1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2015, Samsung Electronics Co., Ltd.
4  *
5  * Author: Marek Szyprowski <m.szyprowski@samsung.com>
6  *
7  * Simple eMMC hardware reset provider
8  */
9 #include <linux/delay.h>
10 #include <linux/kernel.h>
11 #include <linux/init.h>
12 #include <linux/platform_device.h>
13 #include <linux/module.h>
14 #include <linux/slab.h>
15 #include <linux/device.h>
16 #include <linux/err.h>
17 #include <linux/gpio/consumer.h>
18 #include <linux/reboot.h>
19 
20 #include <linux/mmc/host.h>
21 
22 #include "pwrseq.h"
23 
24 struct mmc_pwrseq_emmc {
25 	struct mmc_pwrseq pwrseq;
26 	struct notifier_block reset_nb;
27 	struct gpio_desc *reset_gpio;
28 };
29 
30 #define to_pwrseq_emmc(p) container_of(p, struct mmc_pwrseq_emmc, pwrseq)
31 
mmc_pwrseq_emmc_reset(struct mmc_host * host)32 static void mmc_pwrseq_emmc_reset(struct mmc_host *host)
33 {
34 	struct mmc_pwrseq_emmc *pwrseq =  to_pwrseq_emmc(host->pwrseq);
35 
36 	gpiod_set_value_cansleep(pwrseq->reset_gpio, 1);
37 	udelay(1);
38 	gpiod_set_value_cansleep(pwrseq->reset_gpio, 0);
39 	udelay(200);
40 }
41 
mmc_pwrseq_emmc_reset_nb(struct notifier_block * this,unsigned long mode,void * cmd)42 static int mmc_pwrseq_emmc_reset_nb(struct notifier_block *this,
43 				    unsigned long mode, void *cmd)
44 {
45 	struct mmc_pwrseq_emmc *pwrseq = container_of(this,
46 					struct mmc_pwrseq_emmc, reset_nb);
47 	gpiod_set_value(pwrseq->reset_gpio, 1);
48 	udelay(1);
49 	gpiod_set_value(pwrseq->reset_gpio, 0);
50 	udelay(200);
51 
52 	return NOTIFY_DONE;
53 }
54 
55 static const struct mmc_pwrseq_ops mmc_pwrseq_emmc_ops = {
56 	.reset = mmc_pwrseq_emmc_reset,
57 };
58 
mmc_pwrseq_emmc_probe(struct platform_device * pdev)59 static int mmc_pwrseq_emmc_probe(struct platform_device *pdev)
60 {
61 	struct mmc_pwrseq_emmc *pwrseq;
62 	struct device *dev = &pdev->dev;
63 
64 	pwrseq = devm_kzalloc(dev, sizeof(*pwrseq), GFP_KERNEL);
65 	if (!pwrseq)
66 		return -ENOMEM;
67 
68 	pwrseq->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
69 	if (IS_ERR(pwrseq->reset_gpio))
70 		return PTR_ERR(pwrseq->reset_gpio);
71 
72 	if (!gpiod_cansleep(pwrseq->reset_gpio)) {
73 		/*
74 		 * register reset handler to ensure emmc reset also from
75 		 * emergency_reboot(), priority 255 is the highest priority
76 		 * so it will be executed before any system reboot handler.
77 		 */
78 		pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb;
79 		pwrseq->reset_nb.priority = 255;
80 		register_restart_handler(&pwrseq->reset_nb);
81 	} else {
82 		dev_notice(dev, "EMMC reset pin tied to a sleepy GPIO driver; reset on emergency-reboot disabled\n");
83 	}
84 
85 	pwrseq->pwrseq.ops = &mmc_pwrseq_emmc_ops;
86 	pwrseq->pwrseq.dev = dev;
87 	pwrseq->pwrseq.owner = THIS_MODULE;
88 	platform_set_drvdata(pdev, pwrseq);
89 
90 	return mmc_pwrseq_register(&pwrseq->pwrseq);
91 }
92 
mmc_pwrseq_emmc_remove(struct platform_device * pdev)93 static int mmc_pwrseq_emmc_remove(struct platform_device *pdev)
94 {
95 	struct mmc_pwrseq_emmc *pwrseq = platform_get_drvdata(pdev);
96 
97 	unregister_restart_handler(&pwrseq->reset_nb);
98 	mmc_pwrseq_unregister(&pwrseq->pwrseq);
99 
100 	return 0;
101 }
102 
103 static const struct of_device_id mmc_pwrseq_emmc_of_match[] = {
104 	{ .compatible = "mmc-pwrseq-emmc",},
105 	{/* sentinel */},
106 };
107 
108 MODULE_DEVICE_TABLE(of, mmc_pwrseq_emmc_of_match);
109 
110 static struct platform_driver mmc_pwrseq_emmc_driver = {
111 	.probe = mmc_pwrseq_emmc_probe,
112 	.remove = mmc_pwrseq_emmc_remove,
113 	.driver = {
114 		.name = "pwrseq_emmc",
115 		.of_match_table = mmc_pwrseq_emmc_of_match,
116 	},
117 };
118 
119 module_platform_driver(mmc_pwrseq_emmc_driver);
120 MODULE_LICENSE("GPL v2");
121