Date:	Thu, 11 Jun 2015 09:28:10 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	fu.wei@...aro.org
Cc:	Suravee.Suthikulpanit@....com, linaro-acpi@...ts.linaro.org,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	tekkamanninja@...il.com, graeme.gregory@...aro.org,
	al.stone@...aro.org, hanjun.guo@...aro.org, timur@...eaurora.org,
	ashwin.chaugule@...aro.org, arnd@...db.de, vgandhi@...eaurora.org,
	wim@...ana.be, jcm@...hat.com, leo.duran@....com, corbet@....net,
	mark.rutland@....com, catalin.marinas@....com, will.deacon@....com,
	rjw@...ysocki.net
Subject: Re: [non-pretimeout,4/7] Watchdog: introduce ARM SBSA watchdog driver

On Thu, Jun 11, 2015 at 01:47:29AM +0800, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
> 
> This driver bases on linux kernel watchdog framework.
> It supports getting timeout from parameter and FDT
> at the driver init stage.
> The first timeout period expires, the interrupt routine
> got another timeout period to run panic for saving
> system context.
> 
Comments inline.

Thanks,
Guenter

> Signed-off-by: Fu Wei <fu.wei@...aro.org>
> ---
>  drivers/watchdog/Kconfig     |  11 ++
>  drivers/watchdog/Makefile    |   1 +
>  drivers/watchdog/sbsa_gwdt.c | 383 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 395 insertions(+)
>  create mode 100644 drivers/watchdog/sbsa_gwdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index e5e7c55..554f18a 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -152,6 +152,17 @@ config ARM_SP805_WATCHDOG
>  	  ARM Primecell SP805 Watchdog timer. This will reboot your system when
>  	  the timeout is reached.
>  
> +config ARM_SBSA_WATCHDOG
> +	tristate "ARM SBSA Generic Watchdog"
> +	depends on ARM64
> +	depends on ARM_ARCH_TIMER
> +	select WATCHDOG_CORE
> +	help
> +	  ARM SBSA Generic Watchdog. This watchdog has two Watchdog timeouts.
> +	  The first timeout will trigger a panic; the second timeout will
> +	  trigger a system reset.
> +	  More details: ARM DEN0029B - Server Base System Architecture (SBSA)
> +
	  To compile this driver as module, choose M here: The module
	  will be called sbsa_gwdt.

>  config AT91RM9200_WATCHDOG
>  	tristate "AT91RM9200 watchdog"
>  	depends on SOC_AT91RM9200 && MFD_SYSCON
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 5c19294..471f1b7c 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -30,6 +30,7 @@ obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
>  
>  # ARM Architecture
>  obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
> +obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
>  obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
>  obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o
>  obj-$(CONFIG_CADENCE_WATCHDOG) += cadence_wdt.o
> diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
> new file mode 100644
> index 0000000..1ddc10f
> --- /dev/null
> +++ b/drivers/watchdog/sbsa_gwdt.c
> @@ -0,0 +1,383 @@
> +/*
> + * SBSA(Server Base System Architecture) Generic Watchdog driver
> + *
> + * Copyright (c) 2015, Linaro Ltd.
> + * Author: Fu Wei <fu.wei@...aro.org>
> + *         Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License 2 as published
> + * by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * Note: This SBSA Generic watchdog has two stage timeouts,

s/This/The/

"has two stages".

I would suggest to drop "Note:", but that is up to you.

> + *       When the first timeout occurs, WS0(SPI or LPI) is triggered,
> + *       the second timeout period(as long as the first timeout period) starts.

no longer accurate if WOR is used for the second period.

> + *       In WS0 interrupt routine, panic() will be called for collecting
> + *       crashdown info.
> + *       If system can not recover from WS0 interrupt routine, then second
> + *       timeout occurs, WS1(reset or higher level interrupt) is triggered.
> + *       The two timeout period can be set by WOR(32bit).

The second timeout period is determined by ...

> + *       WOR gives a maximum watch period of around 10s at the maximum
> + *       system counter frequency.
> + *       The System Counter shall run at maximum of 400MHz.

"... at the maximum system counter frequency of 400 MHz.", and drop the
last sentence.

Please uses spaces before '('.

> + *
> + *       But If we need a larger timeout period, this driver will programme WCV

s/But //
s/this/the/
s/programme/program/

> + *       directly. That can support more than 10s timeout at the maximum
> + *       system counter frequency.

Drop the last sentence.

