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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Mon, 2 May 2022 19:19:51 -0700
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To:     nick.hawkins@hpe.com, verdun@hpe.com, nick@hpe.com, joel@jms.id.au,
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Cc:     Wim Van Sebroeck <wim@linux-watchdog.org>,
        linux-watchdog@vger.kernel.org
References: <20220502204050.88316-1-nick.hawkins@hpe.com>
 <20220502204050.88316-3-nick.hawkins@hpe.com>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v6 3/8] watchdog: hpe-wdt: Introduce HPE GXP Watchdog
In-Reply-To: <20220502204050.88316-3-nick.hawkins@hpe.com>
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On 5/2/22 13:40, nick.hawkins@hpe.com wrote:
> From: Nick Hawkins <nick.hawkins@hpe.com>
> 
> Adding support for the HPE GXP Watchdog. The GXP asic contains a full

Add

> compliment of timers one of which is the watchdog timer. The watchdog

complement ?

> timer is 16 bit and has 10ms resolution. The watchdog is created as a
> child device of timer since the same register range is used.
> 
> Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>
> 
> ---
> v6:
> * No code change.
> * Fixed commit subject line to match the ones in log.
> * Adjusted commit message to be closer to 75 chars per line.
> v5:
> * Fixed version log
> * Added details to Kconfig for module support.
> * Adjusted commit messaged
> v4:
> * Made watchdog a child of timer as they share the same register region
>    per change request on dtsi.
> * Removed extra parenthesis
> * Fixed u8 u32 u64 usage
> * Fixed alignment issue
> * Reconfigured conditional statement for interrupt setup
> * Removed unused gxp_wdt_remove function
> v3:
> * Put into proper patchset format
> v2:
> * No change
> ---
>   drivers/watchdog/Kconfig   |  11 +++
>   drivers/watchdog/Makefile  |   1 +
>   drivers/watchdog/gxp-wdt.c | 166 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 178 insertions(+)
>   create mode 100644 drivers/watchdog/gxp-wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index c4e82a8d863f..a591cc6aa152 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1820,6 +1820,17 @@ config RALINK_WDT
>   	help
>   	  Hardware driver for the Ralink SoC Watchdog Timer.
>   
> +config GXP_WATCHDOG
> +	tristate "HPE GXP watchdog support"
> +	depends on ARCH_HPE_GXP
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include support for the watchdog timer
> +	  in HPE GXP SoCs.
> +
> +	  To compile this driver as a module, choose M here.
> +	  The module will be called gxp-wdt.
> +
>   config MT7621_WDT
>   	tristate "Mediatek SoC watchdog"
>   	select WATCHDOG_CORE
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index f7da867e8782..e2acf3a0d0fc 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -92,6 +92,7 @@ obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
>   obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
>   obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
>   obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
> +obj-$(CONFIG_GXP_WATCHDOG) += gxp-wdt.o
>   obj-$(CONFIG_VISCONTI_WATCHDOG) += visconti_wdt.o
>   obj-$(CONFIG_MSC313E_WATCHDOG) += msc313e_wdt.o
>   obj-$(CONFIG_APPLE_WATCHDOG) += apple_wdt.o
> diff --git a/drivers/watchdog/gxp-wdt.c b/drivers/watchdog/gxp-wdt.c
> new file mode 100644
> index 000000000000..f45ab9a826d6
> --- /dev/null
> +++ b/drivers/watchdog/gxp-wdt.c
> @@ -0,0 +1,166 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2022 Hewlett-Packard Enterprise Development Company, L.P. */
> +
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>

Where are those of_ includes used ?

> +#include <linux/types.h>
> +#include <linux/watchdog.h>
> +
> +#define MASK_WDGCS_ENABLE	0x01
> +#define MASK_WDGCS_RELOAD	0x04
> +#define MASK_WDGCS_NMIEN	0x08
> +#define MASK_WDGCS_WARN		0x80
> +
> +#define WDT_MAX_TIMEOUT_MS	655000

Shouldn't that be 655350 ?

> +#define WDT_DEFAULT_TIMEOUT	30
> +#define SECS_TO_WDOG_TICKS(x) ((x) * 100)
> +#define WDOG_TICKS_TO_SECS(x) ((x) / 100)
> +
> +#define GXP_WDT_CNT_OFS		0x10
> +#define GXP_WDT_CTRL_OFS	0x16
> +
> +struct gxp_wdt {
> +	void __iomem *base;
> +	struct watchdog_device wdd;
> +};
> +
> +static void gxp_wdt_enable_reload(struct gxp_wdt *drvdata)
> +{
> +	u8 val;
> +
> +	val = readb(drvdata->base + GXP_WDT_CTRL_OFS);
> +	val |= (MASK_WDGCS_ENABLE | MASK_WDGCS_RELOAD);
> +	writeb(val, drvdata->base + GXP_WDT_CTRL_OFS);
> +}
> +
> +static int gxp_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +
> +	writew(SECS_TO_WDOG_TICKS(wdd->timeout), drvdata->base + GXP_WDT_CNT_OFS);
> +	gxp_wdt_enable_reload(drvdata);
> +	return 0;
> +}
> +
> +static int gxp_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +	u8 val;
> +
> +	val = readb_relaxed(drvdata->base + GXP_WDT_CTRL_OFS);
> +	val &= ~MASK_WDGCS_ENABLE;
> +	writeb(val, drvdata->base + GXP_WDT_CTRL_OFS);
> +	return 0;
> +}
> +
> +static int gxp_wdt_set_timeout(struct watchdog_device *wdd,
> +			       unsigned int timeout)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +	u32 actual;
> +
> +	wdd->timeout = timeout;
> +	actual = min(timeout, wdd->max_hw_heartbeat_ms / 1000);
> +	writew(SECS_TO_WDOG_TICKS(actual), drvdata->base + GXP_WDT_CNT_OFS);

