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