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