> + *       More details: ARM DEN0029B - Server Base System Architecture (SBSA)
> + *
> + * SBSA GWDT:    |---WOR(or WCV)---WS0---WOR(or WCV)---WS1
> + *               |-----timeout-----WS0-----timeout-----WS1
> + */
> +
> +#include <linux/io.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +#include <linux/watchdog.h>
> +#include <asm/arch_timer.h>
> +
> +/* SBSA Generic Watchdog register definitions */
> +/* refresh frame */
> +#define SBSA_GWDT_WRR				0x000
> +
> +/* control frame */
> +#define SBSA_GWDT_WCS				0x000
> +#define SBSA_GWDT_WOR				0x008
> +#define SBSA_GWDT_WCV_LO			0x010
> +#define SBSA_GWDT_WCV_HI			0x014
> +
> +/* refresh/control frame */
> +#define SBSA_GWDT_W_IIDR			0xfcc
> +#define SBSA_GWDT_IDR				0xfd0
> +
> +/* Watchdog Control and Status Register */
> +#define SBSA_GWDT_WCS_EN			BIT(0)
> +#define SBSA_GWDT_WCS_WS0			BIT(1)
> +#define SBSA_GWDT_WCS_WS1			BIT(2)
> +
> +/**
> + * struct sbsa_gwdt - Internal representation of the SBSA GWDT
> + * @wdd:		kernel watchdog_device structure
> + * @clk:		store the System Counter clock frequency, in Hz.
> + * @max_wor_timeout:	the maximum timeout value for WOR (in seconds).
> + * @refresh_base:	Virtual address of the watchdog refresh frame
> + * @control_base:	Virtual address of the watchdog control frame
> + */
> +struct sbsa_gwdt {
> +	struct watchdog_device	wdd;
> +	u32			clk;
> +	int			max_wor_timeout;
> +	void __iomem		*refresh_base;
> +	void __iomem		*control_base;
> +};
> +
> +#define to_sbsa_gwdt(e) container_of(e, struct sbsa_gwdt, wdd)
> +
> +#define DEFAULT_TIMEOUT		30 /* seconds */
> +
> +static unsigned int timeout;
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout,
> +		 "Watchdog timeout in seconds. (>=0, default="
> +		 __MODULE_STRING(DEFAULT_TIMEOUT) ")");
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, S_IRUGO);
> +MODULE_PARM_DESC(nowayout,
> +		 "Watchdog cannot be stopped once started (default="
> +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +/*
> + * help functions for accessing 64bit WCV register
> + */
> +static u64 sbsa_gwdt_get_wcv(struct watchdog_device *wdd)
> +{
> +	u32 wcv_lo, wcv_hi;
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +	do {
> +		wcv_hi = readl_relaxed(gwdt->control_base + SBSA_GWDT_WCV_HI);
> +		wcv_lo = readl_relaxed(gwdt->control_base + SBSA_GWDT_WCV_LO);
> +	} while (wcv_hi != readl_relaxed(gwdt->control_base +
> +					 SBSA_GWDT_WCV_HI));
> +
> +	return (((u64)wcv_hi << 32) | wcv_lo);
> +}
> +
> +static void reload_timeout_to_wcv(struct watchdog_device *wdd)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +	u64 wcv;
> +
> +	wcv = arch_counter_get_cntvct() + (u64)wdd->timeout * gwdt->clk;
> +
> +	writel_relaxed(upper_32_bits(wcv),
> +		       gwdt->control_base + SBSA_GWDT_WCV_HI);
> +	writel_relaxed(lower_32_bits(wcv),
> +		       gwdt->control_base + SBSA_GWDT_WCV_LO);
> +}
> +
> +static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
> +				 unsigned int timeout)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +	wdd->timeout = timeout;
> +
> +	if (timeout <= gwdt->max_wor_timeout)
> +		writel_relaxed(timeout * gwdt->clk,
> +			       gwdt->control_base + SBSA_GWDT_WOR);
> +	else
> +		writel_relaxed(gwdt->max_wor_timeout * gwdt->clk,
> +			       gwdt->control_base + SBSA_GWDT_WOR);
> +

This can be simplified a bit to
	if (timeout > gwdt->max_wor_timeout)
		timeout = gwdt->max_wor_timeout;
	writel_relaxed(timeout * gwdt->clk,
		       gwdt->control_base + SBSA_GWDT_WOR);

