a different
name, and provide information about the systems where this is actually
supported.

If it happens to be standardized, we will need a reference to the standard
supported. This needs to distinguish from IMX_SC_WDT, which also supports
a secure monitor based watchdog (but doesn't claim to be generic).

> Signed-off-by: Julius Werner <jwerner@chromium.org>
> Signed-off-by: Evan Benn <evanbenn@chromium.org>

I won't comment on items already covered by Enric. Please address those as well.

> ---
> 
>   MAINTAINERS                    |   1 +
>   arch/arm64/configs/defconfig   |   1 +
>   drivers/watchdog/Kconfig       |  12 +++
>   drivers/watchdog/Makefile      |   1 +
>   drivers/watchdog/arm_smc_wdt.c | 191 +++++++++++++++++++++++++++++++++
>   5 files changed, 206 insertions(+)
>   create mode 100644 drivers/watchdog/arm_smc_wdt.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5c45536e1177..71df3c110fdb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1426,6 +1426,7 @@ M:	Julius Werner <jwerner@chromium.org>
>   R:	Evan Benn <evanbenn@chromium.org>
>   S:	Maintained
>   F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
> +F:	drivers/watchdog/arm_smc_wdt.c
>   
>   ARM SMMU DRIVERS
>   M:	Will Deacon <will@kernel.org>
> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> index b2f667307f82..8527db9e92a6 100644
> --- a/arch/arm64/configs/defconfig
> +++ b/arch/arm64/configs/defconfig
> @@ -451,6 +451,7 @@ CONFIG_QCOM_TSENS=y
>   CONFIG_UNIPHIER_THERMAL=y
>   CONFIG_WATCHDOG=y
>   CONFIG_ARM_SP805_WATCHDOG=y
> +CONFIG_ARM_SMC_WATCHDOG=y
>   CONFIG_S3C2410_WATCHDOG=y
>   CONFIG_DW_WATCHDOG=y
>   CONFIG_SUNXI_WATCHDOG=m
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index cec868f8db3f..0f7f93342051 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -857,6 +857,18 @@ config DIGICOLOR_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called digicolor_wdt.
>   
> +config ARM_SMC_WATCHDOG
> +	tristate "ARM Secure Monitor Call based watchdog support"
> +	depends on ARM || ARM64

This also depends on HAVE_ARM_SMCCC.

> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include support for a watchdog timer
> +	  implemented by the EL3 Secure Monitor on ARM platforms.
> +	  Requires firmware support.
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called arm_smc_wdt.
> +
> +
Extra empty line.

>   config LPC18XX_WATCHDOG
>   	tristate "LPC18xx/43xx Watchdog"
>   	depends on ARCH_LPC18XX || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 2ee352bf3372..a1e6d83a7659 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -92,6 +92,7 @@ obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
>   obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
>   obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
>   obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
> +obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
>   obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
>   
>   # X86 (i386 + ia64 + x86_64) Architecture
> diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
> new file mode 100644
> index 000000000000..58e7294136ef
> --- /dev/null
> +++ b/drivers/watchdog/arm_smc_wdt.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * ARM Secure Monitor Call watchdog driver
> + *
> + * Copyright 2018 The Chromium OS Authors. All rights reserved.
> + *
> + * Julius Werner <jwerner@chromium.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * Based on mtk_wdt.c
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/types.h>
> +#include <linux/watchdog.h>
> +#include <uapi/linux/psci.h>
> +
> +#define DRV_NAME		"arm_smc_wdt"
> +#define DRV_VERSION		"1.0"
> +
> +#define SMCWD_FUNC_ID		0x82003d06
> +
> +enum smcwd_call {
> +	SMCWD_INFO		= 0,
> +	SMCWD_SET_TIMEOUT	= 1,
> +	SMCWD_ENABLE		= 2,
> +	SMCWD_PET		= 3,
> +};
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +static unsigned int timeout;
> +
> +static int smcwd_call(enum smcwd_call call, unsigned long arg,
> +		      struct arm_smccc_res *res)
> +{
> +	struct arm_smccc_res local_res;
> +
> +	if (!res)
> +		res = &local_res;
> +
> +	arm_smccc_smc(SMCWD_FUNC_ID, call, arg, 0, 0, 0, 0, 0, res);
> +
> +	if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
> +		return -ENOTSUPP;

-ENODEV would be better here.

