diff options
Diffstat (limited to 'arch/powerpc/platforms/powernv/rng.c')
| -rw-r--r-- | arch/powerpc/platforms/powernv/rng.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c new file mode 100644 index 000000000..196aa70fe --- /dev/null +++ b/arch/powerpc/platforms/powernv/rng.c @@ -0,0 +1,200 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright 2013, Michael Ellerman, IBM Corporation. + */ + +#define pr_fmt(fmt) "powernv-rng: " fmt + +#include <linux/kernel.h> +#include <linux/of.h> +#include <linux/of_address.h> +#include <linux/of_platform.h> +#include <linux/slab.h> +#include <linux/smp.h> +#include <asm/archrandom.h> +#include <asm/cputable.h> +#include <asm/io.h> +#include <asm/prom.h> +#include <asm/machdep.h> +#include <asm/smp.h> +#include "powernv.h" + +#define DARN_ERR 0xFFFFFFFFFFFFFFFFul + +struct pnv_rng { + void __iomem *regs; + void __iomem *regs_real; + unsigned long mask; +}; + +static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng); + +static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) +{ + unsigned long parity; + + /* Calculate the parity of the value */ + asm (".machine push; \ + .machine power7; \ + popcntd %0,%1; \ + .machine pop;" + : "=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; +} + +static int pnv_get_random_darn(unsigned long *v) +{ + unsigned long val; + + /* Using DARN with L=1 - 64-bit conditioned random number */ + asm volatile(PPC_DARN(%0, 1) : "=r"(val)); + + if (val == DARN_ERR) + return 0; + + *v = val; + + return 1; +} + +static int __init initialise_darn(void) +{ + unsigned long val; + int i; + + if (!cpu_has_feature(CPU_FTR_ARCH_300)) + return -ENODEV; + + for (i = 0; i < 10; i++) { + if (pnv_get_random_darn(&val)) { + ppc_md.get_random_seed = pnv_get_random_darn; + return 0; + } + } + return -EIO; +} + +int pnv_get_random_long(unsigned long *v) +{ + struct pnv_rng *rng; + + if (mfmsr() & MSR_DR) { + rng = get_cpu_var(pnv_rng); + *v = rng_whiten(rng, in_be64(rng->regs)); + put_cpu_var(rng); + } else { + rng = raw_cpu_read(pnv_rng); + *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); + } + return 1; +} +EXPORT_SYMBOL_GPL(pnv_get_random_long); + +static __init void rng_init_per_cpu(struct pnv_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 %pOF.\n", dn); + + for_each_possible_cpu(cpu) { + if (per_cpu(pnv_rng, cpu) == NULL || + cpu_to_chip_id(cpu) == chip_id) { + per_cpu(pnv_rng, cpu) = rng; + } + } +} + +static __init int rng_create(struct device_node *dn) +{ + struct pnv_rng *rng; + struct resource res; + unsigned long val; + + rng = kzalloc(sizeof(*rng), GFP_KERNEL); + if (!rng) + return -ENOMEM; + + if (of_address_to_resource(dn, 0, &res)) { + kfree(rng); + return -ENXIO; + } + + rng->regs_real = (void __iomem *)res.start; + + 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); + + ppc_md.get_random_seed = pnv_get_random_long; + + return 0; +} + +static int __init pnv_get_random_long_early(unsigned long *v) +{ + struct device_node *dn; + + if (!slab_is_available()) + return 0; + + if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early, + NULL) != pnv_get_random_long_early) + return 0; + + for_each_compatible_node(dn, NULL, "ibm,power-rng") + rng_create(dn); + + if (!ppc_md.get_random_seed) + return 0; + return ppc_md.get_random_seed(v); +} + +void __init pnv_rng_init(void) +{ + struct device_node *dn; + + /* Prefer darn over the rest. */ + if (!initialise_darn()) + return; + + dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng"); + if (dn) + ppc_md.get_random_seed = pnv_get_random_long_early; + + of_node_put(dn); +} + +static int __init pnv_rng_late_init(void) +{ + struct device_node *dn; + unsigned long v; + + /* In case it wasn't called during init for some other reason. */ + if (ppc_md.get_random_seed == pnv_get_random_long_early) + pnv_get_random_long_early(&v); + + if (ppc_md.get_random_seed == pnv_get_random_long) { + for_each_compatible_node(dn, NULL, "ibm,power-rng") + of_platform_device_create(dn, NULL, NULL); + } + + return 0; +} +machine_subsys_initcall(powernv, pnv_rng_late_init); |