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>

3 files changed, 198 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f4b3f7293feb..ce66a70184f7 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -149,6 +149,19 @@ config HW_RANDOM_VIRTIO
           To compile this driver as a module, choose M here: the
           module will be called virtio-rng.  If unsure, say N.
 
+config HW_RANDOM_TX4939
+        tristate "TX4939 Random Number Generator support"
+        depends on HW_RANDOM && SOC_TX4939
+        default HW_RANDOM
+        ---help---
+          This driver provides kernel-side support for the Random Number
+          Generator hardware found on TX4939 SoC.
+
+          To compile this driver as a module, choose M here: the
+          module will be called tx4939-rng.
+
+          If unsure, say Y.
+
 config HW_RANDOM_MXC_RNGA
         tristate "Freescale i.MX RNGA Random Number Generator"
         depends on HW_RANDOM && ARCH_HAS_RNGA
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index fd1ecd2f6731..676828ba8123 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -15,4 +15,5 @@ obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
 obj-$(CONFIG_HW_RANDOM_PASEMI) += pasemi-rng.o
 obj-$(CONFIG_HW_RANDOM_VIRTIO) += virtio-rng.o
+obj-$(CONFIG_HW_RANDOM_TX4939) += tx4939-rng.o
 obj-$(CONFIG_HW_RANDOM_MXC_RNGA) += mxc-rnga.o
diff --git a/drivers/char/hw_random/tx4939-rng.c b/drivers/char/hw_random/tx4939-rng.c
new file mode 100644
index 000000000000..544d9085a8e8
--- /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");