1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * ARM Secure Monitor Call watchdog driver
  4 *
  5 * Copyright 2020 Google LLC.
  6 * Julius Werner <jwerner@chromium.org>
  7 * Based on mtk_wdt.c
  8 */
  9
 10#include <linux/arm-smccc.h>
 11#include <linux/err.h>
 12#include <linux/module.h>
 13#include <linux/moduleparam.h>
 14#include <linux/of.h>
 15#include <linux/platform_device.h>
 16#include <linux/types.h>
 17#include <linux/watchdog.h>
 18#include <uapi/linux/psci.h>
 19
 20#define DRV_NAME		"arm_smc_wdt"
 21#define DRV_VERSION		"1.0"
 22
 23enum smcwd_call {
 24	SMCWD_INIT		= 0,
 25	SMCWD_SET_TIMEOUT	= 1,
 26	SMCWD_ENABLE		= 2,
 27	SMCWD_PET		= 3,
 28	SMCWD_GET_TIMELEFT	= 4,
 29};
 30
 31static bool nowayout = WATCHDOG_NOWAYOUT;
 32static unsigned int timeout;
 33
 34static int smcwd_call(struct watchdog_device *wdd, enum smcwd_call call,
 35		      unsigned long arg, struct arm_smccc_res *res)
 36{
 37	struct arm_smccc_res local_res;
 38
 39	if (!res)
 40		res = &local_res;
 41
 42	arm_smccc_smc((u32)(uintptr_t)watchdog_get_drvdata(wdd), call, arg, 0,
 43		      0, 0, 0, 0, res);
 44
 45	if (res->a0 == PSCI_RET_NOT_SUPPORTED)
 46		return -ENODEV;
 47	if (res->a0 == PSCI_RET_INVALID_PARAMS)
 48		return -EINVAL;
 49	if (res->a0 != PSCI_RET_SUCCESS)
 50		return -EIO;
 51	return 0;
 52}
 53
 54static int smcwd_ping(struct watchdog_device *wdd)
 55{
 56	return smcwd_call(wdd, SMCWD_PET, 0, NULL);
 57}
 58
 59static unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
 60{
 61	struct arm_smccc_res res;
 62
 63	smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, &res);
 64	if (res.a0)
 65		return 0;
 66	return res.a1;
 67}
 68
 69static int smcwd_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
 70{
 71	int res;
 72
 73	res = smcwd_call(wdd, SMCWD_SET_TIMEOUT, timeout, NULL);
 74	if (!res)
 75		wdd->timeout = timeout;
 76	return res;
 77}
 78
 79static int smcwd_stop(struct watchdog_device *wdd)
 80{
 81	return smcwd_call(wdd, SMCWD_ENABLE, 0, NULL);
 82}
 83
 84static int smcwd_start(struct watchdog_device *wdd)
 85{
 86	return smcwd_call(wdd, SMCWD_ENABLE, 1, NULL);
 87}
 88
 89static const struct watchdog_info smcwd_info = {
 90	.identity	= DRV_NAME,
 91	.options	= WDIOF_SETTIMEOUT |
 92			  WDIOF_KEEPALIVEPING |
 93			  WDIOF_MAGICCLOSE,
 94};
 95
 96static const struct watchdog_ops smcwd_ops = {
 97	.start		= smcwd_start,
 98	.stop		= smcwd_stop,
 99	.ping		= smcwd_ping,
100	.set_timeout	= smcwd_set_timeout,
101};
102
103static const struct watchdog_ops smcwd_timeleft_ops = {
104	.start		= smcwd_start,
105	.stop		= smcwd_stop,
106	.ping		= smcwd_ping,
107	.set_timeout	= smcwd_set_timeout,
108	.get_timeleft	= smcwd_get_timeleft,
109};
110
111static int smcwd_probe(struct platform_device *pdev)
112{
113	struct watchdog_device *wdd;
114	int err;
115	struct arm_smccc_res res;
116	u32 smc_func_id;
117
118	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
119	if (!wdd)
120		return -ENOMEM;
121	platform_set_drvdata(pdev, wdd);
122
123	if (of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
124				 &smc_func_id))
125		smc_func_id = 0x82003D06;
126	watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);
127
128	err = smcwd_call(wdd, SMCWD_INIT, 0, &res);
129	if (err < 0)
130		return err;
131
132	wdd->info = &smcwd_info;
133	/* get_timeleft is optional */
134	if (smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, NULL))
135		wdd->ops = &smcwd_ops;
136	else
137		wdd->ops = &smcwd_timeleft_ops;
138	wdd->timeout = res.a2;
139	wdd->max_timeout = res.a2;
140	wdd->min_timeout = res.a1;
141	wdd->parent = &pdev->dev;
142
143	watchdog_stop_on_reboot(wdd);
144	watchdog_stop_on_unregister(wdd);
145	watchdog_set_nowayout(wdd, nowayout);
146	watchdog_init_timeout(wdd, timeout, &pdev->dev);
147	err = smcwd_set_timeout(wdd, wdd->timeout);
148	if (err)
149		return err;
150
151	err = devm_watchdog_register_device(&pdev->dev, wdd);
152	if (err)
153		return err;
154
155	dev_info(&pdev->dev,
156		 "Watchdog registered (timeout=%d sec, nowayout=%d)\n",
157		 wdd->timeout, nowayout);
158
159	return 0;
160}
161
162static const struct of_device_id smcwd_dt_ids[] = {
163	{ .compatible = "arm,smc-wdt" },
164	{}
165};
166MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
167
168static struct platform_driver smcwd_driver = {
169	.probe		= smcwd_probe,
170	.driver		= {
171		.name		= DRV_NAME,
172		.of_match_table	= smcwd_dt_ids,
173	},
174};
175
176module_platform_driver(smcwd_driver);
177
178module_param(timeout, uint, 0);
179MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
180
181module_param(nowayout, bool, 0);
182MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
183			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
184
185MODULE_LICENSE("GPL");
186MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
187MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
188MODULE_VERSION(DRV_VERSION);