[PATCH v2 0/2] Add a watchdog driver that uses ARM Secure Monitor Calls.

[PATCH v2 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.

Changes in v2:
- Change name arm > mt8173
- use watchdog_stop_on_reboot
- use watchdog_stop_on_unregister
- use devm_watchdog_register_device
- remove smcwd_shutdown, smcwd_remove
- change error codes

Evan Benn (1):
  dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

Julius Werner (1):
  watchdog: Add new mt8173_smc_wdt watchdog driver

 .../bindings/watchdog/mt8173,smc-wdt.yaml     |  30 ++++
 MAINTAINERS                                   |   7 +
 arch/arm64/configs/defconfig                  |   1 +
 drivers/watchdog/Kconfig                      |  13 ++
 drivers/watchdog/Makefile                     |   1 +
 drivers/watchdog/mt8173_smc_wdt.c             | 160 ++++++++++++++++++
 6 files changed, 212 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
 create mode 100644 drivers/watchdog/mt8173_smc_wdt.c

-- 
2.25.0.265.gbab2e86ba0-goog

[PATCH v2 1/2] dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

[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>
---

Changes in v2:
- Change name arm > mt8173

 .../bindings/watchdog/mt8173,smc-wdt.yaml     | 30 +++++++++++++++++++
 MAINTAINERS                                   |  6 ++++
 2 files changed, 36 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml

diff --git a/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml b/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
new file mode 100644
index 0000000000000..ff45e13bc548b
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/mt8173,smc-wdt.yaml#
+$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:
+      - mt8173,smc-wdt
+
+required:
+  - compatible
+
+examples:
+  - |
+    watchdog {
+      compatible = "mt8173,smc-wdt";
+      timeout-sec = <15>;
+    };
+
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index e48ab79879ace..59e8779363c12 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/mt8173,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

[PATCH v2 2/2] watchdog: Add new mt8173_smc_wdt watchdog driver

[Evan Benn]

From: Julius Werner <jwerner@chromium.org>

This patch adds a watchdog driver that can be used on ARM systems
with the appropriate watchdog implemented in Secure Monitor firmware.
The driver communicates with 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.

This is implemented on mt8173 chromebook devices oak, elm and hana in
arm trusted firmware file plat/mediatek/mt8173/drivers/wdt/wdt.c.

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

Changes in v2:
- use watchdog_stop_on_reboot
- use watchdog_stop_on_unregister
- use devm_watchdog_register_device
- remove smcwd_shutdown, smcwd_remove
- change error codes

 MAINTAINERS                       |   1 +
 arch/arm64/configs/defconfig      |   1 +
 drivers/watchdog/Kconfig          |  13 +++
 drivers/watchdog/Makefile         |   1 +
 drivers/watchdog/mt8173_smc_wdt.c | 160 ++++++++++++++++++++++++++++++
 5 files changed, 176 insertions(+)
 create mode 100644 drivers/watchdog/mt8173_smc_wdt.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 59e8779363c12..94e295e16e128 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/mt8173,smc-wdt.yaml
+F:	drivers/watchdog/mt8173_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 b2f667307f829..11d94c9258b79 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_MT8173_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 cec868f8db3f9..b4e55db7a4dcf 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -857,6 +857,19 @@ config DIGICOLOR_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called digicolor_wdt.
 