> +	return 0;
> +}
> +
> +static unsigned int sbsa_gwdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +	u64 timeleft = sbsa_gwdt_get_wcv(wdd) - arch_counter_get_cntvct();
> +
> +	do_div(timeleft, gwdt->clk);
> +
> +	return timeleft;
> +}
> +
> +static int sbsa_gwdt_keepalive(struct watchdog_device *wdd)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +	if (wdd->timeout <= gwdt->max_wor_timeout)
> +		/*
> +		 * Writing WRR for an explicit watchdog refresh.
> +		 * You can write anyting(like 0xc0ffee).
> +		 */
> +		writel_relaxed(0xc0ffee, gwdt->refresh_base + SBSA_GWDT_WRR);
> +	else
> +		reload_timeout_to_wcv(wdd);
> +
> +	return 0;
> +}
> +
> +static int sbsa_gwdt_start(struct watchdog_device *wdd)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +	/* Force refresh due to hardware bug found in certain Soc. */

Can you specify which SOC(s) are known to need this, and explain the bug
a bit better ?

> +	writel_relaxed(0xc0ffee, gwdt->refresh_base + SBSA_GWDT_WRR);
> +	/* writing WCS will cause an explicit watchdog refresh */
> +	writel_relaxed(SBSA_GWDT_WCS_EN, gwdt->control_base + SBSA_GWDT_WCS);
> +
> +	return sbsa_gwdt_keepalive(wdd);
> +}
> +
> +static int sbsa_gwdt_stop(struct watchdog_device *wdd)
> +{
> +	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +	writel_relaxed(0, gwdt->control_base + SBSA_GWDT_WCS);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id)
> +{
> +	struct sbsa_gwdt *gwdt = (struct sbsa_gwdt *)dev_id;
> +	struct watchdog_device *wdd = &gwdt->wdd;
> +
> +	if (wdd->timeout > gwdt->max_wor_timeout)
> +		reload_timeout_to_wcv(wdd);
> +
Please drop the above.

> +	panic("SBSA Watchdog pre-timeout");
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static struct watchdog_info sbsa_gwdt_info = {
> +	.identity	= "SBSA Generic Watchdog",
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE |
> +			  WDIOF_CARDRESET,
> +};
> +
> +static struct watchdog_ops sbsa_gwdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= sbsa_gwdt_start,
> +	.stop		= sbsa_gwdt_stop,
> +	.ping		= sbsa_gwdt_keepalive,
> +	.set_timeout	= sbsa_gwdt_set_timeout,
> +	.get_timeleft	= sbsa_gwdt_get_timeleft,
> +};
> +
> +static int sbsa_gwdt_probe(struct platform_device *pdev)
> +{
> +	u64 first_period_max = U64_MAX;
> +	struct device *dev = &pdev->dev;
> +	struct watchdog_device *wdd;
> +	struct sbsa_gwdt *gwdt;
> +	struct resource *res;
> +	void *rf_base, *cf_base;
> +	int ret, irq;
> +	u32 status;
> +
> +	gwdt = devm_kzalloc(dev, sizeof(*gwdt), GFP_KERNEL);
> +	if (!gwdt)
> +		return -ENOMEM;
> +	platform_set_drvdata(pdev, gwdt);
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "refresh");
> +	rf_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(rf_base))
> +		return PTR_ERR(rf_base);
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "control");
> +	cf_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(cf_base))
> +		return PTR_ERR(cf_base);
> +
> +	irq = platform_get_irq_byname(pdev, "ws0");
> +	if (irq < 0) {
> +		dev_err(dev, "unable to get ws0 interrupt.\n");
> +		return irq;
> +	}
> +
> +	/*
> +	 * Get the frequency of system counter from the cp15 interface of ARM
> +	 * Generic timer. We don't need to check it, because if it returns "0",
> +	 * system would panic in very early stage.
> +	 */
> +	gwdt->clk = arch_timer_get_cntfrq();
> +	gwdt->refresh_base = rf_base;
> +	gwdt->control_base = cf_base;
> +	gwdt->max_wor_timeout = U32_MAX / gwdt->clk;
> +
> +	wdd = &gwdt->wdd;
> +	wdd->parent = dev;
> +	wdd->info = &sbsa_gwdt_info;
> +	wdd->ops = &sbsa_gwdt_ops;
> +	watchdog_set_drvdata(wdd, gwdt);
> +	watchdog_set_nowayout(wdd, nowayout);
> +
> +	wdd->min_timeout = 1;
> +	do_div(first_period_max, gwdt->clk);
> +	wdd->max_timeout = first_period_max;
> +
> +	wdd->timeout = DEFAULT_TIMEOUT;
> +	watchdog_init_timeout(wdd, timeout, dev);
> +
> +	status = readl_relaxed(gwdt->control_base + SBSA_GWDT_WCS);
> +	if (status & SBSA_GWDT_WCS_WS1) {
> +		dev_warn(dev, "System reset by WDT(WCV: %llx)\n",
> +			 sbsa_gwdt_get_wcv(wdd));

WCV here only tells us how many clock cycles were executed since the
system started (or something like that). So I still don't understand
why it is valuable to print that number.

