1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright 2013, Michael Ellerman, IBM Corporation.
6 #define pr_fmt(fmt) "powernv-rng: " fmt
8 #include <linux/kernel.h>
10 #include <linux/of_address.h>
11 #include <linux/of_platform.h>
12 #include <linux/slab.h>
13 #include <linux/smp.h>
14 #include <asm/archrandom.h>
15 #include <asm/cputable.h>
18 #include <asm/machdep.h>
22 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
26 void __iomem *regs_real;
30 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
32 int powernv_hwrng_present(void)
34 struct powernv_rng *rng;
36 rng = get_cpu_var(powernv_rng);
41 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
45 /* Calculate the parity of the value */
46 asm (".machine push; \
50 : "=r" (parity) : "r" (val));
52 /* xor our value with the previous mask */
55 /* update the mask based on the parity of this value */
56 rng->mask = (rng->mask << 1) | (parity & 1);
61 int powernv_get_random_real_mode(unsigned long *v)
63 struct powernv_rng *rng;
65 rng = raw_cpu_read(powernv_rng);
67 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
72 static int powernv_get_random_darn(unsigned long *v)
76 /* Using DARN with L=1 - 64-bit conditioned random number */
77 asm volatile(PPC_DARN(%0, 1) : "=r"(val));
87 static int __init initialise_darn(void)
92 if (!cpu_has_feature(CPU_FTR_ARCH_300))
95 for (i = 0; i < 10; i++) {
96 if (powernv_get_random_darn(&val)) {
97 ppc_md.get_random_seed = powernv_get_random_darn;
104 int powernv_get_random_long(unsigned long *v)
106 struct powernv_rng *rng;
108 rng = get_cpu_var(powernv_rng);
110 *v = rng_whiten(rng, in_be64(rng->regs));
116 EXPORT_SYMBOL_GPL(powernv_get_random_long);
118 static __init void rng_init_per_cpu(struct powernv_rng *rng,
119 struct device_node *dn)
123 chip_id = of_get_ibm_chip_id(dn);
125 pr_warn("No ibm,chip-id found for %pOF.\n", dn);
127 for_each_possible_cpu(cpu) {
128 if (per_cpu(powernv_rng, cpu) == NULL ||
129 cpu_to_chip_id(cpu) == chip_id) {
130 per_cpu(powernv_rng, cpu) = rng;
135 static __init int rng_create(struct device_node *dn)
137 struct powernv_rng *rng;
141 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
145 if (of_address_to_resource(dn, 0, &res)) {
150 rng->regs_real = (void __iomem *)res.start;
152 rng->regs = of_iomap(dn, 0);
158 val = in_be64(rng->regs);
161 rng_init_per_cpu(rng, dn);
163 ppc_md.get_random_seed = powernv_get_random_long;
168 static int __init pnv_get_random_long_early(unsigned long *v)
170 struct device_node *dn;
172 if (!slab_is_available())
175 if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early,
176 NULL) != pnv_get_random_long_early)
179 for_each_compatible_node(dn, NULL, "ibm,power-rng")
182 if (!ppc_md.get_random_seed)
184 return ppc_md.get_random_seed(v);
187 void __init pnv_rng_init(void)
189 struct device_node *dn;
191 /* Prefer darn over the rest. */
192 if (!initialise_darn())
195 dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
197 ppc_md.get_random_seed = pnv_get_random_long_early;
202 static int __init pnv_rng_late_init(void)
204 struct device_node *dn;
207 /* In case it wasn't called during init for some other reason. */
208 if (ppc_md.get_random_seed == pnv_get_random_long_early)
209 pnv_get_random_long_early(&v);
211 if (ppc_md.get_random_seed == powernv_get_random_long) {
212 for_each_compatible_node(dn, NULL, "ibm,power-rng")
213 of_platform_device_create(dn, NULL, NULL);
218 machine_subsys_initcall(powernv, pnv_rng_late_init);