Message-ID: <f167de86-6c76-0e4e-6c61-6e7ca989101d@ti.com>
Date:   Wed, 4 Mar 2020 08:57:15 +0200
From:   Tero Kristo <t-kristo@...com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     <wim@...ux-watchdog.org>, <linux-watchdog@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 3/4] watchdog: Add K3 RTI watchdog support

On 03/03/2020 23:18, Guenter Roeck wrote:
> On Mon, Mar 02, 2020 at 10:04:25PM +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@...com>
>> ---
>> 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 | 254 +++++++++++++++++++++++++++++++++++++
>>   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 +1,254 @@
>> +// 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 = devm_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);
>> +	if (!wdt->freq) {
>> +		dev_err(dev, "Failed to get fck rate.\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	devm_clk_put(dev, clk);
>> +
> Are you sure about this ? Doesn't this mean that the clock may be stopped ?
> Normally the reason for using devm_ functions during probe is that release
> functions are called automatically when the device is removed. Calling
> the release function dorectly is unusual and most of the time wrong.

clk_get / clk_put does not enable / disable a clock by itself, this is 
just used to fetch a clock handle. But you are right, we are never 
calling clk_enable on it either, because at least the 32kHz clock we are 
interested in is of type always-on and can never be disabled.

I can keep the clock handle and call enable/disable on it in the 
probe/remove if you think that would be neater.

-Tero

> 
> Thanks,
> Guenter
> 
>> +	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@...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
>>
>> --

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