1/*
  2 *      intel-mid_wdt: generic Intel MID SCU watchdog driver
  3 *
  4 *      Platforms supported so far:
  5 *      - Merrifield only
  6 *
  7 *      Copyright (C) 2014 Intel Corporation. All rights reserved.
  8 *      Contact: David Cohen <david.a.cohen@linux.intel.com>
  9 *
 10 *      This program is free software; you can redistribute it and/or
 11 *      modify it under the terms of version 2 of the GNU General
 12 *      Public License as published by the Free Software Foundation.
 13 */
 14
 15#include <linux/interrupt.h>
 16#include <linux/module.h>
 17#include <linux/nmi.h>
 18#include <linux/platform_device.h>
 19#include <linux/watchdog.h>
 20#include <linux/platform_data/intel-mid_wdt.h>
 21
 22#include <asm/intel_scu_ipc.h>
 23#include <asm/intel-mid.h>
 24
 25#define IPC_WATCHDOG 0xf8
 26
 27#define MID_WDT_PRETIMEOUT		15
 28#define MID_WDT_TIMEOUT_MIN		(1 + MID_WDT_PRETIMEOUT)
 29#define MID_WDT_TIMEOUT_MAX		170
 30#define MID_WDT_DEFAULT_TIMEOUT		90
 31
 32/* SCU watchdog messages */
 33enum {
 34	SCU_WATCHDOG_START = 0,
 35	SCU_WATCHDOG_STOP,
 36	SCU_WATCHDOG_KEEPALIVE,
 37};
 38
 39static inline int wdt_command(int sub, u32 *in, int inlen)
 40{
 41	return intel_scu_ipc_command(IPC_WATCHDOG, sub, in, inlen, NULL, 0);
 42}
 43
 44static int wdt_start(struct watchdog_device *wd)
 45{
 46	struct device *dev = watchdog_get_drvdata(wd);
 47	int ret, in_size;
 48	int timeout = wd->timeout;
 49	struct ipc_wd_start {
 50		u32 pretimeout;
 51		u32 timeout;
 52	} ipc_wd_start = { timeout - MID_WDT_PRETIMEOUT, timeout };
 53
 54	/*
 55	 * SCU expects the input size for watchdog IPC to
 56	 * be based on 4 bytes
 57	 */
 58	in_size = DIV_ROUND_UP(sizeof(ipc_wd_start), 4);
 59
 60	ret = wdt_command(SCU_WATCHDOG_START, (u32 *)&ipc_wd_start, in_size);
 61	if (ret)
 62		dev_crit(dev, "error starting watchdog: %d\n", ret);
 63
 64	return ret;
 65}
 66
 67static int wdt_ping(struct watchdog_device *wd)
 68{
 69	struct device *dev = watchdog_get_drvdata(wd);
 70	int ret;
 71
 72	ret = wdt_command(SCU_WATCHDOG_KEEPALIVE, NULL, 0);
 73	if (ret)
 74		dev_crit(dev, "Error executing keepalive: %d\n", ret);
 75
 76	return ret;
 77}
 78
 79static int wdt_stop(struct watchdog_device *wd)
 80{
 81	struct device *dev = watchdog_get_drvdata(wd);
 82	int ret;
 83
 84	ret = wdt_command(SCU_WATCHDOG_STOP, NULL, 0);
 85	if (ret)
 86		dev_crit(dev, "Error stopping watchdog: %d\n", ret);
 87
 88	return ret;
 89}
 90
 91static irqreturn_t mid_wdt_irq(int irq, void *dev_id)
 92{
 93	panic("Kernel Watchdog");
 94
 95	/* This code should not be reached */
 96	return IRQ_HANDLED;
 97}
 98
 99static const struct watchdog_info mid_wdt_info = {
100	.identity = "Intel MID SCU watchdog",
101	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
102};
103
104static const struct watchdog_ops mid_wdt_ops = {
105	.owner = THIS_MODULE,
106	.start = wdt_start,
107	.stop = wdt_stop,
108	.ping = wdt_ping,
109};
110
111static int mid_wdt_probe(struct platform_device *pdev)
112{
113	struct watchdog_device *wdt_dev;
114	struct intel_mid_wdt_pdata *pdata = pdev->dev.platform_data;
115	int ret;
116
117	if (!pdata) {
118		dev_err(&pdev->dev, "missing platform data\n");
119		return -EINVAL;
120	}
121
122	if (pdata->probe) {
123		ret = pdata->probe(pdev);
124		if (ret)
125			return ret;
126	}
127
128	wdt_dev = devm_kzalloc(&pdev->dev, sizeof(*wdt_dev), GFP_KERNEL);
129	if (!wdt_dev)
130		return -ENOMEM;
131
132	wdt_dev->info = &mid_wdt_info;
133	wdt_dev->ops = &mid_wdt_ops;
134	wdt_dev->min_timeout = MID_WDT_TIMEOUT_MIN;
135	wdt_dev->max_timeout = MID_WDT_TIMEOUT_MAX;
136	wdt_dev->timeout = MID_WDT_DEFAULT_TIMEOUT;
137	wdt_dev->parent = &pdev->dev;
138
139	watchdog_set_drvdata(wdt_dev, &pdev->dev);
140
141	ret = devm_request_irq(&pdev->dev, pdata->irq, mid_wdt_irq,
142			       IRQF_SHARED | IRQF_NO_SUSPEND, "watchdog",
143			       wdt_dev);
144	if (ret) {
145		dev_err(&pdev->dev, "error requesting warning irq %d\n",
146			pdata->irq);
147		return ret;
148	}
149
150	/*
151	 * The firmware followed by U-Boot leaves the watchdog running
152	 * with the default threshold which may vary. When we get here
153	 * we should make a decision to prevent any side effects before
154	 * user space daemon will take care of it. The best option,
155	 * taking into consideration that there is no way to read values
156	 * back from hardware, is to enforce watchdog being run with
157	 * deterministic values.
158	 */
159	ret = wdt_start(wdt_dev);
160	if (ret)
161		return ret;
162
163	/* Make sure the watchdog is serviced */
164	set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
165
166	ret = devm_watchdog_register_device(&pdev->dev, wdt_dev);
167	if (ret) {
168		dev_err(&pdev->dev, "error registering watchdog device\n");
169		return ret;
170	}
171
172	dev_info(&pdev->dev, "Intel MID watchdog device probed\n");
173
174	return 0;
175}
176
177static struct platform_driver mid_wdt_driver = {
178	.probe		= mid_wdt_probe,
179	.driver		= {
180		.name	= "intel_mid_wdt",
181	},
182};
183
184module_platform_driver(mid_wdt_driver);
185
186MODULE_AUTHOR("David Cohen <david.a.cohen@linux.intel.com>");
187MODULE_DESCRIPTION("Watchdog Driver for Intel MID platform");
188MODULE_LICENSE("GPL");