linux/drivers/char/hw_random/atmel-rng.c

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/*
* Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/hw_random.h>
#include <linux/platform_device.h>
#define TRNG_CR 0x00
#define TRNG_ISR 0x1c
#define TRNG_ODATA 0x50
#define TRNG_KEY 0x524e4700 /* RNG */
struct atmel_trng {
struct clk *clk;
void __iomem *base;
struct hwrng rng;
};
static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
bool wait)
{
struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
u32 *data = buf;
/* data ready? */
if (readl(trng->base + TRNG_ODATA) & 1) {
*data = readl(trng->base + TRNG_ODATA);
hwrng: atmel-rng - fix race condition leading to repeated bits Data valid gets cleared by reading the ISR (status register) and NOT from reading ODATA (data register). A new data word can become available between checking ISR and reading ODATA, causing us to reuse the same data word next time atmel_trng_read() gets called, if that happens before the following data word is ready. With this fixed, rngtest no longer complains of 'Continous run' errors. Before: rngtest -c 1000 < /dev/hwrng rngtest 3 Copyright (c) 2004 by Henrique de Moraes Holschuh This is free software; see the source for copying conditions. There is NO warr. rngtest: starting FIPS tests... rngtest: bits received from input: 20000032 rngtest: FIPS 140-2 successes: 923 rngtest: FIPS 140-2 failures: 77 rngtest: FIPS 140-2(2001-10-10) Monobit: 0 rngtest: FIPS 140-2(2001-10-10) Poker: 0 rngtest: FIPS 140-2(2001-10-10) Runs: 1 rngtest: FIPS 140-2(2001-10-10) Long run: 0 rngtest: FIPS 140-2(2001-10-10) Continuous run: 76 rngtest: input channel speed: (min=721.402; avg=46003.510; max=49321.338)Kibitss rngtest: FIPS tests speed: (min=11.442; avg=12.714; max=12.801)Mibits/s rngtest: Program run time: 1931860 microseconds After: rngtest -c 1000 < /dev/hwrng rngtest 3 Copyright (c) 2004 by Henrique de Moraes Holschuh This is free software; see the source for copying conditions. There is NO warr. rngtest: starting FIPS tests... rngtest: bits received from input: 20000032 rngtest: FIPS 140-2 successes: 1000 rngtest: FIPS 140-2 failures: 0 rngtest: FIPS 140-2(2001-10-10) Monobit: 0 rngtest: FIPS 140-2(2001-10-10) Poker: 0 rngtest: FIPS 140-2(2001-10-10) Runs: 0 rngtest: FIPS 140-2(2001-10-10) Long run: 0 rngtest: FIPS 140-2(2001-10-10) Continuous run: 0 rngtest: input channel speed: (min=777.518; avg=36988.482; max=43115.342)Kibitss rngtest: FIPS tests speed: (min=11.951; avg=12.715; max=12.887)Mibits/s rngtest: Program run time: 2035543 microseconds Cc: stable@vger.kernel.org Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk> Reported-by: George Pontis <GPontis@z9.com> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2012-05-31 10:53:08 +00:00
/*
ensure data ready is only set again AFTER the next data
word is ready in case it got set between checking ISR
and reading ODATA, so we don't risk re-reading the
same word
*/
readl(trng->base + TRNG_ISR);
return 4;
} else
return 0;
}
static int atmel_trng_probe(struct platform_device *pdev)
{
struct atmel_trng *trng;
struct resource *res;
int ret;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -EINVAL;
trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
if (!trng)
return -ENOMEM;
if (!devm_request_mem_region(&pdev->dev, res->start,
resource_size(res), pdev->name))
return -EBUSY;
trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
if (!trng->base)
return -EBUSY;
trng->clk = clk_get(&pdev->dev, NULL);
if (IS_ERR(trng->clk))
return PTR_ERR(trng->clk);
ret = clk_enable(trng->clk);
if (ret)
goto err_enable;
writel(TRNG_KEY | 1, trng->base + TRNG_CR);
trng->rng.name = pdev->name;
trng->rng.read = atmel_trng_read;
ret = hwrng_register(&trng->rng);
if (ret)
goto err_register;
platform_set_drvdata(pdev, trng);
return 0;
err_register:
clk_disable(trng->clk);
err_enable:
clk_put(trng->clk);
return ret;
}
static int __devexit atmel_trng_remove(struct platform_device *pdev)
{
struct atmel_trng *trng = platform_get_drvdata(pdev);
hwrng_unregister(&trng->rng);
writel(TRNG_KEY, trng->base + TRNG_CR);
clk_disable(trng->clk);
clk_put(trng->clk);
platform_set_drvdata(pdev, NULL);
return 0;
}
#ifdef CONFIG_PM
static int atmel_trng_suspend(struct device *dev)
{
struct atmel_trng *trng = dev_get_drvdata(dev);
clk_disable(trng->clk);
return 0;
}
static int atmel_trng_resume(struct device *dev)
{
struct atmel_trng *trng = dev_get_drvdata(dev);
return clk_enable(trng->clk);
}
static const struct dev_pm_ops atmel_trng_pm_ops = {
.suspend = atmel_trng_suspend,
.resume = atmel_trng_resume,
};
#endif /* CONFIG_PM */
static struct platform_driver atmel_trng_driver = {
.probe = atmel_trng_probe,
.remove = __devexit_p(atmel_trng_remove),
.driver = {
.name = "atmel-trng",
.owner = THIS_MODULE,
#ifdef CONFIG_PM
.pm = &atmel_trng_pm_ops,
#endif /* CONFIG_PM */
},
};
module_platform_driver(atmel_trng_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
MODULE_DESCRIPTION("Atmel true random number generator driver");