Message-ID: <55DA8F7E.4080002@roeck-us.net>
Date:	Sun, 23 Aug 2015 20:29:02 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Justin Chen <justinpopo6@...il.com>, linux-kernel@...r.kernel.org
CC:	feedback-list@...adcom.com, devicetree@...r.kernel.org,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org, wim@...ana.be,
	linux-watchdog@...r.kernel.org
Subject: Re: [PATCH 2/2] watchdog: Watchdog driver for Broadcom Set-Top Box

Hi Justin,

On 08/20/2015 10:41 AM, Justin Chen wrote:
> Watchdog driver for Broadcom 7038 and newer chips.
>
> Signed-off-by: Justin Chen <justinpopo6@...il.com>

Looks pretty good. Couple of comments below.

Thanks,
Guenter

> ---
>   drivers/watchdog/Kconfig       |   8 ++
>   drivers/watchdog/Makefile      |   1 +
>   drivers/watchdog/bcm7038_wdt.c | 253 +++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 262 insertions(+)
>   create mode 100644 drivers/watchdog/bcm7038_wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 241fafd..4fbe8ab 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1291,6 +1291,14 @@ config BCM_KONA_WDT_DEBUG
>
>   	  If in doubt, say 'N'.
>
> +config BCM7038_WDT
> +	tristate "BCM7038 Watchdog"
> +	select WATCHDOG_CORE
> +	help
> +	 Watchdog driver for the built-in hardware in Broadcom 7038 SoCs.
> +
> +	 Say 'Y or 'M' here to enable the driver.
> +
>   config IMGPDC_WDT
>   	tristate "Imagination Technologies PDC Watchdog Timer"
>   	depends on HAS_IOMEM
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 59ea9a1..65d4169 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -66,6 +66,7 @@ obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
>   obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
>   obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
>   obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
> +obj-$(CONFIG_BCM7038_WDT) += bcm7038_wdt.o
>
Can you try to insert this in alphabetic order ?

>   # AVR32 Architecture
>   obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
> diff --git a/drivers/watchdog/bcm7038_wdt.c b/drivers/watchdog/bcm7038_wdt.c
> new file mode 100644
> index 0000000..a70730b
> --- /dev/null
> +++ b/drivers/watchdog/bcm7038_wdt.c
> @@ -0,0 +1,253 @@
> +/*
> + * Copyright (C) 2015 Broadcom Corporation
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * 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.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/platform_device.h>
> +#include <linux/watchdog.h>
> +#include <linux/clk.h>
> +#include <linux/of.h>
> +#include <linux/pm.h>
> +
Please order include files in alphabetic order.

> +#define WDT_START_1		0xff00
> +#define WDT_START_2		0x00ff
> +#define WDT_STOP_1		0xee00
> +#define WDT_STOP_2		0x00ee
> +
> +#define WDT_TIMEOUT_REG		0x0
> +#define WDT_CMD_REG		0x4
> +
> +#define WDT_MIN_TIMEOUT		1 /* seconds */
> +#define WDT_DEFAULT_TIMEOUT	30 /* seconds */
> +#define WDT_DEFAULT_RATE	27000000
> +
> +struct bcm7038_watchdog {
> +	void __iomem		*reg;

'base' would be a better name for this variable.

> +	struct clk		*wdt_clk;
> +	struct watchdog_device	wdd;
> +	u32			hz;

How about "rate" ?

> +};
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +
> +static unsigned long bcm7038_wdt_get_rate(struct bcm7038_watchdog *wdt)
> +{
> +	/* if clock is missing return hz */
> +	if (!wdt->wdt_clk)
> +		return wdt->hz;
> +
> +	return clk_get_rate(wdt->wdt_clk);
> +
Unnecessary empty line.

This is unnecessary complex. See below.

> +}
> +
> +static void bcm7038_wdt_set_timeout_reg(struct watchdog_device *wdog)
> +{
> +	struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog);
> +	u32 timeout;
> +
> +	timeout = bcm7038_wdt_get_rate(wdt) * wdog->timeout;
> +
> +	writel(timeout, wdt->reg + WDT_TIMEOUT_REG);
> +}
> +
> +static int bcm7038_wdt_ping(struct watchdog_device *wdog)
> +{
> +	struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog);
> +
> +	writel(WDT_START_1, wdt->reg + WDT_CMD_REG);
> +	writel(WDT_START_2, wdt->reg + WDT_CMD_REG);
> +
> +	return 0;
> +}
> +
> +static int bcm7038_wdt_start(struct watchdog_device *wdog)
> +{
> +	bcm7038_wdt_set_timeout_reg(wdog);
> +	bcm7038_wdt_ping(wdog);
> +
> +	return 0;
> +}
> +
> +static int bcm7038_wdt_stop(struct watchdog_device *wdog)
> +{
> +	struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog);
> +
> +	writel(WDT_STOP_1, wdt->reg + WDT_CMD_REG);
> +	writel(WDT_STOP_2, wdt->reg + WDT_CMD_REG);
> +
> +	return 0;
> +}
> +
> +static int bcm7038_wdt_set_timeout(struct watchdog_device *wdog,
> +					unsigned int t)

Please align continuation lines to '('.

> +{
> +	if (watchdog_timeout_invalid(wdog, t))
> +		return -EINVAL;
> +
Unnecessary; checked by infrastructure.