> +	if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
> +		return -EINVAL;
> +	if ((int)res->a0 < 0)
> +		return -EIO;

Yes, those typecasts are indeed unnecessary.

> +	return res->a0;
> +}
> +
> +static int smcwd_ping(struct watchdog_device *wdd)
> +{
> +	return smcwd_call(SMCWD_PET, 0, NULL);
> +}
> +
> +static int smcwd_set_timeout(struct watchdog_device *wdd,
> +				unsigned int timeout)
> +{
> +	int res;
> +
> +	res = smcwd_call(SMCWD_SET_TIMEOUT, timeout, NULL);
> +	if (!res)
> +		wdd->timeout = timeout;
> +	return res;
> +}
> +
> +static int smcwd_stop(struct watchdog_device *wdd)
> +{
> +	return smcwd_call(SMCWD_ENABLE, 0, NULL);
> +}
> +
> +static int smcwd_start(struct watchdog_device *wdd)
> +{
> +	return smcwd_call(SMCWD_ENABLE, 1, NULL);
> +}
> +
> +static const struct watchdog_info smcwd_info = {
> +	.identity	= DRV_NAME,
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE,
> +};
> +
> +static const struct watchdog_ops smcwd_ops = {
> +	.owner		= THIS_MODULE,

Not necessary, and will result in a static analyzer warning.

> +	.start		= smcwd_start,
> +	.stop		= smcwd_stop,
> +	.ping		= smcwd_ping,
> +	.set_timeout	= smcwd_set_timeout,
> +};
> +
> +static int smcwd_probe(struct platform_device *pdev)
> +{
> +	struct watchdog_device *wdd;
> +	int err;
> +	struct arm_smccc_res res;
> +
> +	err = smcwd_call(SMCWD_INFO, 0, &res);
> +	if (err < 0)
> +		return err;
> +
> +	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
> +	if (!wdd)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, wdd);
> +
> +	wdd->info = &smcwd_info;
> +	wdd->ops = &smcwd_ops;
> +	wdd->timeout = res.a2;
> +	wdd->max_timeout = res.a2;
> +	wdd->min_timeout = res.a1;
> +	wdd->parent = &pdev->dev;
> +
> +	watchdog_set_nowayout(wdd, nowayout);
> +	watchdog_init_timeout(wdd, timeout, &pdev->dev);
> +	err = smcwd_set_timeout(wdd, wdd->timeout);
> +	if (err)
> +		return err;
> +
> +	err = watchdog_register_device(wdd);

devm_watchdog_register_device() should work here.

> +	if (err)
> +		return err;
> +
> +	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",

The watchdog is not enabled here, it is only registered.

> +			wdd->timeout, nowayout);
> +
> +	return 0;
> +}
> +
> +static void smcwd_shutdown(struct platform_device *pdev)
> +{
> +	struct watchdog_device *wdd = platform_get_drvdata(pdev);
> +
> +	if (watchdog_active(wdd))
> +		smcwd_stop(wdd);
> +}
> +
Please use watchdog_stop_on_reboot().

> +static int smcwd_remove(struct platform_device *pdev)
> +{
> +	struct watchdog_device *wdd = platform_get_drvdata(pdev);
> +
> +	watchdog_unregister_device(wdd);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id smcwd_dt_ids[] = {
> +	{ .compatible = "arm,smc-wdt" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
> +
> +static struct platform_driver smcwd_driver = {
> +	.probe		= smcwd_probe,
> +	.remove		= smcwd_remove,
> +	.shutdown	= smcwd_shutdown,
> +	.driver		= {
> +		.name		= DRV_NAME,
> +		.of_match_table	= smcwd_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(smcwd_driver);
> +
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
> +
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
> +MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
> +MODULE_VERSION(DRV_VERSION);
> 

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Julius Werner]

> > with a Secure Monitor firmware to forward watchdog operations to
> > firmware via a Secure Monitor Call. This may be useful for platforms
> > using TrustZone that want the Secure Monitor firmware to have the final
> > control over the watchdog.
> >
>
> As written, one would assume this to work on all systems implementing
> ARM secure firmware, which is not the case. Please select a different
> name, and provide information about the systems where this is actually
> supported.
>
> If it happens to be standardized, we will need a reference to the standard
> supported. This needs to distinguish from IMX_SC_WDT, which also supports
> a secure monitor based watchdog (but doesn't claim to be generic).

