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Message-ID: <0af4aadc-a751-1179-61cc-b0253c71cf71@ti.com>
Date: Wed, 4 Mar 2020 12:44:55 +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 04/03/2020 11:23, Guenter Roeck wrote:
> On 3/3/20 10:57 PM, Tero Kristo wrote:
>> 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.
>>
>
> If it isn't needed to be held, you should use clk_get / clk_put,
> and not the devm_ functions.
Ok, changed this and posted v3 of patch #3 only.
-Tero
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