powerpc: Implement arch_get_random_long/int() for powernv

[karo-tx-linux.git] / arch / powerpc / platforms / powernv / rng.c

diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
new file mode 100644 (file)
index 0000000..02db7d7
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright 2013, Michael Ellerman, IBM Corporation.
+ *
+ * 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)    "powernv-rng: " fmt
+
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <asm/archrandom.h>
+#include <asm/io.h>
+#include <asm/machdep.h>
+
+
+struct powernv_rng {
+       void __iomem *regs;
+       unsigned long mask;
+};
+
+static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
+
+
+static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
+{
+       unsigned long parity;
+
+       /* Calculate the parity of the value */
+       asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
+
+       /* xor our value with the previous mask */
+       val ^= rng->mask;
+
+       /* update the mask based on the parity of this value */
+       rng->mask = (rng->mask << 1) | (parity & 1);
+
+       return val;
+}
+
+int powernv_get_random_long(unsigned long *v)
+{
+       struct powernv_rng *rng;
+
+       rng = get_cpu_var(powernv_rng);
+
+       *v = rng_whiten(rng, in_be64(rng->regs));
+
+       put_cpu_var(rng);
+
+       return 1;
+}
+EXPORT_SYMBOL_GPL(powernv_get_random_long);
+
+static __init void rng_init_per_cpu(struct powernv_rng *rng,
+                                   struct device_node *dn)
+{
+       int chip_id, cpu;
+
+       chip_id = of_get_ibm_chip_id(dn);
+       if (chip_id == -1)
+               pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
+
+       for_each_possible_cpu(cpu) {
+               if (per_cpu(powernv_rng, cpu) == NULL ||
+                   cpu_to_chip_id(cpu) == chip_id) {
+                       per_cpu(powernv_rng, cpu) = rng;
+               }
+       }
+}
+
+static __init int rng_create(struct device_node *dn)
+{
+       struct powernv_rng *rng;
+       unsigned long val;
+
+       rng = kzalloc(sizeof(*rng), GFP_KERNEL);
+       if (!rng)
+               return -ENOMEM;
+
+       rng->regs = of_iomap(dn, 0);
+       if (!rng->regs) {
+               kfree(rng);
+               return -ENXIO;
+       }
+
+       val = in_be64(rng->regs);
+       rng->mask = val;
+
+       rng_init_per_cpu(rng, dn);
+
+       pr_info_once("Registering arch random hook.\n");
+
+       ppc_md.get_random_long = powernv_get_random_long;
+
+       return 0;
+}
+
+static __init int rng_init(void)
+{
+       struct device_node *dn;
+       int rc;
+
+       for_each_compatible_node(dn, NULL, "ibm,power-rng") {
+               rc = rng_create(dn);
+               if (rc) {
+                       pr_err("Failed creating rng for %s (%d).\n",
+                               dn->full_name, rc);
+                       continue;
+               }
+
+               /* Create devices for hwrng driver */
+               of_platform_device_create(dn, NULL, NULL);
+       }
+
+       return 0;
+}
+subsys_initcall(rng_init);