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Date:   Tue, 26 Feb 2019 14:38:46 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Anson Huang <anson.huang@nxp.com>
Cc:     "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
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        "will.deacon@arm.com" <will.deacon@arm.com>,
        "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        Aisheng Dong <aisheng.dong@nxp.com>,
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        Daniel Baluta <daniel.baluta@nxp.com>,
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        <linux-arm-kernel@lists.infradead.org>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH V3 2/4] watchdog: imx_sc: Add i.MX system controller
 watchdog support
Message-ID: <20190226223846.GB30985@roeck-us.net>
References: <1551060850-22553-1-git-send-email-Anson.Huang@nxp.com>
 <1551060850-22553-3-git-send-email-Anson.Huang@nxp.com>
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On Mon, Feb 25, 2019 at 02:19:10AM +0000, Anson Huang wrote:
> i.MX8QXP is an ARMv8 SoC which has a Cortex-M4 system controller
> inside, the system controller is in charge of controlling power,
> clock and watchdog etc..
> 
> This patch adds i.MX system controller watchdog driver support,
> watchdog operation needs to be done in secure EL3 mode via
> ARM-Trusted-Firmware, using SMC call, CPU will trap into
> ARM-Trusted-Firmware and then it will request system controller
> to do watchdog operation via IPC.
> 
> Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> ---
> Changes since V2:
> 	- improve watchdog_init_timeout() operation and error check, setting it
> 	  via module parameter "timeout", if it is invalid, roll back to use defaul
> 	  timeout value DEFAULT_TIMEOUT;
> 	- change compatible string to "fsl,imx-sc-wdt" to make driver more generic
> 	  for all i.MX platforms with system controller watchdog inside.
> ---
>  drivers/watchdog/Kconfig      |  13 +++
>  drivers/watchdog/Makefile     |   1 +
>  drivers/watchdog/imx_sc_wdt.c | 183 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 197 insertions(+)
>  create mode 100644 drivers/watchdog/imx_sc_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 65c3c42..5c5b8ba 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -625,6 +625,19 @@ config IMX2_WDT
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called imx2_wdt.
>  
> +config IMX_SC_WDT
> +	tristate "IMX SC Watchdog"
> +	depends on ARCH_MXC || COMPILE_TEST

Wondering: Did you test on other architectures ? The code calls
arm_smccc_smc(), which is unlikely to be available on non-ARM
platforms, and I don't see a dummy declaration for those.

> +	select WATCHDOG_CORE
> +	help
> +	  This is the driver for the system controller watchdog
> +	  on the NXP i.MX SoCs with system controller inside.
> +	  If you have one of these processors and wish to have
> +	  watchdog support enabled, say Y, otherwise say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called imx_sc_wdt.
> +
>  config UX500_WATCHDOG
>  	tristate "ST-Ericsson Ux500 watchdog"
>  	depends on MFD_DB8500_PRCMU
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 4e78a8c..0c9da63 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -68,6 +68,7 @@ obj-$(CONFIG_NUC900_WATCHDOG) += nuc900_wdt.o
>  obj-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
>  obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
>  obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o
> +obj-$(CONFIG_IMX_SC_WDT) += imx_sc_wdt.o
>  obj-$(CONFIG_UX500_WATCHDOG) += ux500_wdt.o
>  obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
>  obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
> diff --git a/drivers/watchdog/imx_sc_wdt.c b/drivers/watchdog/imx_sc_wdt.c
> new file mode 100644
> index 0000000..7b22575
> --- /dev/null
> +++ b/drivers/watchdog/imx_sc_wdt.c
> @@ -0,0 +1,183 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2018-2019 NXP.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +#include <linux/watchdog.h>
> +
> +#define DEFAULT_TIMEOUT 60
> +/*
> + * Software timer tick implemented in scfw side, support 10ms to 0xffffffff ms
> + * in theory, but for normal case, 1s~128s is enough, you can change this max
> + * value in case it's not enough.
> + */
> +#define MAX_TIMEOUT 128
> +
> +#define IMX_SIP_TIMER			0xC2000002
> +#define IMX_SIP_TIMER_START_WDOG		0x01
> +#define IMX_SIP_TIMER_STOP_WDOG		0x02
> +#define IMX_SIP_TIMER_SET_WDOG_ACT	0x03
> +#define IMX_SIP_TIMER_PING_WDOG		0x04
> +#define IMX_SIP_TIMER_SET_TIMEOUT_WDOG	0x05
> +#define IMX_SIP_TIMER_GET_WDOG_STAT	0x06
> +#define IMX_SIP_TIMER_SET_PRETIME_WDOG	0x07
> +
> +#define SC_TIMER_WDOG_ACTION_PARTITION	0
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, 0000);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +static unsigned int timeout = DEFAULT_TIMEOUT;

I assume this means that you specifically do _not_ want to support
timeout configuration via devicetree (unless the user explicitly sets
the timeout to 0 here).

Not that it really matters, since it looks like Rob won't accept a
watchdog node anyway.

