[v2,2/2] watchdog: Add new arm_smd_wdt watchdog driver
diff mbox series

Message ID 20200403162742.v2.2.Ia92bb4d4ce84bcefeba1d00aaa1c1e919b6164ef@changeid
State Superseded
Headers show
Series
  • Add a watchdog driver that uses ARM Secure Monitor Calls.
Related show

Commit Message

Evan Benn April 3, 2020, 5:29 a.m. UTC
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 v3:
- Add optional get_timeleft op
- change name to arm_smc_wdt

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/arm_smc_wdt.c | 181 +++++++++++++++++++++++++++++++++
 5 files changed, 197 insertions(+)
 create mode 100644 drivers/watchdog/arm_smc_wdt.c

Comments

Guenter Roeck April 3, 2020, 6 a.m. UTC | #1
On Fri, Apr 03, 2020 at 04:29:00PM +1100, Evan Benn wrote:
> 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>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Guenter
Julius Werner April 3, 2020, 10:56 p.m. UTC | #2
> +       wdd->info = &smcwd_info;
> +       /* get_timeleft is optional */
> +       if (smcwd_call(SMCWD_GET_TIMELEFT, 0, NULL))

How is this supposed to work? A firmware that implements this call
would return the time left here which may not be 0 (maybe the watchdog
was already primed by the bootloader or whatever), so smcwd_call()
would interpret it as an error.

I think the cleanest solution would be to stick to the same return
codes in a0 and use a1 to report the time left when a0 is
PSCI_SUCCESS. This is more consistent with SMCWD_INIT too.
Evan Benn April 4, 2020, 1 a.m. UTC | #3
On Sat, Apr 4, 2020 at 9:56 AM Julius Werner <jwerner@chromium.org> wrote:
>
> > +       wdd->info = &smcwd_info;
> > +       /* get_timeleft is optional */
> > +       if (smcwd_call(SMCWD_GET_TIMELEFT, 0, NULL))
>
> How is this supposed to work? A firmware that implements this call
> would return the time left here which may not be 0 (maybe the watchdog
> was already primed by the bootloader or whatever), so smcwd_call()
> would interpret it as an error.
>
> I think the cleanest solution would be to stick to the same return
> codes in a0 and use a1 to report the time left when a0 is
> PSCI_SUCCESS. This is more consistent with SMCWD_INIT too.

Yes you are right, I have the wrong return code in the get_timeleft
implementation. It should use ->a1 for the actual timeleft, a0 is for
the error code.

Here smcwd_call returns the error code, which is NOT_IMPLEMENTED if
the firmware does not implement timeleft. The timeleft itself cannot
return error codes else we would just return that there I guess.

Patch
diff mbox series

diff --git a/MAINTAINERS b/MAINTAINERS
index af8842b998a93..2ec83d4c1032f 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 4db223dbc5499..b5117d46c1d96 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -467,6 +467,7 @@  CONFIG_QCOM_SPMI_TEMP_ALARM=m
 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 9ea2b43d4b012..2a44af10d9beb 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -859,6 +859,19 @@  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
+	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..ec9d4337dad70 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -93,6 +93,7 @@  obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
 obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
 obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
+obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
 obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o
diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
new file mode 100644
index 0000000000000..468995f776b3c
--- /dev/null
+++ b/drivers/watchdog/arm_smc_wdt.c
@@ -0,0 +1,181 @@ 
+// 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		"arm_smc_wdt"
+#define DRV_VERSION		"1.0"
+
+#define SMCWD_FUNC_ID		0x82003d06
+
+enum smcwd_call {
+	SMCWD_INIT		= 0,
+	SMCWD_SET_TIMEOUT	= 1,
+	SMCWD_ENABLE		= 2,
+	SMCWD_PET		= 3,
+	SMCWD_GET_TIMELEFT	= 4,
+};
+
+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 unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
+{
+	struct arm_smccc_res res;
+
+	smcwd_call(SMCWD_GET_TIMELEFT, 0, &res);
+	return res.a0;
+}
+
+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 const struct watchdog_ops smcwd_timeleft_ops = {
+	.start		= smcwd_start,
+	.stop		= smcwd_stop,
+	.ping		= smcwd_ping,
+	.set_timeout	= smcwd_set_timeout,
+	.get_timeleft	= smcwd_get_timeleft,
+};
+
+static int smcwd_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	int err;
+	struct arm_smccc_res res;
+
+	err = smcwd_call(SMCWD_INIT, 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;
+	/* get_timeleft is optional */
+	if (smcwd_call(SMCWD_GET_TIMELEFT, 0, NULL))
+		wdd->ops = &smcwd_ops;
+	else
+		wdd->ops = &smcwd_timeleft_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 = "mediatek,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);