1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2006-2007 PA Semi, Inc
4  *
5  * Maintained by: Olof Johansson <olof@lixom.net>
6  *
7  * Driver for the PWRficient onchip rng
8  */
9 
10 #include <linux/module.h>
11 #include <linux/kernel.h>
12 #include <linux/platform_device.h>
13 #include <linux/hw_random.h>
14 #include <linux/delay.h>
15 #include <linux/of_address.h>
16 #include <linux/of_platform.h>
17 #include <linux/io.h>
18 
19 #define SDCRNG_CTL_REG			0x00
20 #define   SDCRNG_CTL_FVLD_M		0x0000f000
21 #define   SDCRNG_CTL_FVLD_S		12
22 #define   SDCRNG_CTL_KSZ		0x00000800
23 #define   SDCRNG_CTL_RSRC_CRG		0x00000010
24 #define   SDCRNG_CTL_RSRC_RRG		0x00000000
25 #define   SDCRNG_CTL_CE			0x00000004
26 #define   SDCRNG_CTL_RE			0x00000002
27 #define   SDCRNG_CTL_DR			0x00000001
28 #define   SDCRNG_CTL_SELECT_RRG_RNG	(SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
29 #define   SDCRNG_CTL_SELECT_CRG_RNG	(SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
30 #define SDCRNG_VAL_REG			0x20
31 
32 #define MODULE_NAME "pasemi_rng"
33 
34 static int pasemi_rng_data_present(struct hwrng *rng, int wait)
35 {
36 	void __iomem *rng_regs = (void __iomem *)rng->priv;
37 	int data, i;
38 
39 	for (i = 0; i < 20; i++) {
40 		data = (in_le32(rng_regs + SDCRNG_CTL_REG)
41 			& SDCRNG_CTL_FVLD_M) ? 1 : 0;
42 		if (data || !wait)
43 			break;
44 		udelay(10);
45 	}
46 	return data;
47 }
48 
49 static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
50 {
51 	void __iomem *rng_regs = (void __iomem *)rng->priv;
52 	*data = in_le32(rng_regs + SDCRNG_VAL_REG);
53 	return 4;
54 }
55 
56 static int pasemi_rng_init(struct hwrng *rng)
57 {
58 	void __iomem *rng_regs = (void __iomem *)rng->priv;
59 	u32 ctl;
60 
61 	ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
62 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
63 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);
64 
65 	return 0;
66 }
67 
68 static void pasemi_rng_cleanup(struct hwrng *rng)
69 {
70 	void __iomem *rng_regs = (void __iomem *)rng->priv;
71 	u32 ctl;
72 
73 	ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
74 	out_le32(rng_regs + SDCRNG_CTL_REG,
75 		 in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
76 }
77 
78 static struct hwrng pasemi_rng = {
79 	.name		= MODULE_NAME,
80 	.init		= pasemi_rng_init,
81 	.cleanup	= pasemi_rng_cleanup,
82 	.data_present	= pasemi_rng_data_present,
83 	.data_read	= pasemi_rng_data_read,
84 };
85 
86 static int rng_probe(struct platform_device *pdev)
87 {
88 	void __iomem *rng_regs;
89 
90 	rng_regs = devm_platform_ioremap_resource(pdev, 0);
91 	if (IS_ERR(rng_regs))
92 		return PTR_ERR(rng_regs);
93 
94 	pasemi_rng.priv = (unsigned long)rng_regs;
95 
96 	pr_info("Registering PA Semi RNG\n");
97 	return devm_hwrng_register(&pdev->dev, &pasemi_rng);
98 }
99 
100 static const struct of_device_id rng_match[] = {
101 	{ .compatible      = "1682m-rng", },
102 	{ .compatible      = "pasemi,pwrficient-rng", },
103 	{ },
104 };
105 MODULE_DEVICE_TABLE(of, rng_match);
106 
107 static struct platform_driver rng_driver = {
108 	.driver = {
109 		.name = "pasemi-rng",
110 		.of_match_table = rng_match,
111 	},
112 	.probe		= rng_probe,
113 };
114 
115 module_platform_driver(rng_driver);
116 
117 MODULE_LICENSE("GPL");
118 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
119 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");
120