> +module_param(timeout, uint, 0000);
> +MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
> +		 __MODULE_STRING(DEFAULT_TIMEOUT) ")");
> +
> +static int imx_sc_wdt_ping(struct watchdog_device *wdog)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_PING_WDOG,
> +		      0, 0, 0, 0, 0, 0, &res);
> +
> +	return res.a0;

I didn't comment on this before, but I am wondering: Does the 
system controller code return Linux error codes ? Is this
documented somewhere ?

> +}
> +
> +static int imx_sc_wdt_start(struct watchdog_device *wdog)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_START_WDOG,
> +		      0, 0, 0, 0, 0, 0, &res);
> +	if (res.a0)
> +		return res.a0;
> +
> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_SET_WDOG_ACT,
> +		      SC_TIMER_WDOG_ACTION_PARTITION,
> +		      0, 0, 0, 0, 0, &res);
> +	return res.a0;
> +}
> +
> +static int imx_sc_wdt_stop(struct watchdog_device *wdog)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_STOP_WDOG,
> +		      0, 0, 0, 0, 0, 0, &res);
> +
> +	return res.a0;
> +}
> +
> +static int imx_sc_wdt_set_timeout(struct watchdog_device *wdog,
> +				unsigned int timeout)
> +{
> +	struct arm_smccc_res res;
> +
> +	wdog->timeout = timeout;
> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_SET_TIMEOUT_WDOG,
> +		      timeout * 1000, 0, 0, 0, 0, 0, &res);
> +
> +	return res.a0;
> +}
> +
> +static const struct watchdog_ops imx_sc_wdt_ops = {
> +	.owner = THIS_MODULE,
> +	.start = imx_sc_wdt_start,
> +	.stop  = imx_sc_wdt_stop,
> +	.ping  = imx_sc_wdt_ping,
> +	.set_timeout = imx_sc_wdt_set_timeout,
> +};
> +
> +static const struct watchdog_info imx_sc_wdt_info = {
> +	.identity	= "i.MX SC watchdog timer",
> +	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE | WDIOF_PRETIMEOUT,
> +};
> +
> +static int imx_sc_wdt_probe(struct platform_device *pdev)
> +{
> +	struct watchdog_device *imx_sc_wdd;
> +	int ret;
> +
> +	imx_sc_wdd = devm_kzalloc(&pdev->dev, sizeof(*imx_sc_wdd), GFP_KERNEL);
> +	if (!imx_sc_wdd)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, imx_sc_wdd);
> +
> +	imx_sc_wdd->info = &imx_sc_wdt_info;
> +	imx_sc_wdd->ops = &imx_sc_wdt_ops;
> +	imx_sc_wdd->min_timeout = 1;
> +	imx_sc_wdd->max_timeout = MAX_TIMEOUT;
> +	imx_sc_wdd->parent = &pdev->dev;
> +	imx_sc_wdd->timeout = DEFAULT_TIMEOUT;
> +
> +	ret = watchdog_init_timeout(imx_sc_wdd, timeout, &pdev->dev);
> +	if (ret)
> +		dev_warn(&pdev->dev, "Failed to set timeout value, using default\n");
> +
> +	watchdog_stop_on_reboot(imx_sc_wdd);
> +	watchdog_stop_on_unregister(imx_sc_wdd);
> +
> +	ret = devm_watchdog_register_device(&pdev->dev, imx_sc_wdd);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to register watchdog device\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id imx_sc_wdt_dt_ids[] = {
> +	{ .compatible = "fsl,imx-sc-wdt", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, imx_sc_wdt_dt_ids);

I assume this will be dropped and replaced with platform code,
per feedback from Rob.

> +
> +static int __maybe_unused imx_sc_wdt_suspend(struct device *dev)
> +{
> +	struct watchdog_device *imx_sc_wdd = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(imx_sc_wdd))
> +		imx_sc_wdt_stop(imx_sc_wdd);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused imx_sc_wdt_resume(struct device *dev)
> +{
> +	struct watchdog_device *imx_sc_wdd = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(imx_sc_wdd))
> +		imx_sc_wdt_start(imx_sc_wdd);
> +
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(imx_sc_wdt_pm_ops,
> +			 imx_sc_wdt_suspend, imx_sc_wdt_resume);
> +
> +static struct platform_driver imx_sc_wdt_driver = {
> +	.probe		= imx_sc_wdt_probe,
> +	.driver		= {
> +		.name	= "imx-sc-wdt",
> +		.of_match_table = imx_sc_wdt_dt_ids,
> +		.pm	= &imx_sc_wdt_pm_ops,
> +	},
> +};
> +
> +module_platform_driver(imx_sc_wdt_driver);
> +
> +MODULE_AUTHOR("Robin Gong <yibin.gong@nxp.com>");
> +MODULE_DESCRIPTION("NXP i.MX system controller watchdog driver");
> +MODULE_LICENSE("GPL v2");

The module license conflicts with the SPDX license which says 2.0+.