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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* PIC32 watchdog driver
*
* Joshua Henderson <joshua.henderson@microchip.com>
* Copyright (c) 2016, Microchip Technology Inc.
*/
#include <linux/clk.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/watchdog.h>
#include <asm/mach-pic32/pic32.h>
/* Watchdog Timer Registers */
#define WDTCON_REG 0x00
/* Watchdog Timer Control Register fields */
#define WDTCON_WIN_EN BIT(0)
#define WDTCON_RMCS_MASK 0x0003
#define WDTCON_RMCS_SHIFT 0x0006
#define WDTCON_RMPS_MASK 0x001F
#define WDTCON_RMPS_SHIFT 0x0008
#define WDTCON_ON BIT(15)
#define WDTCON_CLR_KEY 0x5743
/* Reset Control Register fields for watchdog */
#define RESETCON_TIMEOUT_IDLE BIT(2)
#define RESETCON_TIMEOUT_SLEEP BIT(3)
#define RESETCON_WDT_TIMEOUT BIT(4)
struct pic32_wdt {
void __iomem *regs;
void __iomem *rst_base;
struct clk *clk;
};
static inline bool pic32_wdt_is_win_enabled(struct pic32_wdt *wdt)
{
return !!(readl(wdt->regs + WDTCON_REG) & WDTCON_WIN_EN);
}
static inline u32 pic32_wdt_get_post_scaler(struct pic32_wdt *wdt)
{
u32 v = readl(wdt->regs + WDTCON_REG);
return (v >> WDTCON_RMPS_SHIFT) & WDTCON_RMPS_MASK;
}
static inline u32 pic32_wdt_get_clk_id(struct pic32_wdt *wdt)
{
u32 v = readl(wdt->regs + WDTCON_REG);
return (v >> WDTCON_RMCS_SHIFT) & WDTCON_RMCS_MASK;
}
static int pic32_wdt_bootstatus(struct pic32_wdt *wdt)
{
u32 v = readl(wdt->rst_base);
writel(RESETCON_WDT_TIMEOUT, PIC32_CLR(wdt->rst_base));
return v & RESETCON_WDT_TIMEOUT;
}
static u32 pic32_wdt_get_timeout_secs(struct pic32_wdt *wdt, struct device *dev)
{
unsigned long rate;
u32 period, ps, terminal;
rate = clk_get_rate(wdt->clk);
dev_dbg(dev, "wdt: clk_id %d, clk_rate %lu (prescale)\n",
pic32_wdt_get_clk_id(wdt), rate);
/* default, prescaler of 32 (i.e. div-by-32) is implicit. */
rate >>= 5;
if (!rate)
return 0;
/* calculate terminal count from postscaler. */
ps = pic32_wdt_get_post_scaler(wdt);
terminal = BIT(ps);
/* find time taken (in secs) to reach terminal count */
period = terminal / rate;
dev_dbg(dev,
"wdt: clk_rate %lu (postscale) / terminal %d, timeout %dsec\n",
rate, terminal, period);
return period;
}
static void pic32_wdt_keepalive(struct pic32_wdt *wdt)
{
/* write key through single half-word */
writew(WDTCON_CLR_KEY, wdt->regs + WDTCON_REG + 2);
}
static int pic32_wdt_start(struct watchdog_device *wdd)
{
struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
writel(WDTCON_ON, PIC32_SET(wdt->regs + WDTCON_REG));
pic32_wdt_keepalive(wdt);
return 0;
}
static int pic32_wdt_stop(struct watchdog_device *wdd)
{
struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
writel(WDTCON_ON, PIC32_CLR(wdt->regs + WDTCON_REG));
/*
* Cannot touch registers in the CPU cycle following clearing the
* ON bit.
*/
nop();
return 0;
}
static int pic32_wdt_ping(struct watchdog_device *wdd)
{
struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
pic32_wdt_keepalive(wdt);
return 0;
}
static const struct watchdog_ops pic32_wdt_fops = {
.owner = THIS_MODULE,
.start = pic32_wdt_start,
.stop = pic32_wdt_stop,
.ping = pic32_wdt_ping,
};
static const struct watchdog_info pic32_wdt_ident = {
.options = WDIOF_KEEPALIVEPING |
WDIOF_MAGICCLOSE | WDIOF_CARDRESET,
.identity = "PIC32 Watchdog",
};
static struct watchdog_device pic32_wdd = {
.info = &pic32_wdt_ident,
.ops = &pic32_wdt_fops,
};
static const struct of_device_id pic32_wdt_dt_ids[] = {
{ .compatible = "microchip,pic32mzda-wdt", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pic32_wdt_dt_ids);
static int pic32_wdt_drv_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
int ret;
struct watchdog_device *wdd = &pic32_wdd;
struct pic32_wdt *wdt;
wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
if (!wdt)
return -ENOMEM;
wdt->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(wdt->regs))
return PTR_ERR(wdt->regs);
wdt->rst_base = devm_ioremap(dev, PIC32_BASE_RESET, 0x10);
if (!wdt->rst_base)
return -ENOMEM;
wdt->clk = devm_clk_get_enabled(dev, NULL);
if (IS_ERR(wdt->clk)) {
dev_err(dev, "clk not found\n");
return PTR_ERR(wdt->clk);
}
if (pic32_wdt_is_win_enabled(wdt)) {
dev_err(dev, "windowed-clear mode is not supported.\n");
return -ENODEV;
}
wdd->timeout = pic32_wdt_get_timeout_secs(wdt, dev);
if (!wdd->timeout) {
dev_err(dev, "failed to read watchdog register timeout\n");
return -EINVAL;
}
dev_info(dev, "timeout %d\n", wdd->timeout);
wdd->bootstatus = pic32_wdt_bootstatus(wdt) ? WDIOF_CARDRESET : 0;
watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
watchdog_set_drvdata(wdd, wdt);
ret = devm_watchdog_register_device(dev, wdd);
if (ret)
return ret;
platform_set_drvdata(pdev, wdd);
return 0;
}
static struct platform_driver pic32_wdt_driver = {
.probe = pic32_wdt_drv_probe,
.driver = {
.name = "pic32-wdt",
.of_match_table = of_match_ptr(pic32_wdt_dt_ids),
}
};
module_platform_driver(pic32_wdt_driver);
MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
MODULE_DESCRIPTION("Microchip PIC32 Watchdog Timer");
MODULE_LICENSE("GPL");
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