mirror of https://gitee.com/openkylin/linux.git
214 lines
5.4 KiB
C
214 lines
5.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* drivers/char/hw_random/timeriomem-rng.c
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*
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* Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
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*
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* Derived from drivers/char/hw_random/omap-rng.c
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* Copyright 2005 (c) MontaVista Software, Inc.
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* Author: Deepak Saxena <dsaxena@plexity.net>
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*
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* Overview:
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* This driver is useful for platforms that have an IO range that provides
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* periodic random data from a single IO memory address. All the platform
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* has to do is provide the address and 'wait time' that new data becomes
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* available.
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*
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* TODO: add support for reading sizes other than 32bits and masking
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*/
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#include <linux/completion.h>
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#include <linux/delay.h>
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#include <linux/hrtimer.h>
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#include <linux/hw_random.h>
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#include <linux/io.h>
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#include <linux/ktime.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#include <linux/time.h>
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#include <linux/timeriomem-rng.h>
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struct timeriomem_rng_private {
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void __iomem *io_base;
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ktime_t period;
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unsigned int present:1;
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struct hrtimer timer;
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struct completion completion;
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struct hwrng rng_ops;
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};
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static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
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size_t max, bool wait)
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{
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struct timeriomem_rng_private *priv =
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container_of(hwrng, struct timeriomem_rng_private, rng_ops);
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int retval = 0;
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int period_us = ktime_to_us(priv->period);
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/*
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* There may not have been enough time for new data to be generated
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* since the last request. If the caller doesn't want to wait, let them
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* bail out. Otherwise, wait for the completion. If the new data has
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* already been generated, the completion should already be available.
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*/
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if (!wait && !priv->present)
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return 0;
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wait_for_completion(&priv->completion);
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do {
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/*
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* After the first read, all additional reads will need to wait
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* for the RNG to generate new data. Since the period can have
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* a wide range of values (1us to 1s have been observed), allow
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* for 1% tolerance in the sleep time rather than a fixed value.
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*/
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if (retval > 0)
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usleep_range(period_us,
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period_us + min(1, period_us / 100));
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*(u32 *)data = readl(priv->io_base);
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retval += sizeof(u32);
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data += sizeof(u32);
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max -= sizeof(u32);
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} while (wait && max > sizeof(u32));
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/*
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* Block any new callers until the RNG has had time to generate new
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* data.
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*/
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priv->present = 0;
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reinit_completion(&priv->completion);
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hrtimer_forward_now(&priv->timer, priv->period);
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hrtimer_restart(&priv->timer);
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return retval;
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}
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static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
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{
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struct timeriomem_rng_private *priv
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= container_of(timer, struct timeriomem_rng_private, timer);
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priv->present = 1;
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complete(&priv->completion);
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return HRTIMER_NORESTART;
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}
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static int timeriomem_rng_probe(struct platform_device *pdev)
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{
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struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
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struct timeriomem_rng_private *priv;
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struct resource *res;
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int err = 0;
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int period;
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if (!pdev->dev.of_node && !pdata) {
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dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
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return -EINVAL;
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}
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (!res)
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return -ENXIO;
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if (res->start % 4 != 0 || resource_size(res) != 4) {
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dev_err(&pdev->dev,
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"address must be four bytes wide and aligned\n");
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return -EINVAL;
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}
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/* Allocate memory for the device structure (and zero it) */
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priv = devm_kzalloc(&pdev->dev,
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sizeof(struct timeriomem_rng_private), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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platform_set_drvdata(pdev, priv);
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if (pdev->dev.of_node) {
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int i;
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if (!of_property_read_u32(pdev->dev.of_node,
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"period", &i))
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period = i;
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else {
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dev_err(&pdev->dev, "missing period\n");
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return -EINVAL;
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}
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if (!of_property_read_u32(pdev->dev.of_node,
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"quality", &i))
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priv->rng_ops.quality = i;
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else
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priv->rng_ops.quality = 0;
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} else {
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period = pdata->period;
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priv->rng_ops.quality = pdata->quality;
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}
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priv->period = ns_to_ktime(period * NSEC_PER_USEC);
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init_completion(&priv->completion);
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hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
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priv->timer.function = timeriomem_rng_trigger;
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priv->rng_ops.name = dev_name(&pdev->dev);
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priv->rng_ops.read = timeriomem_rng_read;
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priv->io_base = devm_ioremap_resource(&pdev->dev, res);
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if (IS_ERR(priv->io_base)) {
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return PTR_ERR(priv->io_base);
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}
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/* Assume random data is already available. */
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priv->present = 1;
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complete(&priv->completion);
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err = hwrng_register(&priv->rng_ops);
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if (err) {
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dev_err(&pdev->dev, "problem registering\n");
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return err;
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}
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dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
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priv->io_base, period);
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return 0;
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}
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static int timeriomem_rng_remove(struct platform_device *pdev)
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{
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struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
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hwrng_unregister(&priv->rng_ops);
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hrtimer_cancel(&priv->timer);
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return 0;
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}
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static const struct of_device_id timeriomem_rng_match[] = {
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{ .compatible = "timeriomem_rng" },
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{},
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};
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MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
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static struct platform_driver timeriomem_rng_driver = {
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.driver = {
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.name = "timeriomem_rng",
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.of_match_table = timeriomem_rng_match,
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},
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.probe = timeriomem_rng_probe,
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.remove = timeriomem_rng_remove,
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};
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module_platform_driver(timeriomem_rng_driver);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
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MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
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