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Date:   Wed, 4 Mar 2020 14:06:48 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Tero Kristo <t-kristo@ti.com>
Cc:     wim@linux-watchdog.org, linux-watchdog@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3 3/4] watchdog: Add K3 RTI watchdog support
Message-ID: <20200304220648.GA31640@roeck-us.net>
References: <aed89814-a78b-4a59-7673-bce5de34022d@roeck-us.net>
 <20200304104214.8625-1-t-kristo@ti.com>
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On Wed, Mar 04, 2020 at 12:42:14PM +0200, Tero Kristo wrote:
> Texas Instruments K3 SoCs contain an RTI (Real Time Interrupt) module
> which can be used as a watchdog. This IP provides a support for
> windowed watchdog mode, in which the watchdog must be petted within
> a certain time window. If it is petted either too soon, or too late,
> a watchdog error will be triggered.
> 
> Signed-off-by: Tero Kristo <t-kristo@ti.com>

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

> ---
> v3:
>   * changed to use clk_get/put instead of devm_* versions of this
> 
> v2:
>   * Added better documentation within the driver code
>   * Dropped fck handle, instead get the fck rate during probe only
>   * Modified the max_hw_heartbeat calculation logic a bit
> 
>  drivers/watchdog/Kconfig   |   8 ++
>  drivers/watchdog/Makefile  |   1 +
>  drivers/watchdog/rti_wdt.c | 255 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 261 insertions(+)
>  create mode 100644 drivers/watchdog/rti_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index cec868f8db3f..81faf47d44a6 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -583,6 +583,14 @@ config DAVINCI_WATCHDOG
>  	  NOTE: once enabled, this timer cannot be disabled.
>  	  Say N if you are unsure.
>  
> +config K3_RTI_WATCHDOG
> +	tristate "Texas Instruments K3 RTI watchdog"
> +	depends on ARCH_K3 || COMPILE_TEST
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here if you want to include support for the K3 watchdog
> +	  timer (RTI module) available in the K3 generation of processors.
> +
>  config ORION_WATCHDOG
>  	tristate "Orion watchdog"
>  	depends on ARCH_ORION5X || ARCH_DOVE || MACH_DOVE || ARCH_MVEBU || (COMPILE_TEST && !ARCH_EBSA110)
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 2ee352bf3372..6de2e4ceef19 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -57,6 +57,7 @@ obj-$(CONFIG_EP93XX_WATCHDOG) += ep93xx_wdt.o
>  obj-$(CONFIG_PNX4008_WATCHDOG) += pnx4008_wdt.o
>  obj-$(CONFIG_IOP_WATCHDOG) += iop_wdt.o
>  obj-$(CONFIG_DAVINCI_WATCHDOG) += davinci_wdt.o
> +obj-$(CONFIG_K3_RTI_WATCHDOG) += rti_wdt.o
>  obj-$(CONFIG_ORION_WATCHDOG) += orion_wdt.o
>  obj-$(CONFIG_SUNXI_WATCHDOG) += sunxi_wdt.o
>  obj-$(CONFIG_RN5T618_WATCHDOG) += rn5t618_wdt.o
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> new file mode 100644
> index 000000000000..7a46c40891e2
> --- /dev/null
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -0,0 +1,255 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Watchdog driver for the K3 RTI module
> + *
> + * (c) Copyright 2019-2020 Texas Instruments Inc.
> + * All rights reserved.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/types.h>
> +#include <linux/watchdog.h>
> +
> +#define DEFAULT_HEARTBEAT 60
> +
> +/* Max heartbeat is calculated at 32kHz source clock */
> +#define MAX_HEARTBEAT	1000
> +
> +/* Timer register set definition */
> +#define RTIDWDCTRL	0x90
> +#define RTIDWDPRLD	0x94
> +#define RTIWDSTATUS	0x98
> +#define RTIWDKEY	0x9c
> +#define RTIDWDCNTR	0xa0
> +#define RTIWWDRXCTRL	0xa4
> +#define RTIWWDSIZECTRL	0xa8
> +
> +#define RTIWWDRX_NMI	0xa
> +
> +#define RTIWWDSIZE_50P	0x50
> +
> +#define WDENABLE_KEY	0xa98559da
> +
> +#define WDKEY_SEQ0		0xe51a
> +#define WDKEY_SEQ1		0xa35c
> +
> +#define WDT_PRELOAD_SHIFT	13
> +
> +#define WDT_PRELOAD_MAX		0xfff
> +
> +#define DWDST			BIT(1)
> +
> +static int heartbeat;
> +
> +/*
> + * struct to hold data for each WDT device
> + * @base - base io address of WD device
> + * @freq - source clock frequency of WDT
> + * @wdd  - hold watchdog device as is in WDT core
> + */
> +struct rti_wdt_device {
> +	void __iomem		*base;
> +	unsigned long		freq;
> +	struct watchdog_device	wdd;
> +};
> +
> +static int rti_wdt_start(struct watchdog_device *wdd)
> +{
> +	u32 timer_margin;
> +	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
> +
> +	/* set timeout period */
> +	timer_margin = (u64)wdd->timeout * wdt->freq;
> +	timer_margin >>= WDT_PRELOAD_SHIFT;
> +	if (timer_margin > WDT_PRELOAD_MAX)
> +		timer_margin = WDT_PRELOAD_MAX;
> +	writel_relaxed(timer_margin, wdt->base + RTIDWDPRLD);
> +
> +	/*
> +	 * RTI only supports a windowed mode, where the watchdog can only
> +	 * be petted during the open window; not too early or not too late.
> +	 * The HW configuration options only allow for the open window size
> +	 * to be 50% or less than that; we obviouly want to configure the open
> +	 * window as large as possible so we select the 50% option. To avoid
> +	 * any glitches, we accommodate 5% safety margin also, so we setup
> +	 * the min_hw_hearbeat at 55% of the timeout period.
