hwrng: Add a driver for the hwrng found in power7+ systems

Add a driver for the hwrng found in power7+ systems, based on the
existing code for the arch_get_random_long() hook.

We only register a single instance of the driver, not one per device,
because we use the existing per_cpu array of devices in the arch code.
This means we always read from the "closest" device, avoiding inter-chip
memory traffic.

Signed-off-by: Guo Chao <yan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 95 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 0aa9d91daef5..c206de2951f2 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -290,6 +290,19 @@ config HW_RANDOM_PSERIES
 
           If unsure, say Y.
 
+config HW_RANDOM_POWERNV
+        tristate "PowerNV Random Number Generator support"
+        depends on HW_RANDOM && PPC_POWERNV
+        default HW_RANDOM
+        ---help---
+          This is the driver for Random Number Generator hardware found
+          in POWER7+ and above machines for PowerNV platform.
+
+          To compile this driver as a module, choose M here: the
+          module will be called powernv-rng.
+
+          If unsure, say Y.
+
 config HW_RANDOM_EXYNOS
         tristate "EXYNOS HW random number generator support"
         depends on HW_RANDOM && HAS_IOMEM && HAVE_CLK
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index bed467c9300e..d7d2435ff7fa 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PICOXCELL) += picoxcell-rng.o
 obj-$(CONFIG_HW_RANDOM_PPC4XX) += ppc4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
+obj-$(CONFIG_HW_RANDOM_POWERNV) += powernv-rng.o
 obj-$(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/powernv-rng.c b/drivers/char/hw_random/powernv-rng.c
new file mode 100644
index 000000000000..3f4f63204560
--- /dev/null
+++ b/drivers/char/hw_random/powernv-rng.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/random.h>
+#include <linux/hw_random.h>
+
+static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+        unsigned long *buf;
+        int i, len;
+
+        /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
+        len = max / sizeof(unsigned long);
+
+        buf = (unsigned long *)data;
+
+        for (i = 0; i < len; i++)
+                powernv_get_random_long(buf++);
+
+        return len * sizeof(unsigned long);
+}
+
+static struct hwrng powernv_hwrng = {
+        .name = "powernv-rng",
+        .read = powernv_rng_read,
+};
+
+static int powernv_rng_remove(struct platform_device *pdev)
+{
+        hwrng_unregister(&powernv_hwrng);
+
+        return 0;
+}
+
+static int powernv_rng_probe(struct platform_device *pdev)
+{
+        int rc;
+
+        rc = hwrng_register(&powernv_hwrng);
+        if (rc) {
+                /* We only register one device, ignore any others */
+                if (rc == -EEXIST)
+                        rc = -ENODEV;
+
+                return rc;
+        }
+
+        pr_info("Registered powernv hwrng.\n");
+
+        return 0;
+}
+
+static struct of_device_id powernv_rng_match[] = {
+        { .compatible   = "ibm,power-rng",},
+        {},
+};
+MODULE_DEVICE_TABLE(of, powernv_rng_match);
+
+static struct platform_driver powernv_rng_driver = {
+        .driver = {
+                .name = "powernv_rng",
+                .of_match_table = powernv_rng_match,
+        },
+        .probe  = powernv_rng_probe,
+        .remove = powernv_rng_remove,
+};
+module_platform_driver(powernv_rng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");