Re: [PATCH v6 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Guenter Roeck <linux@roeck-us.net>]

On 5/4/20 8:13 PM, 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>

> 
> ---
> 
> Changes in v6:
> - Use default arm,smc-id value if non provided by dt
> 
> Changes in v5:
> - Make timeleft return 0 on error
> - Use type punning on smc_func_id to save an alloc
> - Change compatible to arm,smc-wdt
> 
> Changes in v4:
> - Get smc-id from of property
> - Return a1 instead of a0 in timeleft
> 
> 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 | 188 +++++++++++++++++++++++++++++++++
>  5 files changed, 204 insertions(+)
>  create mode 100644 drivers/watchdog/arm_smc_wdt.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0f2b39767bfa9..2b782bbff200a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1462,6 +1462,7 @@ 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 24e534d850454..0619df80f7575 100644
> --- a/arch/arm64/configs/defconfig
> +++ b/arch/arm64/configs/defconfig
> @@ -513,6 +513,7 @@ CONFIG_UNIPHIER_THERMAL=y
>  CONFIG_WATCHDOG=y
>  CONFIG_ARM_SP805_WATCHDOG=y
>  CONFIG_ARM_SBSA_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 0663c604bd642..c440b576d23bf 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -867,6 +867,19 @@ 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 6de2e4ceef190..97bed1d3d97cb 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -94,6 +94,7 @@ 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..8f3d0c3a005fb
> --- /dev/null
> +++ b/drivers/watchdog/arm_smc_wdt.c
> @@ -0,0 +1,188 @@
> +// 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"
> +
> +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(struct watchdog_device *wdd, 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((u32)(uintptr_t)watchdog_get_drvdata(wdd), 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(wdd, SMCWD_PET, 0, NULL);
> +}
> +
> +static unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct arm_smccc_res res;
> +
> +	smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, &res);
> +	if (res.a0)
> +		return 0;
> +	return res.a1;
> +}
> +
> +static int smcwd_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
> +{
> +	int res;
> +
> +	res = smcwd_call(wdd, SMCWD_SET_TIMEOUT, timeout, NULL);
> +	if (!res)
> +		wdd->timeout = timeout;
> +	return res;
> +}
> +
> +static int smcwd_stop(struct watchdog_device *wdd)
> +{
> +	return smcwd_call(wdd, SMCWD_ENABLE, 0, NULL);
> +}
> +
> +static int smcwd_start(struct watchdog_device *wdd)
> +{
> +	return smcwd_call(wdd, 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;
> +	u32 smc_func_id;
> +
> +	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
> +	if (!wdd)
> +		return -ENOMEM;
> +	platform_set_drvdata(pdev, wdd);
> +
> +	if (of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
> +				 &smc_func_id))
> +		smc_func_id = 0x82003D06;
> +	watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);
> +
> +	err = smcwd_call(wdd, SMCWD_INIT, 0, &res);
> +	if (err < 0)
> +		return err;
> +
> +	wdd->info = &smcwd_info;
> +	/* get_timeleft is optional */
> +	if (smcwd_call(wdd, 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 = "arm,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);
>