msm-rng.c
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/*
* Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
/* Device specific register offsets */
#define PRNG_DATA_OUT 0x0000
#define PRNG_STATUS 0x0004
#define PRNG_LFSR_CFG 0x0100
#define PRNG_CONFIG 0x0104
/* Device specific register masks and config values */
#define PRNG_LFSR_CFG_MASK 0x0000ffff
#define PRNG_LFSR_CFG_CLOCKS 0x0000dddd
#define PRNG_CONFIG_HW_ENABLE BIT(1)
#define PRNG_STATUS_DATA_AVAIL BIT(0)
#define MAX_HW_FIFO_DEPTH 16
#define MAX_HW_FIFO_SIZE (MAX_HW_FIFO_DEPTH * 4)
#define WORD_SZ 4
struct msm_rng {
void __iomem *base;
struct clk *clk;
struct hwrng hwrng;
};
#define to_msm_rng(p) container_of(p, struct msm_rng, hwrng)
static int msm_rng_enable(struct hwrng *hwrng, int enable)
{
struct msm_rng *rng = to_msm_rng(hwrng);
u32 val;
int ret;
ret = clk_prepare_enable(rng->clk);
if (ret)
return ret;
if (enable) {
/* Enable PRNG only if it is not already enabled */
val = readl_relaxed(rng->base + PRNG_CONFIG);
if (val & PRNG_CONFIG_HW_ENABLE)
goto already_enabled;
val = readl_relaxed(rng->base + PRNG_LFSR_CFG);
val &= ~PRNG_LFSR_CFG_MASK;
val |= PRNG_LFSR_CFG_CLOCKS;
writel(val, rng->base + PRNG_LFSR_CFG);
val = readl_relaxed(rng->base + PRNG_CONFIG);
val |= PRNG_CONFIG_HW_ENABLE;
writel(val, rng->base + PRNG_CONFIG);
} else {
val = readl_relaxed(rng->base + PRNG_CONFIG);
val &= ~PRNG_CONFIG_HW_ENABLE;
writel(val, rng->base + PRNG_CONFIG);
}
already_enabled:
clk_disable_unprepare(rng->clk);
return 0;
}
static int msm_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait)
{
struct msm_rng *rng = to_msm_rng(hwrng);
size_t currsize = 0;
u32 *retdata = data;
size_t maxsize;
int ret;
u32 val;
/* calculate max size bytes to transfer back to caller */
maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, max);
/* no room for word data */
if (maxsize < WORD_SZ)
return 0;
ret = clk_prepare_enable(rng->clk);
if (ret)
return ret;
/* read random data from hardware */
do {
val = readl_relaxed(rng->base + PRNG_STATUS);
if (!(val & PRNG_STATUS_DATA_AVAIL))
break;
val = readl_relaxed(rng->base + PRNG_DATA_OUT);
if (!val)
break;
*retdata++ = val;
currsize += WORD_SZ;
/* make sure we stay on 32bit boundary */
if ((maxsize - currsize) < WORD_SZ)
break;
} while (currsize < maxsize);
clk_disable_unprepare(rng->clk);
return currsize;
}
static int msm_rng_init(struct hwrng *hwrng)
{
return msm_rng_enable(hwrng, 1);
}
static void msm_rng_cleanup(struct hwrng *hwrng)
{
msm_rng_enable(hwrng, 0);
}
static int msm_rng_probe(struct platform_device *pdev)
{
struct resource *res;
struct msm_rng *rng;
int ret;
rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
if (!rng)
return -ENOMEM;
platform_set_drvdata(pdev, rng);
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
rng->base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(rng->base))
return PTR_ERR(rng->base);
rng->clk = devm_clk_get(&pdev->dev, "core");
if (IS_ERR(rng->clk))
return PTR_ERR(rng->clk);
rng->hwrng.name = KBUILD_MODNAME,
rng->hwrng.init = msm_rng_init,
rng->hwrng.cleanup = msm_rng_cleanup,
rng->hwrng.read = msm_rng_read,
ret = devm_hwrng_register(&pdev->dev, &rng->hwrng);
if (ret) {
dev_err(&pdev->dev, "failed to register hwrng\n");
return ret;
}
return 0;
}
static const struct of_device_id msm_rng_of_match[] = {
{ .compatible = "qcom,prng", },
{}
};
MODULE_DEVICE_TABLE(of, msm_rng_of_match);
static struct platform_driver msm_rng_driver = {
.probe = msm_rng_probe,
.driver = {
.name = KBUILD_MODNAME,
.of_match_table = of_match_ptr(msm_rng_of_match),
}
};
module_platform_driver(msm_rng_driver);
MODULE_ALIAS("platform:" KBUILD_MODNAME);
MODULE_AUTHOR("The Linux Foundation");
MODULE_DESCRIPTION("Qualcomm MSM random number generator driver");
MODULE_LICENSE("GPL v2");