> +		wdd->bootstatus |= WDIOF_CARDRESET;
> +	}
> +	/* Check if watchdog is already enabled */
> +	if (status & SBSA_GWDT_WCS_EN) {
> +		dev_warn(dev, "already enabled\n");
> +		sbsa_gwdt_keepalive(wdd);
> +	}

Can you merge the message with the info message below ?
Something like
	dev_info(dev, "Initialized with %ds timeout @ %u Hz%s\n", wdd->timeout,
		 gwdt->clk, status & SBSA_GWDT_WCS_EN ? " [enabled]" : "");

I don't think that should be a warning.

> +
> +	/* update timeout to WOR */
> +	sbsa_gwdt_set_timeout(wdd, wdd->timeout);
> +

That will trigger a refresh if the watchdog is active, meaning the timeout
will occur at time + WOR, not at time + timeout. I think keepalive has to be
called later, preferrably after calling watchdog_register_device().

> +	ret = devm_request_irq(dev, irq, sbsa_gwdt_interrupt, 0,
> +			       pdev->name, gwdt);
> +	if (ret) {
> +		dev_err(dev, "unable to request IRQ %d\n", irq);
> +		return ret;
> +	}
> +
> +	ret = watchdog_register_device(wdd);
> +	if (ret)
> +		return ret;
> +
> +	dev_info(dev, "Initialized with %ds timeout @ %u Hz\n", wdd->timeout,
> +		 gwdt->clk);
> +
> +	return 0;
> +}
> +
> +static void sbsa_gwdt_shutdown(struct platform_device *pdev)
> +{
> +	struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
> +
> +	sbsa_gwdt_stop(&gwdt->wdd);
> +}
> +
> +static int sbsa_gwdt_remove(struct platform_device *pdev)
> +{
> +	struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
> +
> +	watchdog_unregister_device(&gwdt->wdd);
> +
> +	return 0;
> +}
> +
> +/* Disable watchdog if it is active during suspend */
> +static int __maybe_unused sbsa_gwdt_suspend(struct device *dev)
> +{
> +	struct sbsa_gwdt *gwdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&gwdt->wdd))
> +		sbsa_gwdt_stop(&gwdt->wdd);
> +
> +	return 0;
> +}
> +
> +/* Enable watchdog and configure it if necessary */
> +static int __maybe_unused sbsa_gwdt_resume(struct device *dev)
> +{
> +	struct sbsa_gwdt *gwdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&gwdt->wdd))
> +		sbsa_gwdt_start(&gwdt->wdd);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops sbsa_gwdt_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(sbsa_gwdt_suspend, sbsa_gwdt_resume)
> +};
> +
> +static const struct of_device_id sbsa_gwdt_of_match[] = {
> +	{ .compatible = "arm,sbsa-gwdt", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, sbsa_gwdt_of_match);
> +
> +static const struct platform_device_id sbsa_gwdt_pdev_match[] = {
> +	{ .name = "sbsa-gwdt", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(platform, sbsa_gwdt_pdev_match);
> +
> +static struct platform_driver sbsa_gwdt_driver = {
> +	.driver = {
> +		.name = "sbsa-gwdt",
> +		.pm = &sbsa_gwdt_pm_ops,
> +		.of_match_table = sbsa_gwdt_of_match,
> +	},
> +	.probe = sbsa_gwdt_probe,
> +	.remove = sbsa_gwdt_remove,
> +	.shutdown = sbsa_gwdt_shutdown,
> +	.id_table = sbsa_gwdt_pdev_match,
> +};
> +
> +module_platform_driver(sbsa_gwdt_driver);
> +
> +MODULE_DESCRIPTION("SBSA Generic Watchdog Driver");
> +MODULE_VERSION("v1.0");

Version numbers tend to be out of date constantly, and there is no well
defined mechanism or protocol when increase them. I would suggest to drop it.

> +MODULE_AUTHOR("Fu Wei <fu.wei@...aro.org>");
> +MODULE_AUTHOR("Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>");
> +MODULE_LICENSE("GPL v2");
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