+config MT8173_SMC_WATCHDOG
+	tristate "ARM Secure Monitor Call based watchdog support"
+	depends on ARM || ARM64
+	depends on OF
+	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.
+
 config LPC18XX_WATCHDOG
 	tristate "LPC18xx/43xx Watchdog"
 	depends on ARCH_LPC18XX || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee352bf3372d..d1381234892ef 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-$(CONFIG_MT8173_SMC_WATCHDOG) += mt8173_smc_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
diff --git a/drivers/watchdog/mt8173_smc_wdt.c b/drivers/watchdog/mt8173_smc_wdt.c
new file mode 100644
index 0000000000000..681aa42c7d277
--- /dev/null
+++ b/drivers/watchdog/mt8173_smc_wdt.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARM Secure Monitor Call watchdog driver
+ *
+ * Copyright 2020 Google LLC.
+ * Julius Werner <jwerner@chromium.org>
+ * 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		"mt8173_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 (res->a0 == PSCI_RET_NOT_SUPPORTED)
+		return -ENODEV;
+	if (res->a0 == PSCI_RET_INVALID_PARAMS)
+		return -EINVAL;
+	if (res->a0 != PSCI_RET_SUCCESS)
+		return -EIO;
+	return 0;
+}
+
+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 = {
+	.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_stop_on_reboot(wdd);
+	watchdog_stop_on_unregister(wdd);
+	watchdog_set_nowayout(wdd, nowayout);
+	watchdog_init_timeout(wdd, timeout, &pdev->dev);
+	err = smcwd_set_timeout(wdd, wdd->timeout);
+	if (err)
+		return err;
+
+	err = devm_watchdog_register_device(&pdev->dev, wdd);
+	if (err)
+		return err;
+
+	dev_info(&pdev->dev, "Watchdog registered (timeout=%d sec, nowayout=%d)\n",
+		 wdd->timeout, nowayout);
+
+	return 0;
+}
+
+static const struct of_device_id smcwd_dt_ids[] = {
+	{ .compatible = "mt8173,smc-wdt" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
+
+static struct platform_driver smcwd_driver = {
+	.probe		= smcwd_probe,
+	.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 v2 1/2] dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

[Rob Herring]

On Thu, Feb 20, 2020 at 11:38 PM Evan Benn <evanbenn@chromium.org> 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>
> ---
>
> Changes in v2:
> - Change name arm > mt8173
>
>  .../bindings/watchdog/mt8173,smc-wdt.yaml     | 30 +++++++++++++++++++
>  MAINTAINERS                                   |  6 ++++
>  2 files changed, 36 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
>
> diff --git a/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml b/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
> new file mode 100644
> index 0000000000000..ff45e13bc548b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/watchdog/mt8173,smc-wdt.yaml
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/watchdog/mt8173,smc-wdt.yaml#
> +$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:
> +      - mt8173,smc-wdt

compatible strings are in the form <vendor>,<device>. 'mt8173' is not a vendor.

> +
> +required:
> +  - compatible
> +
> +examples:
> +  - |
> +    watchdog {

This should be a child of some Mediatek firmware node. I assume
watchdog is not the *only* function.

> +      compatible = "mt8173,smc-wdt";
> +      timeout-sec = <15>;
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e48ab79879ace..59e8779363c12 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/mt8173,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 v2 1/2] dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

[Evan Benn]

Thanks Rob

> This should be a child of some Mediatek firmware node. I assume
> watchdog is not the *only* function.

I am not quite sure what you mean, do you intend this:

 firmware {
   watchdog {
     ...
   }
}

I do not have a deep understanding of devicetree yet, can you point me
to anything that will help me understand
the consequences of that change?

Thanks

Evan

Re: [PATCH v2 1/2] dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

[Rob Herring]

On Tue, Feb 25, 2020 at 6:15 PM Evan Benn <evanbenn@chromium.org> wrote:
>
> Thanks Rob
>
> > This should be a child of some Mediatek firmware node. I assume
> > watchdog is not the *only* function.
>
> I am not quite sure what you mean, do you intend this:
>
>  firmware {
>    watchdog {

Not quite. /firmware is generic container. I'd expect another layer in
the middle for the overall set of Mediatek firmware behind smc calls.
Look at 'xlnx,zynqmp-firmware' for an example.

Rob

Re: [PATCH v2 1/2] dt-bindings: watchdog: Add mt8173,smc-wdt watchdog

[Julius Werner]

> Not quite. /firmware is generic container. I'd expect another layer in
> the middle for the overall set of Mediatek firmware behind smc calls.
> Look at 'xlnx,zynqmp-firmware' for an example.

There are no other MediaTek firmware interfaces described in the
device tree on those platforms. Is it okay if we just call it
/firmware/watchdog in that case?