First, the accuracy of actual is reduced to 1 second, then SECS_TO_WDOG_TICKS()
multiplies the result with 100, meaning the actual accuracy is 10ms. Why not
just use 10 ms ?

	actual = min(timeout * 100, wdd->max_hw_heartbeat_ms / 10);
	writew(actual, drvdata->base + GXP_WDT_CNT_OFS);

I guess it doesn't matter much since max_hw_heartbeat_ms is really a constant
rounded down to seconds, it just looks odd.

> +
> +	return 0;
> +}
> +
> +static unsigned int gxp_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +	u32 val = readw(drvdata->base + GXP_WDT_CNT_OFS);
> +
> +	return WDOG_TICKS_TO_SECS(val);
> +}
> +
> +static int gxp_wdt_ping(struct watchdog_device *wdd)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +
> +	gxp_wdt_enable_reload(drvdata);
> +	return 0;
> +}
> +
> +static int gxp_restart(struct watchdog_device *wdd, unsigned long action,
> +		       void *data)
> +{
> +	struct gxp_wdt *drvdata = watchdog_get_drvdata(wdd);
> +
> +	writew(10, drvdata->base + GXP_WDT_CNT_OFS);

Doesn't that translate to 100 ms timeout ? Why such a large reboot delay
instead of writing 1 ?

> +	gxp_wdt_enable_reload(drvdata);
> +	mdelay(100);
> +	return 0;
> +}
> +
> +static const struct watchdog_ops gxp_wdt_ops = {
> +	.owner =	THIS_MODULE,
> +	.start =	gxp_wdt_start,
> +	.stop =		gxp_wdt_stop,
> +	.ping =		gxp_wdt_ping,
> +	.set_timeout =	gxp_wdt_set_timeout,
> +	.get_timeleft =	gxp_wdt_get_timeleft,
> +	.restart =	gxp_restart,
> +};
> +
> +static const struct watchdog_info gxp_wdt_info = {
> +	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
> +	.identity = "HPE GXP Watchdog timer",
> +};
> +
> +static int gxp_wdt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct gxp_wdt *drvdata;
> +	int err;
> +	u8 val;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(struct gxp_wdt), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->base = (void __iomem *)dev->platform_data;

I'd personaly prefer if the address was passed as resource.

> +
> +	drvdata->wdd.info = &gxp_wdt_info;
> +	drvdata->wdd.ops = &gxp_wdt_ops;
> +	drvdata->wdd.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT_MS;
> +	drvdata->wdd.parent = dev;
> +	drvdata->wdd.timeout = WDT_DEFAULT_TIMEOUT;
> +
> +	watchdog_set_drvdata(&drvdata->wdd, drvdata);
> +	watchdog_set_nowayout(&drvdata->wdd, WATCHDOG_NOWAYOUT);
> +
> +	val = readb(drvdata->base + GXP_WDT_CTRL_OFS);
> +
> +	if (val & MASK_WDGCS_ENABLE)
> +		set_bit(WDOG_HW_RUNNING, &drvdata->wdd.status);
> +
> +	watchdog_set_restart_priority(&drvdata->wdd, 128);
> +
> +	watchdog_stop_on_reboot(&drvdata->wdd);
> +	err = devm_watchdog_register_device(dev, &drvdata->wdd);
> +	if (err) {
> +		dev_err(dev, "Failed to register watchdog device");
> +		return err;
> +	}
> +
> +	dev_info(dev, "HPE GXP watchdog timer");
> +
> +	return 0;
> +}
> +
> +static struct platform_driver gxp_wdt_driver = {
> +	.probe = gxp_wdt_probe,
> +	.driver = {
> +		.name =	"gxp-wdt",
> +	},
> +};
> +module_platform_driver(gxp_wdt_driver);
> +
> +MODULE_AUTHOR("Nick Hawkins <nick.hawkins@hpe.com>");
> +MODULE_AUTHOR("Jean-Marie Verdun <verdun@hpe.com>");
> +MODULE_DESCRIPTION("Driver for GXP watchdog timer");