diff options
Diffstat (limited to 'drivers/char/hw_random/tx4939-rng.c')
| -rw-r--r-- | drivers/char/hw_random/tx4939-rng.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/drivers/char/hw_random/tx4939-rng.c b/drivers/char/hw_random/tx4939-rng.c new file mode 100644 index 000000000..a7b694913 --- /dev/null +++ b/drivers/char/hw_random/tx4939-rng.c @@ -0,0 +1,168 @@ +/* + * RNG driver for TX4939 Random Number Generators (RNG) + * + * Copyright (C) 2009 Atsushi Nemoto <anemo@mba.ocn.ne.jp> + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + */ +#include <linux/err.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/io.h> +#include <linux/platform_device.h> +#include <linux/hw_random.h> +#include <linux/gfp.h> + +#define TX4939_RNG_RCSR 0x00000000 +#define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8) + +#define TX4939_RNG_RCSR_INTE 0x00000008 +#define TX4939_RNG_RCSR_RST 0x00000004 +#define TX4939_RNG_RCSR_FIN 0x00000002 +#define TX4939_RNG_RCSR_ST 0x00000001 + +struct tx4939_rng { + struct hwrng rng; + void __iomem *base; + u64 databuf[3]; + unsigned int data_avail; +}; + +static void rng_io_start(void) +{ +#ifndef CONFIG_64BIT + /* + * readq is reading a 64-bit register using a 64-bit load. On + * a 32-bit kernel however interrupts or any other processor + * exception would clobber the upper 32-bit of the processor + * register so interrupts need to be disabled. + */ + local_irq_disable(); +#endif +} + +static void rng_io_end(void) +{ +#ifndef CONFIG_64BIT + local_irq_enable(); +#endif +} + +static u64 read_rng(void __iomem *base, unsigned int offset) +{ + return ____raw_readq(base + offset); +} + +static void write_rng(u64 val, void __iomem *base, unsigned int offset) +{ + return ____raw_writeq(val, base + offset); +} + +static int tx4939_rng_data_present(struct hwrng *rng, int wait) +{ + struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); + int i; + + if (rngdev->data_avail) + return rngdev->data_avail; + for (i = 0; i < 20; i++) { + rng_io_start(); + if (!(read_rng(rngdev->base, TX4939_RNG_RCSR) + & TX4939_RNG_RCSR_ST)) { + rngdev->databuf[0] = + read_rng(rngdev->base, TX4939_RNG_ROR(0)); + rngdev->databuf[1] = + read_rng(rngdev->base, TX4939_RNG_ROR(1)); + rngdev->databuf[2] = + read_rng(rngdev->base, TX4939_RNG_ROR(2)); + rngdev->data_avail = + sizeof(rngdev->databuf) / sizeof(u32); + /* Start RNG */ + write_rng(TX4939_RNG_RCSR_ST, + rngdev->base, TX4939_RNG_RCSR); + wait = 0; + } + rng_io_end(); + if (!wait) + break; + /* 90 bus clock cycles by default for generation */ + ndelay(90 * 5); + } + return rngdev->data_avail; +} + +static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer) +{ + struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); + + rngdev->data_avail--; + *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail); + return sizeof(u32); +} + +static int __init tx4939_rng_probe(struct platform_device *dev) +{ + struct tx4939_rng *rngdev; + struct resource *r; + int i; + + rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL); + if (!rngdev) + return -ENOMEM; + r = platform_get_resource(dev, IORESOURCE_MEM, 0); + rngdev->base = devm_ioremap_resource(&dev->dev, r); + if (IS_ERR(rngdev->base)) + return PTR_ERR(rngdev->base); + + rngdev->rng.name = dev_name(&dev->dev); + rngdev->rng.data_present = tx4939_rng_data_present; + rngdev->rng.data_read = tx4939_rng_data_read; + + rng_io_start(); + /* Reset RNG */ + write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR); + write_rng(0, rngdev->base, TX4939_RNG_RCSR); + /* Start RNG */ + write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR); + rng_io_end(); + /* + * Drop first two results. From the datasheet: + * The quality of the random numbers generated immediately + * after reset can be insufficient. Therefore, do not use + * random numbers obtained from the first and second + * generations; use the ones from the third or subsequent + * generation. + */ + for (i = 0; i < 2; i++) { + rngdev->data_avail = 0; + if (!tx4939_rng_data_present(&rngdev->rng, 1)) + return -EIO; + } + + platform_set_drvdata(dev, rngdev); + return hwrng_register(&rngdev->rng); +} + +static int __exit tx4939_rng_remove(struct platform_device *dev) +{ + struct tx4939_rng *rngdev = platform_get_drvdata(dev); + + hwrng_unregister(&rngdev->rng); + return 0; +} + +static struct platform_driver tx4939_rng_driver = { + .driver = { + .name = "tx4939-rng", + }, + .remove = tx4939_rng_remove, +}; + +module_platform_driver_probe(tx4939_rng_driver, tx4939_rng_probe); + +MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); +MODULE_LICENSE("GPL"); |