> +	 */
> +	wdd->min_hw_heartbeat_ms = 11 * wdd->timeout * 1000 / 20;
> +
> +	/* Generate NMI when wdt expires */
> +	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
> +
> +	/* Open window size 50%; this is the largest window size available */
> +	writel_relaxed(RTIWWDSIZE_50P, wdt->base + RTIWWDSIZECTRL);
> +
> +	readl_relaxed(wdt->base + RTIWWDSIZECTRL);
> +
> +	/* enable watchdog */
> +	writel_relaxed(WDENABLE_KEY, wdt->base + RTIDWDCTRL);
> +	return 0;
> +}
> +
> +static int rti_wdt_ping(struct watchdog_device *wdd)
> +{
> +	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
> +
> +	/* put watchdog in service state */
> +	writel_relaxed(WDKEY_SEQ0, wdt->base + RTIWDKEY);
> +	/* put watchdog in active state */
> +	writel_relaxed(WDKEY_SEQ1, wdt->base + RTIWDKEY);
> +
> +	return 0;
> +}
> +
> +static unsigned int rti_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	u64 timer_counter;
> +	u32 val;
> +	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
> +
> +	/* if timeout has occurred then return 0 */
> +	val = readl_relaxed(wdt->base + RTIWDSTATUS);
> +	if (val & DWDST)
> +		return 0;
> +
> +	timer_counter = readl_relaxed(wdt->base + RTIDWDCNTR);
> +
> +	do_div(timer_counter, wdt->freq);
> +
> +	return timer_counter;
> +}
> +
> +static const struct watchdog_info rti_wdt_info = {
> +	.options = WDIOF_KEEPALIVEPING,
> +	.identity = "K3 RTI Watchdog",
> +};
> +
> +static const struct watchdog_ops rti_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= rti_wdt_start,
> +	.ping		= rti_wdt_ping,
> +	.get_timeleft	= rti_wdt_get_timeleft,
> +};
> +
> +static int rti_wdt_probe(struct platform_device *pdev)
> +{
> +	int ret = 0;
> +	struct device *dev = &pdev->dev;
> +	struct resource *wdt_mem;
> +	struct watchdog_device *wdd;
> +	struct rti_wdt_device *wdt;
> +	struct clk *clk;
> +
> +	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	clk = clk_get(dev, NULL);
> +	if (IS_ERR(clk)) {
> +		if (PTR_ERR(clk) != -EPROBE_DEFER)
> +			dev_err(dev, "failed to get clock\n");
> +		return PTR_ERR(clk);
> +	}
> +
> +	wdt->freq = clk_get_rate(clk);
> +
> +	clk_put(clk);
> +
> +	if (!wdt->freq) {
> +		dev_err(dev, "Failed to get fck rate.\n");
> +		return -EINVAL;
> +	}
> +
> +	pm_runtime_enable(dev);
> +	ret = pm_runtime_get_sync(dev);
> +	if (ret) {
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "runtime pm failed\n");
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, wdt);
> +
> +	wdd = &wdt->wdd;
> +	wdd->info = &rti_wdt_info;
> +	wdd->ops = &rti_wdt_ops;
> +	wdd->min_timeout = 1;
> +	wdd->max_hw_heartbeat_ms = (WDT_PRELOAD_MAX << WDT_PRELOAD_SHIFT) /
> +		wdt->freq * 1000;
> +	wdd->timeout = DEFAULT_HEARTBEAT;
> +	wdd->parent = dev;
> +
> +	watchdog_init_timeout(wdd, heartbeat, dev);
> +
> +	watchdog_set_drvdata(wdd, wdt);
> +	watchdog_set_nowayout(wdd, 1);
> +	watchdog_set_restart_priority(wdd, 128);
> +
> +	wdt_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	wdt->base = devm_ioremap_resource(dev, wdt_mem);
> +	if (IS_ERR(wdt->base)) {
> +		ret = PTR_ERR(wdt->base);
> +		goto err_iomap;
> +	}
> +
> +	ret = watchdog_register_device(wdd);
> +	if (ret) {
> +		dev_err(dev, "cannot register watchdog device\n");
> +		goto err_iomap;
> +	}
> +
> +	return 0;
> +
> +err_iomap:
> +	pm_runtime_put_sync(&pdev->dev);
> +
> +	return ret;
> +}
> +
> +static int rti_wdt_remove(struct platform_device *pdev)
> +{
> +	struct rti_wdt_device *wdt = platform_get_drvdata(pdev);
> +
> +	watchdog_unregister_device(&wdt->wdd);
> +	pm_runtime_put(&pdev->dev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id rti_wdt_of_match[] = {
> +	{ .compatible = "ti,rti-wdt", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, rti_wdt_of_match);
> +
> +static struct platform_driver rti_wdt_driver = {
> +	.driver = {
> +		.name = "rti-wdt",
> +		.of_match_table = rti_wdt_of_match,
> +	},
> +	.probe = rti_wdt_probe,
> +	.remove = rti_wdt_remove,
> +};
> +
> +module_platform_driver(rti_wdt_driver);
> +
> +MODULE_AUTHOR("Tero Kristo <t-kristo@ti.com>");
> +MODULE_DESCRIPTION("K3 RTI Watchdog Driver");
> +
> +module_param(heartbeat, int, 0);
> +MODULE_PARM_DESC(heartbeat,
> +		 "Watchdog heartbeat period in seconds from 1 to "
> +		 __MODULE_STRING(MAX_HEARTBEAT) ", default "
> +		 __MODULE_STRING(DEFAULT_HEARTBEAT));
> +
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:rti-wdt");
> -- 
> 2.17.1
> 
> --
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki