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Message-ID: <8cb36dce-bd2e-2581-5644-fc73e4d94316@roeck-us.net>
Date: Tue, 9 Jun 2020 06:42:49 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Dilip Kota <eswara.kota@...ux.intel.com>, wim@...ux-watchdog.org,
linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
robbh@...nel.org
Cc: linux-kernel@...r.kernel.org, andriy.shevchenko@...el.com,
cheol.yong.kim@...el.com, qi-ming.wu@...el.com, yixin.zhu@...el.com
Subject: Re: [PATCH 2/2] watchdog: intel: Watchdog timer support on Lightning
Mountain
On 6/9/20 1:57 AM, Dilip Kota wrote:
>
> On 6/8/2020 9:36 PM, Guenter Roeck wrote:
>> On 6/7/20 10:49 PM, Dilip Kota wrote:
>>> On Intel Lightning Mountain SoC, General Purpose Timer Counter(GPTC)
>>> programmable as clocksource, real time clock or watchdog timer.
>>>
>>> This driver configures GPTC as Watchdog timer and triggers reset signal
>>> to CPU on timeout.
>>>
>>> Signed-off-by: Dilip Kota <eswara.kota@...ux.intel.com>
>>> ---
>>> drivers/watchdog/Kconfig | 13 ++
>>> drivers/watchdog/Makefile | 1 +
>>> drivers/watchdog/intel_lgm_gptc_wdt.c | 420 ++++++++++++++++++++++++++++++++++
>>> 3 files changed, 434 insertions(+)
>>> create mode 100644 drivers/watchdog/intel_lgm_gptc_wdt.c
>>>
>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>> index 0663c604bd642..8009c11e75dda 100644
>>> --- a/drivers/watchdog/Kconfig
>>> +++ b/drivers/watchdog/Kconfig
>>> @@ -1789,6 +1789,19 @@ config IMGPDC_WDT
>>> To compile this driver as a loadable module, choose M here.
>>> The module will be called imgpdc_wdt.
>>> +config INTEL_LGM_GPTC_WDT
>>> + tristate "INTEL LGM SoC Watchdog"
>>> + depends on X86 || COMPILE_TEST
>>> + depends on OF && HAS_IOMEM
>>> + select REGMAP
>>> + select MFD_SYSCON
>>> + select WATCHDOG_CORE
>>> + help
>>> + Driver for Watchdog Timer on Intel Lightning Mountain SoC.
>>> +
>>> + To compile this driver as a loadable module, choose M here.
>>> + The module will be called intel_lgm_gptc_wdt.
>>> +
>>> config LANTIQ_WDT
>>> tristate "Lantiq SoC watchdog"
>>> depends on LANTIQ
>>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
>>> index 6de2e4ceef190..92c99e4c46eb7 100644
>>> --- a/drivers/watchdog/Makefile
>>> +++ b/drivers/watchdog/Makefile
>>> @@ -166,6 +166,7 @@ obj-$(CONFIG_TXX9_WDT) += txx9wdt.o
>>> obj-$(CONFIG_OCTEON_WDT) += octeon-wdt.o
>>> octeon-wdt-y := octeon-wdt-main.o octeon-wdt-nmi.o
>>> obj-$(CONFIG_LANTIQ_WDT) += lantiq_wdt.o
>>> +obj-$(CONFIG_INTEL_LGM_GPTC_WDT) += intel_lgm_gptc_wdt.o
>>> obj-$(CONFIG_LOONGSON1_WDT) += loongson1_wdt.o
>>> obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
>>> obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
>>> diff --git a/drivers/watchdog/intel_lgm_gptc_wdt.c b/drivers/watchdog/intel_lgm_gptc_wdt.c
>>> new file mode 100644
>>> index 0000000000000..52be7cc194f8f
>>> --- /dev/null
>>> +++ b/drivers/watchdog/intel_lgm_gptc_wdt.c
>>> @@ -0,0 +1,420 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright (C) 2020 Intel Corporation.
>>> + */
>>> +
>>> +#include <linux/bitfield.h>
>>> +#include <linux/clk.h>
>>> +#include <linux/cpu.h>
>>> +#include <linux/io.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/mfd/syscon.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/regmap.h>
>>> +#include <linux/watchdog.h>
>>> +
>>> +#define GPTC_CLC 0x00
>>> +#define GPTC_CLC_SUSPEND BIT(4)
>>> +#define GPTC_CLC_RMC GENMASK(15, 8)
>>> +
>>> +/* divider 10 to produce 200 / 10 = 20 MHz clock */
>>> +#define CLC_RMC_DIV 10
>>> +
>>> +#define GPTC_CON(X) (0x10 + (X) * 0x20)
>>> +#define GPTC_CON_CNT_UP BIT(1)
>>> +#define GPTC_CON_ONESHOT BIT(3)
>>> +#define GPTC_CON_EXT BIT(4)
>>> +
>>> +#define GPTC_RUN(X) (0x18 + (X) * 0x20)
>>> +#define GPTC_RUN_EN BIT(0)
>>> +#define GPTC_RUN_STOP BIT(1)
>>> +#define GPTC_RUN_RELOAD BIT(2)
>>> +
>>> +#define GPTC_RLD(X) (0x20 + (X) * 0x20)
>>> +#define GPTC_CNT(X) (0x28 + (X) * 0x20)
>>> +
>>> +#define GPTC_IRNENCLR 0xF0
>>> +#define GPTC_IRNEN 0xF4
>>> +#define GPTC_IRNCR 0xFC
>>> +
>>> +/* Watchdog Timeout Reset register offset and bitfeilds */
>>> +#define BIA_WDT_RST_EN 0x1E0
>>> +#define BIA_WDT BIT(6)
>>> +
>>> +#define MAX_TIMERID 2
>>> +#define MAX_CPUID 3
>>> +#define TIMER_MARGIN_SEC 300
>>> +
>>> +static bool nowayout = WATCHDOG_NOWAYOUT;
>>> +module_param(nowayout, bool, 0);
>>> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started\n"
>>> + " (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>>> +
>>> +struct lgm_gptc_timer {
>>> + struct lgm_gptc_wdt *wdt_node;
>>> + struct watchdog_device wdd;
>>> + unsigned int tid;
>>> + unsigned int cpuid;
>>> + unsigned int frequency;
>>> + unsigned int cycles;
>>> + bool enable;
>>> +};
>>> +
>>> +struct lgm_gptc_wdt {
>>> + struct device *dev;
>>> + void __iomem *gptc_base;
>>> + struct regmap *rst_hndl;
>>> + struct clk *freqclk;
>>> + struct clk *gateclk;
>>> + unsigned int fpifreq;
>>> + enum cpuhp_state state;
>>> +};
>>> +
>>> +DEFINE_PER_CPU(struct lgm_gptc_timer, lgm_timer_per_cpu);
>>> +
>> This is unusual. You'll have to provide a very detailed explanation
>> why this is needed.
> Sure will add it.
> It is required for the hotplug cpu support, and hotplug cpu is added because, the cpus on Lightning Mountain SoC can be online and offline dynamically.
> If CPUs come to online after the watchdog driver probe, hotplug CPU support helps to configure watchdog timer once CPU is online.
>
There is another watchdog in the system monitoring individual CPUs.
The watchdog subsystem monitors the system, not individual CPUs.
Individual CUPs are monitored with kernel/watchdog.c, and we should
keep it that way.
Guenter
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