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/*
* Renesas RZ/A Series WDT Driver
*
* Copyright (C) 2017 Renesas Electronics America, Inc.
* Copyright (C) 2017 Chris Brandt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#define DEFAULT_TIMEOUT 30
/* Watchdog Timer Registers */
#define WTCSR 0
#define WTCSR_MAGIC 0xA500
#define WTSCR_WT BIT(6)
#define WTSCR_TME BIT(5)
#define WTSCR_CKS(i) (i)
#define WTCNT 2
#define WTCNT_MAGIC 0x5A00
#define WRCSR 4
#define WRCSR_MAGIC 0x5A00
#define WRCSR_RSTE BIT(6)
#define WRCSR_CLEAR_WOVF 0xA500 /* special value */
struct rza_wdt {
struct watchdog_device wdev;
void __iomem *base;
struct clk *clk;
};
static int rza_wdt_start(struct watchdog_device *wdev)
{
struct rza_wdt *priv = watchdog_get_drvdata(wdev);
/* Stop timer */
writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
/* Must dummy read WRCSR:WOVF at least once before clearing */
readb(priv->base + WRCSR);
writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
/*
* Start timer with slowest clock source and reset option enabled.
*/
writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
writew(WTCNT_MAGIC | 0, priv->base + WTCNT);
writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME | WTSCR_CKS(7),
priv->base + WTCSR);
return 0;
}
static int rza_wdt_stop(struct watchdog_device *wdev)
{
struct rza_wdt *priv = watchdog_get_drvdata(wdev);
writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
return 0;
}
static int rza_wdt_ping(struct watchdog_device *wdev)
{
struct rza_wdt *priv = watchdog_get_drvdata(wdev);
writew(WTCNT_MAGIC | 0, priv->base + WTCNT);
return 0;
}
static int rza_wdt_restart(struct watchdog_device *wdev, unsigned long action,
void *data)
{
struct rza_wdt *priv = watchdog_get_drvdata(wdev);
/* Stop timer */
writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
/* Must dummy read WRCSR:WOVF at least once before clearing */
readb(priv->base + WRCSR);
writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
/*
* Start timer with fastest clock source and only 1 clock left before
* overflow with reset option enabled.
*/
writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
writew(WTCNT_MAGIC | 255, priv->base + WTCNT);
writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, priv->base + WTCSR);
/*
* Actually make sure the above sequence hits hardware before sleeping.
*/
wmb();
/* Wait for WDT overflow (reset) */
udelay(20);
return 0;
}
static const struct watchdog_info rza_wdt_ident = {
.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
.identity = "Renesas RZ/A WDT Watchdog",
};
static const struct watchdog_ops rza_wdt_ops = {
.owner = THIS_MODULE,
.start = rza_wdt_start,
.stop = rza_wdt_stop,
.ping = rza_wdt_ping,
.restart = rza_wdt_restart,
};
static int rza_wdt_probe(struct platform_device *pdev)
{
struct rza_wdt *priv;
struct resource *res;
unsigned long rate;
int ret;
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 < 16384) {
dev_err(&pdev->dev, "invalid clock rate (%ld)\n", rate);
return -ENOENT;
}
/* Assume slowest clock rate possible (CKS=7) */
rate /= 16384;
priv->wdev.info = &rza_wdt_ident,
priv->wdev.ops = &rza_wdt_ops,
priv->wdev.parent = &pdev->dev;
/*
* Since the max possible timeout of our 8-bit count register is less
* than a second, we must use max_hw_heartbeat_ms.
*/
priv->wdev.max_hw_heartbeat_ms = (1000 * U8_MAX) / rate;
dev_dbg(&pdev->dev, "max hw timeout of %dms\n",
priv->wdev.max_hw_heartbeat_ms);
priv->wdev.min_timeout = 1;
priv->wdev.timeout = DEFAULT_TIMEOUT;
watchdog_init_timeout(&priv->wdev, 0, &pdev->dev);
watchdog_set_drvdata(&priv->wdev, priv);
ret = devm_watchdog_register_device(&pdev->dev, &priv->wdev);
if (ret)
dev_err(&pdev->dev, "Cannot register watchdog device\n");
return ret;
}
static const struct of_device_id rza_wdt_of_match[] = {
{ .compatible = "renesas,rza-wdt", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rza_wdt_of_match);
static struct platform_driver rza_wdt_driver = {
.probe = rza_wdt_probe,
.driver = {
.name = "rza_wdt",
.of_match_table = rza_wdt_of_match,
},
};
module_platform_driver(rza_wdt_driver);
MODULE_DESCRIPTION("Renesas RZ/A WDT Driver");
MODULE_AUTHOR("Chris Brandt <chris.brandt@renesas.com>");
MODULE_LICENSE("GPL v2");
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