diff options
Diffstat (limited to 'drivers/char/hw_random/pic32-rng.c')
| -rw-r--r-- | drivers/char/hw_random/pic32-rng.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/drivers/char/hw_random/pic32-rng.c b/drivers/char/hw_random/pic32-rng.c new file mode 100644 index 000000000..9b5e68a71 --- /dev/null +++ b/drivers/char/hw_random/pic32-rng.c @@ -0,0 +1,151 @@ +/* + * PIC32 RNG driver + * + * Joshua Henderson <joshua.henderson@microchip.com> + * Copyright (C) 2016 Microchip Technology Inc. All rights reserved. + * + * This program is free software; you can distribute it and/or modify it + * under the terms of the GNU General Public License (Version 2) as + * published by the Free Software Foundation. + * + * This program is distributed in the hope 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/clkdev.h> +#include <linux/err.h> +#include <linux/hw_random.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/platform_device.h> +#include <linux/slab.h> + +#define RNGCON 0x04 +#define TRNGEN BIT(8) +#define PRNGEN BIT(9) +#define PRNGCONT BIT(10) +#define TRNGMOD BIT(11) +#define SEEDLOAD BIT(12) +#define RNGPOLY1 0x08 +#define RNGPOLY2 0x0C +#define RNGNUMGEN1 0x10 +#define RNGNUMGEN2 0x14 +#define RNGSEED1 0x18 +#define RNGSEED2 0x1C +#define RNGRCNT 0x20 +#define RCNT_MASK 0x7F + +struct pic32_rng { + void __iomem *base; + struct hwrng rng; + struct clk *clk; +}; + +/* + * The TRNG can generate up to 24Mbps. This is a timeout that should be safe + * enough given the instructions in the loop and that the TRNG may not always + * be at maximum rate. + */ +#define RNG_TIMEOUT 500 + +static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max, + bool wait) +{ + struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng); + u64 *data = buf; + u32 t; + unsigned int timeout = RNG_TIMEOUT; + + do { + t = readl(priv->base + RNGRCNT) & RCNT_MASK; + if (t == 64) { + /* TRNG value comes through the seed registers */ + *data = ((u64)readl(priv->base + RNGSEED2) << 32) + + readl(priv->base + RNGSEED1); + return 8; + } + } while (wait && --timeout); + + return -EIO; +} + +static int pic32_rng_probe(struct platform_device *pdev) +{ + struct pic32_rng *priv; + struct resource *res; + u32 v; + int ret; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + priv->base = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(priv->base)) + return PTR_ERR(priv->base); + + priv->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(priv->clk)) + return PTR_ERR(priv->clk); + + ret = clk_prepare_enable(priv->clk); + if (ret) + return ret; + + /* enable TRNG in enhanced mode */ + v = TRNGEN | TRNGMOD; + writel(v, priv->base + RNGCON); + + priv->rng.name = pdev->name; + priv->rng.read = pic32_rng_read; + + ret = hwrng_register(&priv->rng); + if (ret) + goto err_register; + + platform_set_drvdata(pdev, priv); + + return 0; + +err_register: + clk_disable_unprepare(priv->clk); + return ret; +} + +static int pic32_rng_remove(struct platform_device *pdev) +{ + struct pic32_rng *rng = platform_get_drvdata(pdev); + + hwrng_unregister(&rng->rng); + writel(0, rng->base + RNGCON); + clk_disable_unprepare(rng->clk); + return 0; +} + +static const struct of_device_id pic32_rng_of_match[] = { + { .compatible = "microchip,pic32mzda-rng", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pic32_rng_of_match); + +static struct platform_driver pic32_rng_driver = { + .probe = pic32_rng_probe, + .remove = pic32_rng_remove, + .driver = { + .name = "pic32-rng", + .of_match_table = of_match_ptr(pic32_rng_of_match), + }, +}; + +module_platform_driver(pic32_rng_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>"); +MODULE_DESCRIPTION("Microchip PIC32 RNG Driver"); |