arm_smc_wdt.c

  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_DISABLED)
 50		return -ENODATA;
 51	if (res->a0 != PSCI_RET_SUCCESS)
 52		return -EIO;
 53	return 0;
 54}
 55
 56static int smcwd_ping(struct watchdog_device *wdd)
 57{
 58	return smcwd_call(wdd, SMCWD_PET, 0, NULL);
 59}
 60
 61static unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
 62{
 63	struct arm_smccc_res res;
 64
 65	smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, &res);
 66	if (res.a0)
 67		return 0;
 68	return res.a1;
 69}
 70
 71static int smcwd_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
 72{
 73	int res;
 74
 75	res = smcwd_call(wdd, SMCWD_SET_TIMEOUT, timeout, NULL);
 76	if (!res)
 77		wdd->timeout = timeout;
 78	return res;
 79}
 80
 81static int smcwd_stop(struct watchdog_device *wdd)
 82{
 83	return smcwd_call(wdd, SMCWD_ENABLE, 0, NULL);
 84}
 85
 86static int smcwd_start(struct watchdog_device *wdd)
 87{
 88	return smcwd_call(wdd, SMCWD_ENABLE, 1, NULL);
 89}
 90
 91static const struct watchdog_info smcwd_info = {
 92	.identity	= DRV_NAME,
 93	.options	= WDIOF_SETTIMEOUT |
 94			  WDIOF_KEEPALIVEPING |
 95			  WDIOF_MAGICCLOSE,
 96};
 97
 98static const struct watchdog_ops smcwd_ops = {
 99	.start		= smcwd_start,
100	.stop		= smcwd_stop,
101	.ping		= smcwd_ping,
102	.set_timeout	= smcwd_set_timeout,
103};
104
105static const struct watchdog_ops smcwd_timeleft_ops = {
106	.start		= smcwd_start,
107	.stop		= smcwd_stop,
108	.ping		= smcwd_ping,
109	.set_timeout	= smcwd_set_timeout,
110	.get_timeleft	= smcwd_get_timeleft,
111};
112
113static int smcwd_probe(struct platform_device *pdev)
114{
115	struct watchdog_device *wdd;
116	int err;
117	struct arm_smccc_res res;
118	u32 smc_func_id;
119
120	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
121	if (!wdd)
122		return -ENOMEM;
123	platform_set_drvdata(pdev, wdd);
124
125	if (of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
126				 &smc_func_id))
127		smc_func_id = 0x82003D06;
128	watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);
129
130	err = smcwd_call(wdd, SMCWD_INIT, 0, &res);
131	if (err < 0)
132		return err;
133
134	wdd->info = &smcwd_info;
135	/* get_timeleft is optional */
136	err = smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, NULL);
137	switch (err) {
138	case 0:
139		set_bit(WDOG_HW_RUNNING, &wdd->status);
140		fallthrough;
141	case -ENODATA:
142		wdd->ops = &smcwd_timeleft_ops;
143		break;
144	default:
145		wdd->ops = &smcwd_ops;
146		break;
147	}
148
149	wdd->timeout = res.a2;
150	wdd->max_timeout = res.a2;
151	wdd->min_timeout = res.a1;
152	wdd->parent = &pdev->dev;
153
154	watchdog_stop_on_reboot(wdd);
155	watchdog_stop_on_unregister(wdd);
156	watchdog_set_nowayout(wdd, nowayout);
157	watchdog_init_timeout(wdd, timeout, &pdev->dev);
158	err = smcwd_set_timeout(wdd, wdd->timeout);
159	if (err)
160		return err;
161
162	err = devm_watchdog_register_device(&pdev->dev, wdd);
163	if (err)
164		return err;
165
166	dev_info(&pdev->dev,
167		 "Watchdog registered (timeout=%d sec, nowayout=%d)\n",
168		 wdd->timeout, nowayout);
169
170	return 0;
171}
172
173static const struct of_device_id smcwd_dt_ids[] = {
174	{ .compatible = "arm,smc-wdt" },
175	{}
176};
177MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
178
179static struct platform_driver smcwd_driver = {
180	.probe		= smcwd_probe,
181	.driver		= {
182		.name		= DRV_NAME,
183		.of_match_table	= smcwd_dt_ids,
184	},
185};
186
187module_platform_driver(smcwd_driver);
188
189module_param(timeout, uint, 0);
190MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
191
192module_param(nowayout, bool, 0);
193MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
194			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
195
196MODULE_LICENSE("GPL");
197MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
198MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
199MODULE_VERSION(DRV_VERSION);