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213 lines
5.4 KiB
213 lines
5.4 KiB
// 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 <[email protected]> |
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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 <[email protected]> |
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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 + max(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 at least four bytes wide and 32-bit 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 <[email protected]>"); |
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MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
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