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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 | // SPDX-License-Identifier: GPL-2.0-only /* * drivers/char/hw_random/timeriomem-rng.c * * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk> * * Derived from drivers/char/hw_random/omap-rng.c * Copyright 2005 (c) MontaVista Software, Inc. * Author: Deepak Saxena <dsaxena@plexity.net> * * Overview: * This driver is useful for platforms that have an IO range that provides * periodic random data from a single IO memory address. All the platform * has to do is provide the address and 'wait time' that new data becomes * available. * * TODO: add support for reading sizes other than 32bits and masking */ #include <linux/completion.h> #include <linux/delay.h> #include <linux/hrtimer.h> #include <linux/hw_random.h> #include <linux/io.h> #include <linux/ktime.h> #include <linux/module.h> #include <linux/of.h> #include <linux/platform_device.h> #include <linux/slab.h> #include <linux/time.h> #include <linux/timeriomem-rng.h> struct timeriomem_rng_private { void __iomem *io_base; ktime_t period; unsigned int present:1; struct hrtimer timer; struct completion completion; struct hwrng rng_ops; }; static int timeriomem_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait) { struct timeriomem_rng_private *priv = container_of(hwrng, struct timeriomem_rng_private, rng_ops); int retval = 0; int period_us = ktime_to_us(priv->period); /* * There may not have been enough time for new data to be generated * since the last request. If the caller doesn't want to wait, let them * bail out. Otherwise, wait for the completion. If the new data has * already been generated, the completion should already be available. */ if (!wait && !priv->present) return 0; wait_for_completion(&priv->completion); do { /* * After the first read, all additional reads will need to wait * for the RNG to generate new data. Since the period can have * a wide range of values (1us to 1s have been observed), allow * for 1% tolerance in the sleep time rather than a fixed value. */ if (retval > 0) usleep_range(period_us, period_us + max(1, period_us / 100)); *(u32 *)data = readl(priv->io_base); retval += sizeof(u32); data += sizeof(u32); max -= sizeof(u32); } while (wait && max > sizeof(u32)); /* * Block any new callers until the RNG has had time to generate new * data. */ priv->present = 0; reinit_completion(&priv->completion); hrtimer_forward_now(&priv->timer, priv->period); hrtimer_restart(&priv->timer); return retval; } static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer) { struct timeriomem_rng_private *priv = container_of(timer, struct timeriomem_rng_private, timer); priv->present = 1; complete(&priv->completion); return HRTIMER_NORESTART; } static int timeriomem_rng_probe(struct platform_device *pdev) { struct timeriomem_rng_data *pdata = pdev->dev.platform_data; struct timeriomem_rng_private *priv; struct resource *res; int err = 0; int period; if (!pdev->dev.of_node && !pdata) { dev_err(&pdev->dev, "timeriomem_rng_data is missing\n"); return -EINVAL; } /* Allocate memory for the device structure (and zero it) */ priv = devm_kzalloc(&pdev->dev, sizeof(struct timeriomem_rng_private), GFP_KERNEL); if (!priv) return -ENOMEM; platform_set_drvdata(pdev, priv); priv->io_base = devm_platform_get_and_ioremap_resource(pdev, 0, &res); if (IS_ERR(priv->io_base)) return PTR_ERR(priv->io_base); if (res->start % 4 != 0 || resource_size(res) < 4) { dev_err(&pdev->dev, "address must be at least four bytes wide and 32-bit aligned\n"); return -EINVAL; } if (pdev->dev.of_node) { int i; if (!of_property_read_u32(pdev->dev.of_node, "period", &i)) period = i; else { dev_err(&pdev->dev, "missing period\n"); return -EINVAL; } if (!of_property_read_u32(pdev->dev.of_node, "quality", &i)) priv->rng_ops.quality = i; } else { period = pdata->period; priv->rng_ops.quality = pdata->quality; } priv->period = ns_to_ktime(period * NSEC_PER_USEC); init_completion(&priv->completion); hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); priv->timer.function = timeriomem_rng_trigger; priv->rng_ops.name = dev_name(&pdev->dev); priv->rng_ops.read = timeriomem_rng_read; /* Assume random data is already available. */ priv->present = 1; complete(&priv->completion); err = devm_hwrng_register(&pdev->dev, &priv->rng_ops); if (err) { dev_err(&pdev->dev, "problem registering\n"); return err; } dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n", priv->io_base, period); return 0; } static int timeriomem_rng_remove(struct platform_device *pdev) { struct timeriomem_rng_private *priv = platform_get_drvdata(pdev); hrtimer_cancel(&priv->timer); return 0; } static const struct of_device_id timeriomem_rng_match[] = { { .compatible = "timeriomem_rng" }, {}, }; MODULE_DEVICE_TABLE(of, timeriomem_rng_match); static struct platform_driver timeriomem_rng_driver = { .driver = { .name = "timeriomem_rng", .of_match_table = timeriomem_rng_match, }, .probe = timeriomem_rng_probe, .remove = timeriomem_rng_remove, }; module_platform_driver(timeriomem_rng_driver); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>"); MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver"); |