Back when I wrote this I was hoping it could be something that other
platforms can pick up if they want to, but that hasn't happened yet
and the code on the Trusted Firmware side is still MediaTek-specific.
Unfortunately Arm doesn't make it easy to write generic SMC interfaces
and my attempts to change that haven't been very fruitful for now. So
yes, probably makes sense to treat this as MediaTek-specific for now,
we can still consider expanding it later if there's interest from
other platforms. (I would like to avoid every vendor writing their own
driver and SMC interface for this, although looking at that IMX driver
it seems that we're already there.)

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Evan Benn]

> > As written, one would assume this to work on all systems implementing
> > ARM secure firmware, which is not the case. Please select a different
> > name, and provide information about the systems where this is actually
> > supported.

> Back when I wrote this I was hoping it could be something that other
> platforms can pick up if they want to, but that hasn't happened yet
> and the code on the Trusted Firmware side is still MediaTek-specific.

Thanks, I will re-word as mediatek,mt8173-smc-wdt, and address other comments.
In the event this does become a standard arm watchdog interface, I assume
but do not know that it will be straightforward to change the name here.

I am not sure how to proceed with modifying Julius' authored patch in
kernel preferred way.
I can add myself as co-authored-by and modify patch 2, or add a patch
3 to make preferred changes.

I will use approach 2 for now unless otherwise advised.

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Evan Benn]

> > +     if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
> > +             return -ENOTSUPP;
>
> -ENODEV would be better here.
>
> > +     if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
> > +             return -EINVAL;
> > +     if ((int)res->a0 < 0)
> > +             return -EIO;

In fixing this I found drivers/firmware/psci/psci.c:145
Which also translates psci codes to errno codes, but uses EOPNOTSUPP:

    switch (errno) {
    case PSCI_RET_SUCCESS:
        return 0;
    case PSCI_RET_NOT_SUPPORTED:
        return -EOPNOTSUPP;
    case PSCI_RET_INVALID_PARAMS:
    case PSCI_RET_INVALID_ADDRESS:
        return -EINVAL;
    case PSCI_RET_DENIED:
        return -EPERM;
    };

    return -EINVAL;

Are these more appropriate?

Evan

Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Guenter Roeck]

On Thu, Feb 20, 2020 at 05:50:03PM +1100, Evan Benn wrote:
> > > +     if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
> > > +             return -ENOTSUPP;
> >
> > -ENODEV would be better here.
> >
> > > +     if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
> > > +             return -EINVAL;
> > > +     if ((int)res->a0 < 0)
> > > +             return -EIO;
> 
> In fixing this I found drivers/firmware/psci/psci.c:145
> Which also translates psci codes to errno codes, but uses EOPNOTSUPP:
> 
>     switch (errno) {
>     case PSCI_RET_SUCCESS:
>         return 0;
>     case PSCI_RET_NOT_SUPPORTED:
>         return -EOPNOTSUPP;
>     case PSCI_RET_INVALID_PARAMS:
>     case PSCI_RET_INVALID_ADDRESS:
>         return -EINVAL;
>     case PSCI_RET_DENIED:
>         return -EPERM;
>     };
> 
>     return -EINVAL;
> 
> Are these more appropriate?
> 

It is customary for driver probe functions to return -ENODEV if the
device is not supported. I don't see a reason why this driver should
behave any different. "but this other driver does it" is never a good
argument.

Having said that, yet, with the exception of -EOPNOTSUPP the other
return values would be more appropriate.

Guenter