MIPS: hwrng: Add TX4939 RNG driver

This patch adds support for the integrated RNG of the TX4939 SoC.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 184 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 00000000000..544d9085a8e
--- /dev/null
+++ b/drivers/char/hw_random/tx4939-rng.c
@@ -0,0 +1,184 @@
+/*
+ * 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/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>
+
+#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;
+
+	r = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (!r)
+		return -EBUSY;
+	rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
+	if (!rngdev)
+		return -ENOMEM;
+	if (!devm_request_mem_region(&dev->dev, r->start, resource_size(r),
+				     dev_name(&dev->dev)))
+		return -EBUSY;
+	rngdev->base = devm_ioremap(&dev->dev, r->start, resource_size(r));
+	if (!rngdev->base)
+		return -EBUSY;
+
+	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);
+	platform_set_drvdata(dev, NULL);
+	return 0;
+}
+
+static struct platform_driver tx4939_rng_driver = {
+	.driver		= {
+		.name	= "tx4939-rng",
+		.owner	= THIS_MODULE,
+	},
+	.remove = tx4939_rng_remove,
+};
+
+static int __init tx4939rng_init(void)
+{
+	return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe);
+}
+
+static void __exit tx4939rng_exit(void)
+{
+	platform_driver_unregister(&tx4939_rng_driver);
+}
+
+module_init(tx4939rng_init);
+module_exit(tx4939rng_exit);
+
+MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
+MODULE_LICENSE("GPL");