> +	/* Can't modify timeout value if watchdog timer is running */
> +	bcm7038_wdt_stop(wdog);
> +	wdog->timeout = t;
> +	bcm7038_wdt_start(wdog);
> +
> +	return 0;
> +}
> +
> +static unsigned int bcm7038_wdt_get_timeleft(struct watchdog_device *wdog)
> +{
> +	struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog);
> +	u32 time_left;
> +
> +	time_left = readl(wdt->reg + WDT_CMD_REG);
> +
> +	return time_left / bcm7038_wdt_get_rate(wdt);
> +}
> +
> +static struct watchdog_info bcm7038_wdt_info = {
> +	.identity	= "Broadcom Watchdog Timer",

I would suggest "Broadcom BCM7038 Watchdog Timer", to be in line with
other Broadcom watchdog drivers.

> +	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> +				WDIOF_MAGICCLOSE
> +};
> +
> +static struct watchdog_ops bcm7038_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= bcm7038_wdt_start,
> +	.stop		= bcm7038_wdt_stop,
> +	.set_timeout	= bcm7038_wdt_set_timeout,
> +	.get_timeleft	= bcm7038_wdt_get_timeleft,
> +};
> +
> +static int bcm7038_wdt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct bcm7038_watchdog *wdt;
> +	struct resource *res;
> +	unsigned long wdt_rate;
> +	int err;
> +
> +	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, wdt);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	wdt->reg = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(wdt->reg))
> +		return PTR_ERR(wdt->reg);
> +
> +	wdt->wdt_clk = devm_clk_get(dev, NULL);
> +	/* If unable to get clock, set clock to NULL */
> +	if (IS_ERR(wdt->wdt_clk)) {
> +		wdt->wdt_clk = NULL;
> +		err = of_property_read_u32(np, "clock-frequency", &wdt->hz);
> +		if (err) {
> +			wdt->hz = WDT_DEFAULT_RATE;
> +			dev_info(dev, "Using default frequency\n");
> +		}
> +	}

Way too complex. I would suggest to use something like

	if (!IS_ERR(clk)) {
		wdt->hz = clk_get_rate(wdt->wdt_clk);
	} else {
		wdt->wdt_clk = NULL;
		err = of_property_read_u32(np, "clock-frequency", &wdt->hz);
		if (err) {
			wdt->hz = WDT_DEFAULT_RATE;
			dev_info(dev, "Can not determine clock frequency, using default\n");
		}
	}

Then just use wdt->hz (or better wdt->rate) in the rest of the code.

Some drivers check if clk_get_rate() returns 0; might be a good idea to do this here
as well.

> +
> +	clk_prepare_enable(wdt->wdt_clk);
> +
You may have to move above code to here, and there is no need to call
clk_prepare_enable() if the clock isn't there.

> +	wdt_rate = bcm7038_wdt_get_rate(wdt);
> +

With the above, I think bcm7038_wdt_get_rate() is unnecessary. You can just use wdt->hz.

> +	wdt->wdd.info		= &bcm7038_wdt_info;
> +	wdt->wdd.ops		= &bcm7038_wdt_ops;
> +	wdt->wdd.min_timeout	= WDT_MIN_TIMEOUT;
> +	wdt->wdd.timeout	= WDT_DEFAULT_TIMEOUT;
> +	wdt->wdd.max_timeout	= (0xffffffff / wdt_rate);

Unnecessary ( ).

> +	wdt->wdd.parent		= dev;
> +	watchdog_set_drvdata(&wdt->wdd, wdt);
> +
> +	err = watchdog_register_device(&wdt->wdd);
> +	if (err) {
> +		dev_err(dev, "Failed to register watchdog device\n");
> +		return err;
> +	}
> +
> +	dev_info(dev, "Registered Broadcom Watchdog\n");
> +
BCM7038 ?

> +	return 0;
> +}
> +
> +static int bcm7038_wdt_remove(struct platform_device *pdev)
> +{
> +	struct bcm7038_watchdog *wdt = platform_get_drvdata(pdev);
> +
> +	if (!nowayout)
> +		bcm7038_wdt_stop(&wdt->wdd);
> +
> +	watchdog_unregister_device(&wdt->wdd);
> +	clk_disable_unprepare(wdt->wdt_clk);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int bcm7038_wdt_suspend(struct device *dev)
> +{
> +	struct bcm7038_watchdog *wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		return bcm7038_wdt_stop(&wdt->wdd);
> +
> +	return 0;
> +}
> +
> +static int bcm7038_wdt_resume(struct device *dev)
> +{
> +	struct bcm7038_watchdog *wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		return bcm7038_wdt_start(&wdt->wdd);
> +
> +	return 0;
> +}
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(bcm7038_wdt_pm_ops, bcm7038_wdt_suspend,
> +				bcm7038_wdt_resume);
> +
> +static void bcm7038_wdt_shutdown(struct platform_device *pdev)
> +{
> +	struct bcm7038_watchdog *wdt = platform_get_drvdata(pdev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		bcm7038_wdt_stop(&wdt->wdd);
> +}
> +
> +static const struct of_device_id bcm7038_wdt_match[] = {
> +	{ .compatible = "brcm,bcm7038-wdt" },
> +	{},
> +};
> +
> +static struct platform_driver bcm7038_wdt_driver = {
> +	.probe		= bcm7038_wdt_probe,
> +	.remove		= bcm7038_wdt_remove,
> +	.shutdown	= bcm7038_wdt_shutdown,
> +	.driver		= {
> +		.name		= "bcm7038-wdt",
> +		.of_match_table	= bcm7038_wdt_match,
> +		.pm		= &bcm7038_wdt_pm_ops,
> +	}
> +};
> +module_platform_driver(bcm7038_wdt_driver);
> +
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Driver for Broadcom 7038 SoCs Watchdog");
> +MODULE_AUTHOR("Justin Chen");
>

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