hwrng: bcm2835 - Add Broadcom BCM2835 RNG driver

This adds a driver for random number generator present on Broadcom BCM2835 SoC,
used in Raspberry Pi and Roku 2 devices.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: linux-rpi-kernel@lists.infradead.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 126 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index c5a0262251bc..2f9dbf7568fb 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -86,6 +86,18 @@ config HW_RANDOM_BCM63XX
 
           If unusure, say Y.
 
+config HW_RANDOM_BCM2835
+        tristate "Broadcom BCM2835 Random Number Generator support"
+        depends on HW_RANDOM && ARCH_BCM2835
+        default HW_RANDOM
+        ---help---
+          This driver provides kernel-side support for the Random Number
+          Generator hardware found on the Broadcom BCM2835 SoCs.
+
+          To compile this driver as a module, choose M here: the
+          module will be called bcm2835-rng
+
+          If unsure, say Y.
 
 config HW_RANDOM_GEODE
         tristate "AMD Geode HW Random Number Generator support"
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 1fd7eec9fbf6..bed467c9300e 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -26,3 +26,4 @@ obj-$(CONFIG_HW_RANDOM_PPC4XX) += ppc4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
 obj-$(CONFIG_HW_RANDOM_EXYNOS)  += exynos-rng.o
 obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
+obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
new file mode 100644
index 000000000000..eb7f14725ebd
--- /dev/null
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -0,0 +1,113 @@
+/**
+ * Copyright (c) 2010-2012 Broadcom. All rights reserved.
+ * Copyright (c) 2013 Lubomir Rintel
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License ("GPL")
+ * version 2, as published by the Free Software Foundation.
+ */
+
+#include <linux/hw_random.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+
+#define RNG_CTRL        0x0
+#define RNG_STATUS      0x4
+#define RNG_DATA        0x8
+
+/* enable rng */
+#define RNG_RBGEN       0x1
+
+/* the initial numbers generated are "less random" so will be discarded */
+#define RNG_WARMUP_COUNT 0x40000
+
+static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
+                               bool wait)
+{
+        void __iomem *rng_base = (void __iomem *)rng->priv;
+
+        while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
+                if (!wait)
+                        return 0;
+                cpu_relax();
+        }
+
+        *(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
+        return sizeof(u32);
+}
+
+static struct hwrng bcm2835_rng_ops = {
+        .name   = "bcm2835",
+        .read   = bcm2835_rng_read,
+};
+
+static int bcm2835_rng_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct device_node *np = dev->of_node;
+        void __iomem *rng_base;
+        int err;
+
+        /* map peripheral */
+        rng_base = of_iomap(np, 0);
+        if (!rng_base) {
+                dev_err(dev, "failed to remap rng regs");
+                return -ENODEV;
+        }
+        bcm2835_rng_ops.priv = (unsigned long)rng_base;
+
+        /* register driver */
+        err = hwrng_register(&bcm2835_rng_ops);
+        if (err) {
+                dev_err(dev, "hwrng registration failed\n");
+                iounmap(rng_base);
+        } else {
+                dev_info(dev, "hwrng registered\n");
+
+                /* set warm-up count & enable */
+                __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
+                __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
+        }
+        return err;
+}
+
+static int bcm2835_rng_remove(struct platform_device *pdev)
+{
+        void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
+
+        /* disable rng hardware */
+        __raw_writel(0, rng_base + RNG_CTRL);
+
+        /* unregister driver */
+        hwrng_unregister(&bcm2835_rng_ops);
+        iounmap(rng_base);
+
+        return 0;
+}
+
+static const struct of_device_id bcm2835_rng_of_match[] = {
+        { .compatible = "brcm,bcm2835-rng", },
+        {},
+};
+MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
+
+static struct platform_driver bcm2835_rng_driver = {
+        .driver = {
+                .name = "bcm2835-rng",
+                .owner = THIS_MODULE,
+                .of_match_table = bcm2835_rng_of_match,
+        },
+        .probe          = bcm2835_rng_probe,
+        .remove         = bcm2835_rng_remove,
+};
+module_platform_driver(bcm2835_rng_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
+MODULE_LICENSE("GPLv2");