watchdog: renesas-wdt: add driver

Renesas Watchdog Timer (WDT) Controller

Required properties:

- compatible : Should be "renesas,r8a7795-wdt", or "renesas,rcar-gen3-wdt"

  When compatible with the generic version, nodes must list the SoC-specific

  version corresponding to the platform first, followed by the generic

  version.

- reg : Should contain WDT registers location and length

- clocks : the clock feeding the watchdog timer.

Optional properties:

- timeout-sec : Contains the watchdog timeout in seconds

- power-domains : the power domain the WDT belongs to

Examples:

	wdt0: watchdog@e6020000 {

		compatible = "renesas,r8a7795-wdt", "renesas,rcar-gen3-wdt";

		reg = <0 0xe6020000 0 0x0c>;

		clocks = <&cpg CPG_MOD 402>;

		power-domains = <&cpg>;

		timeout-sec = <60>;

	};

	  To compile this driver as a module, choose M here: the

	  module will be called atlas7_wdt.

config RENESAS_WDT

	tristate "Renesas WDT Watchdog"

	depends on ARCH_RENESAS || COMPILE_TEST

	select WATCHDOG_CORE

	help

	  This driver adds watchdog support for the integrated watchdogs in the

	  Renesas R-Car and other SH-Mobile SoCs (usually named RWDT or SWDT).

# AVR32 Architecture

config AT32AP700X_WDT

obj-$(CONFIG_LPC18XX_WATCHDOG) += lpc18xx_wdt.o

obj-$(CONFIG_BCM7038_WDT) += bcm7038_wdt.o

obj-$(CONFIG_ATLAS7_WATCHDOG) += atlas7_wdt.o

obj-$(CONFIG_RENESAS_WDT) += renesas_wdt.o

# AVR32 Architecture

obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o

/*

 * Watchdog driver for Renesas WDT watchdog

 *

 * Copyright (C) 2015-16 Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>

 * Copyright (C) 2015-16 Renesas Electronics Corporation

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published by

 * the Free Software Foundation.

 */

#include <linux/bitops.h>

#include <linux/clk.h>

#include <linux/io.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>

#include <linux/pm_runtime.h>

#include <linux/watchdog.h>

#define RWTCNT		0

#define RWTCSRA		4

#define RWTCSRA_WOVF	BIT(4)

#define RWTCSRA_WRFLG	BIT(5)

#define RWTCSRA_TME	BIT(7)

#define RWDT_DEFAULT_TIMEOUT 60U

static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024 };

static bool nowayout = WATCHDOG_NOWAYOUT;

module_param(nowayout, bool, 0);

MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="

				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

struct rwdt_priv {

	void __iomem *base;

	struct watchdog_device wdev;

	struct clk *clk;

	unsigned int clks_per_sec;

	u8 cks;

};

static void rwdt_write(struct rwdt_priv *priv, u32 val, unsigned int reg)

{

	if (reg == RWTCNT)

		val |= 0x5a5a0000;

	else

		val |= 0xa5a5a500;

	writel_relaxed(val, priv->base + reg);

}

static int rwdt_init_timeout(struct watchdog_device *wdev)

{

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	rwdt_write(priv, 65536 - wdev->timeout * priv->clks_per_sec, RWTCNT);

	return 0;

}

static int rwdt_start(struct watchdog_device *wdev)

{

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	clk_prepare_enable(priv->clk);

	rwdt_write(priv, priv->cks, RWTCSRA);

	rwdt_init_timeout(wdev);

	while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)

		cpu_relax();

	rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);

	return 0;

}

static int rwdt_stop(struct watchdog_device *wdev)

{

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	rwdt_write(priv, priv->cks, RWTCSRA);

	clk_disable_unprepare(priv->clk);

	return 0;

}

static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev)

{

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	u16 val = readw_relaxed(priv->base + RWTCNT);

	return DIV_ROUND_CLOSEST(65536 - val, priv->clks_per_sec);

}

static const struct watchdog_info rwdt_ident = {

	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,

	.identity = "Renesas WDT Watchdog",

};

static const struct watchdog_ops rwdt_ops = {

	.owner = THIS_MODULE,

	.start = rwdt_start,

	.stop = rwdt_stop,

	.ping = rwdt_init_timeout,

	.get_timeleft = rwdt_get_timeleft,

};

static int rwdt_probe(struct platform_device *pdev)

{

	struct rwdt_priv *priv;

	struct resource *res;

	unsigned long rate;

	unsigned int clks_per_sec;

	int ret, i;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	priv->base = devm_ioremap_resource(&pdev->dev, res);

	if (IS_ERR(priv->base))

		return PTR_ERR(priv->base);

	priv->clk = devm_clk_get(&pdev->dev, NULL);

	if (IS_ERR(priv->clk))

		return PTR_ERR(priv->clk);

	rate = clk_get_rate(priv->clk);

	if (!rate)

		return -ENOENT;

	for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {

		clks_per_sec = DIV_ROUND_UP(rate, clk_divs[i]);

		if (clks_per_sec) {

			priv->clks_per_sec = clks_per_sec;

			priv->cks = i;

			break;

		}

	}

	if (!clks_per_sec) {

		dev_err(&pdev->dev, "Can't find suitable clock divider\n");

		return -ERANGE;

	}

	pm_runtime_enable(&pdev->dev);

	pm_runtime_get_sync(&pdev->dev);

	priv->wdev.info = &rwdt_ident,

	priv->wdev.ops = &rwdt_ops,

	priv->wdev.parent = &pdev->dev;

	priv->wdev.min_timeout = 1;

	priv->wdev.max_timeout = 65536 / clks_per_sec;

	priv->wdev.timeout = min(priv->wdev.max_timeout, RWDT_DEFAULT_TIMEOUT);

	platform_set_drvdata(pdev, priv);

	watchdog_set_drvdata(&priv->wdev, priv);

	watchdog_set_nowayout(&priv->wdev, nowayout);

	/* This overrides the default timeout only if DT configuration was found */

	ret = watchdog_init_timeout(&priv->wdev, 0, &pdev->dev);

	if (ret)

		dev_warn(&pdev->dev, "Specified timeout value invalid, using default\n");

	ret = watchdog_register_device(&priv->wdev);

	if (ret < 0) {

		pm_runtime_put(&pdev->dev);

		pm_runtime_disable(&pdev->dev);

		return ret;

	}

	return 0;

}

static int rwdt_remove(struct platform_device *pdev)

{

	struct rwdt_priv *priv = platform_get_drvdata(pdev);

	watchdog_unregister_device(&priv->wdev);

	pm_runtime_put(&pdev->dev);

	pm_runtime_disable(&pdev->dev);

	return 0;

}

/*

 * This driver does also fit for R-Car Gen2 (r8a779[0-4]) WDT. However, for SMP

 * to work there, one also needs a RESET (RST) driver which does not exist yet

 * due to HW issues. This needs to be solved before adding compatibles here.

 */

static const struct of_device_id rwdt_ids[] = {

	{ .compatible = "renesas,rcar-gen3-wdt", },

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(of, rwdt_ids);

static struct platform_driver rwdt_driver = {

	.driver = {

		.name = "renesas_wdt",

		.of_match_table = rwdt_ids,

	},

	.probe = rwdt_probe,

	.remove = rwdt_remove,

};

module_platform_driver(rwdt_driver);

MODULE_DESCRIPTION("Renesas WDT Watchdog Driver");

MODULE_LICENSE("GPL v2");

MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");