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path: root/drivers/char/hw_random/nomadik-rng.c
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Diffstat (limited to 'drivers/char/hw_random/nomadik-rng.c')
-rw-r--r--drivers/char/hw_random/nomadik-rng.c103
1 files changed, 103 insertions, 0 deletions
diff --git a/drivers/char/hw_random/nomadik-rng.c b/drivers/char/hw_random/nomadik-rng.c
new file mode 100644
index 000000000000..a8b4c4010144
--- /dev/null
+++ b/drivers/char/hw_random/nomadik-rng.c
@@ -0,0 +1,103 @@
+/*
+ * Nomadik RNG support
+ * Copyright 2009 Alessandro Rubini
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/amba/bus.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+
+static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ void __iomem *base = (void __iomem *)rng->priv;
+
+ /*
+ * The register is 32 bits and gives 16 random bits (low half).
+ * A subsequent read will delay the core for 400ns, so we just read
+ * once and accept the very unlikely very small delay, even if wait==0.
+ */
+ *(u16 *)data = __raw_readl(base + 8) & 0xffff;
+ return 2;
+}
+
+/* we have at most one RNG per machine, granted */
+static struct hwrng nmk_rng = {
+ .name = "nomadik",
+ .read = nmk_rng_read,
+};
+
+static int nmk_rng_probe(struct amba_device *dev, struct amba_id *id)
+{
+ void __iomem *base;
+ int ret;
+
+ ret = amba_request_regions(dev, dev->dev.init_name);
+ if (ret)
+ return ret;
+ ret = -ENOMEM;
+ base = ioremap(dev->res.start, resource_size(&dev->res));
+ if (!base)
+ goto out_release;
+ nmk_rng.priv = (unsigned long)base;
+ ret = hwrng_register(&nmk_rng);
+ if (ret)
+ goto out_unmap;
+ return 0;
+
+out_unmap:
+ iounmap(base);
+out_release:
+ amba_release_regions(dev);
+ return ret;
+}
+
+static int nmk_rng_remove(struct amba_device *dev)
+{
+ void __iomem *base = (void __iomem *)nmk_rng.priv;
+ hwrng_unregister(&nmk_rng);
+ iounmap(base);
+ amba_release_regions(dev);
+ return 0;
+}
+
+static struct amba_id nmk_rng_ids[] = {
+ {
+ .id = 0x000805e1,
+ .mask = 0x000fffff, /* top bits are rev and cfg: accept all */
+ },
+ {0, 0},
+};
+
+static struct amba_driver nmk_rng_driver = {
+ .drv = {
+ .owner = THIS_MODULE,
+ .name = "rng",
+ },
+ .probe = nmk_rng_probe,
+ .remove = nmk_rng_remove,
+ .id_table = nmk_rng_ids,
+};
+
+static int __init nmk_rng_init(void)
+{
+ return amba_driver_register(&nmk_rng_driver);
+}
+
+static void __devexit nmk_rng_exit(void)
+{
+ amba_driver_unregister(&nmk_rng_driver);
+}
+
+module_init(nmk_rng_init);
+module_exit(nmk_rng_exit);
+
+MODULE_LICENSE("GPL");