diff options
Diffstat (limited to 'drivers/char/hw_random/picoxcell-rng.c')
| -rw-r--r-- | drivers/char/hw_random/picoxcell-rng.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/drivers/char/hw_random/picoxcell-rng.c b/drivers/char/hw_random/picoxcell-rng.c new file mode 100644 index 00000000000..990d55a5e3e --- /dev/null +++ b/drivers/char/hw_random/picoxcell-rng.c @@ -0,0 +1,208 @@ +/* + * Copyright (c) 2010-2011 Picochip Ltd., Jamie Iles + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * All enquiries to support@picochip.com + */ +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/hw_random.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/platform_device.h> + +#define DATA_REG_OFFSET 0x0200 +#define CSR_REG_OFFSET 0x0278 +#define CSR_OUT_EMPTY_MASK (1 << 24) +#define CSR_FAULT_MASK (1 << 1) +#define TRNG_BLOCK_RESET_MASK (1 << 0) +#define TAI_REG_OFFSET 0x0380 + +/* + * The maximum amount of time in microseconds to spend waiting for data if the + * core wants us to wait. The TRNG should generate 32 bits every 320ns so a + * timeout of 20us seems reasonable. The TRNG does builtin tests of the data + * for randomness so we can't always assume there is data present. + */ +#define PICO_TRNG_TIMEOUT 20 + +static void __iomem *rng_base; +static struct clk *rng_clk; +struct device *rng_dev; + +static inline u32 picoxcell_trng_read_csr(void) +{ + return __raw_readl(rng_base + CSR_REG_OFFSET); +} + +static inline bool picoxcell_trng_is_empty(void) +{ + return picoxcell_trng_read_csr() & CSR_OUT_EMPTY_MASK; +} + +/* + * Take the random number generator out of reset and make sure the interrupts + * are masked. We shouldn't need to get large amounts of random bytes so just + * poll the status register. The hardware generates 32 bits every 320ns so we + * shouldn't have to wait long enough to warrant waiting for an IRQ. + */ +static void picoxcell_trng_start(void) +{ + __raw_writel(0, rng_base + TAI_REG_OFFSET); + __raw_writel(0, rng_base + CSR_REG_OFFSET); +} + +static void picoxcell_trng_reset(void) +{ + __raw_writel(TRNG_BLOCK_RESET_MASK, rng_base + CSR_REG_OFFSET); + __raw_writel(TRNG_BLOCK_RESET_MASK, rng_base + TAI_REG_OFFSET); + picoxcell_trng_start(); +} + +/* + * Get some random data from the random number generator. The hw_random core + * layer provides us with locking. + */ +static int picoxcell_trng_read(struct hwrng *rng, void *buf, size_t max, + bool wait) +{ + int i; + + /* Wait for some data to become available. */ + for (i = 0; i < PICO_TRNG_TIMEOUT && picoxcell_trng_is_empty(); ++i) { + if (!wait) + return 0; + + udelay(1); + } + + if (picoxcell_trng_read_csr() & CSR_FAULT_MASK) { + dev_err(rng_dev, "fault detected, resetting TRNG\n"); + picoxcell_trng_reset(); + return -EIO; + } + + if (i == PICO_TRNG_TIMEOUT) + return 0; + + *(u32 *)buf = __raw_readl(rng_base + DATA_REG_OFFSET); + return sizeof(u32); +} + +static struct hwrng picoxcell_trng = { + .name = "picoxcell", + .read = picoxcell_trng_read, +}; + +static int picoxcell_trng_probe(struct platform_device *pdev) +{ + int ret; + struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); + + if (!mem) { + dev_warn(&pdev->dev, "no memory resource\n"); + return -ENOMEM; + } + + if (!devm_request_mem_region(&pdev->dev, mem->start, resource_size(mem), + "picoxcell_trng")) { + dev_warn(&pdev->dev, "unable to request io mem\n"); + return -EBUSY; + } + + rng_base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem)); + if (!rng_base) { + dev_warn(&pdev->dev, "unable to remap io mem\n"); + return -ENOMEM; + } + + rng_clk = clk_get(&pdev->dev, NULL); + if (IS_ERR(rng_clk)) { + dev_warn(&pdev->dev, "no clk\n"); + return PTR_ERR(rng_clk); + } + + ret = clk_enable(rng_clk); + if (ret) { + dev_warn(&pdev->dev, "unable to enable clk\n"); + goto err_enable; + } + + picoxcell_trng_start(); + ret = hwrng_register(&picoxcell_trng); + if (ret) + goto err_register; + + rng_dev = &pdev->dev; + dev_info(&pdev->dev, "pixoxcell random number generator active\n"); + + return 0; + +err_register: + clk_disable(rng_clk); +err_enable: + clk_put(rng_clk); + + return ret; +} + +static int __devexit picoxcell_trng_remove(struct platform_device *pdev) +{ + hwrng_unregister(&picoxcell_trng); + clk_disable(rng_clk); + clk_put(rng_clk); + + return 0; +} + +#ifdef CONFIG_PM +static int picoxcell_trng_suspend(struct device *dev) +{ + clk_disable(rng_clk); + + return 0; +} + +static int picoxcell_trng_resume(struct device *dev) +{ + return clk_enable(rng_clk); +} + +static const struct dev_pm_ops picoxcell_trng_pm_ops = { + .suspend = picoxcell_trng_suspend, + .resume = picoxcell_trng_resume, +}; +#endif /* CONFIG_PM */ + +static struct platform_driver picoxcell_trng_driver = { + .probe = picoxcell_trng_probe, + .remove = __devexit_p(picoxcell_trng_remove), + .driver = { + .name = "picoxcell-trng", + .owner = THIS_MODULE, +#ifdef CONFIG_PM + .pm = &picoxcell_trng_pm_ops, +#endif /* CONFIG_PM */ + }, +}; + +static int __init picoxcell_trng_init(void) +{ + return platform_driver_register(&picoxcell_trng_driver); +} +module_init(picoxcell_trng_init); + +static void __exit picoxcell_trng_exit(void) +{ + platform_driver_unregister(&picoxcell_trng_driver); +} +module_exit(picoxcell_trng_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Jamie Iles"); +MODULE_DESCRIPTION("Picochip picoXcell TRNG driver"); |