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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * ST Random Number Generator Driver ST's Platforms4 *5 * Author: Pankaj Dev: <pankaj.dev@st.com>6 * Lee Jones <lee.jones@linaro.org>7 *8 * Copyright (C) 2015 STMicroelectronics (R&D) Limited9 */10 11#include <linux/clk.h>12#include <linux/delay.h>13#include <linux/hw_random.h>14#include <linux/io.h>15#include <linux/kernel.h>16#include <linux/module.h>17#include <linux/of.h>18#include <linux/platform_device.h>19#include <linux/slab.h>20 21/* Registers */22#define ST_RNG_STATUS_REG 0x2023#define ST_RNG_DATA_REG 0x2424 25/* Registers fields */26#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)27#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)28#define ST_RNG_STATUS_FIFO_FULL BIT(5)29 30#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */31#define ST_RNG_FIFO_DEPTH 432#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)33 34/*35 * Samples are documented to be available every 0.667us, so in theory36 * the 4 sample deep FIFO should take 2.668us to fill. However, during37 * thorough testing, it became apparent that filling the FIFO actually38 * takes closer to 12us. We then multiply by 2 in order to account for39 * the lack of udelay()'s reliability, suggested by Russell King.40 */41#define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2)42 43struct st_rng_data {44 void __iomem *base;45 struct hwrng ops;46};47 48static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)49{50 struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;51 u32 status;52 int i;53 54 /* Wait until FIFO is full - max 4uS*/55 for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {56 status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);57 if (status & ST_RNG_STATUS_FIFO_FULL)58 break;59 udelay(1);60 }61 62 if (i == ST_RNG_FILL_FIFO_TIMEOUT)63 return 0;64 65 for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)66 *(u16 *)(data + i) =67 readl_relaxed(ddata->base + ST_RNG_DATA_REG);68 69 return i; /* No of bytes read */70}71 72static int st_rng_probe(struct platform_device *pdev)73{74 struct st_rng_data *ddata;75 struct clk *clk;76 void __iomem *base;77 int ret;78 79 ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);80 if (!ddata)81 return -ENOMEM;82 83 base = devm_platform_ioremap_resource(pdev, 0);84 if (IS_ERR(base))85 return PTR_ERR(base);86 87 clk = devm_clk_get_enabled(&pdev->dev, NULL);88 if (IS_ERR(clk))89 return PTR_ERR(clk);90 91 ddata->ops.priv = (unsigned long)ddata;92 ddata->ops.read = st_rng_read;93 ddata->ops.name = pdev->name;94 ddata->base = base;95 96 ret = devm_hwrng_register(&pdev->dev, &ddata->ops);97 if (ret) {98 dev_err(&pdev->dev, "Failed to register HW RNG\n");99 return ret;100 }101 102 dev_info(&pdev->dev, "Successfully registered HW RNG\n");103 104 return 0;105}106 107static const struct of_device_id st_rng_match[] __maybe_unused = {108 { .compatible = "st,rng" },109 {},110};111MODULE_DEVICE_TABLE(of, st_rng_match);112 113static struct platform_driver st_rng_driver = {114 .driver = {115 .name = "st-hwrandom",116 .of_match_table = of_match_ptr(st_rng_match),117 },118 .probe = st_rng_probe,119};120 121module_platform_driver(st_rng_driver);122 123MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");124MODULE_DESCRIPTION("ST Microelectronics HW Random Number Generator");125MODULE_LICENSE("GPL v2");126