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powerpc: Implement arch_get_random_long/int() for powernv
Add the plumbing to implement arch_get_random_long/int(). It didn't seem worth adding an extra ppc_md hook for int, so we reuse the one for long. Add an implementation for powernv based on the hwrng found in power7+ systems. We whiten the output of the hwrng, and the result passes all the dieharder tests. Signed-off-by: Michael Ellerman <[email protected]> Signed-off-by: Benjamin Herrenschmidt <[email protected]>
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‎arch/powerpc/Kconfig‎

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@@ -1012,6 +1012,9 @@ config PHYSICAL_START
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default "0x00000000"
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endif
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config ARCH_RANDOM
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def_bool n
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source "net/Kconfig"
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source "drivers/Kconfig"

‎arch/powerpc/include/asm/archrandom.h‎

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#ifndef _ASM_POWERPC_ARCHRANDOM_H
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#define _ASM_POWERPC_ARCHRANDOM_H
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#ifdef CONFIG_ARCH_RANDOM
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#include <asm/machdep.h>
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static inline int arch_get_random_long(unsigned long *v)
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{
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if (ppc_md.get_random_long)
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return ppc_md.get_random_long(v);
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return 0;
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}
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static inline int arch_get_random_int(unsigned int *v)
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{
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unsigned long val;
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int rc;
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rc = arch_get_random_long(&val);
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if (rc)
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*v = val;
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return rc;
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}
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int powernv_get_random_long(unsigned long *v);
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#endif /* CONFIG_ARCH_RANDOM */
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#endif /* _ASM_POWERPC_ARCHRANDOM_H */

‎arch/powerpc/include/asm/machdep.h‎

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@@ -263,6 +263,10 @@ struct machdep_calls {
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ssize_t (*cpu_probe)(const char *, size_t);
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ssize_t (*cpu_release)(const char *, size_t);
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#endif
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#ifdef CONFIG_ARCH_RANDOM
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int (*get_random_long)(unsigned long *v);
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#endif
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};
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extern void e500_idle(void);

‎arch/powerpc/platforms/powernv/Kconfig‎

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@@ -9,6 +9,7 @@ config PPC_POWERNV
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select EPAPR_BOOT
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select PPC_INDIRECT_PIO
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select PPC_UDBG_16550
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select ARCH_RANDOM
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default y
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config POWERNV_MSI

‎arch/powerpc/platforms/powernv/Makefile‎

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@@ -1,5 +1,5 @@
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obj-y += setup.o opal-takeover.o opal-wrappers.o opal.o
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obj-y += opal-rtc.o opal-nvram.o opal-lpc.o
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obj-y += opal-rtc.o opal-nvram.o opal-lpc.o rng.o
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obj-$(CONFIG_SMP) += smp.o
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obj-$(CONFIG_PCI) += pci.o pci-p5ioc2.o pci-ioda.o

‎arch/powerpc/platforms/powernv/rng.c‎

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/*
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* Copyright 2013, Michael Ellerman, IBM Corporation.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#define pr_fmt(fmt) "powernv-rng: " fmt
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#include <linux/kernel.h>
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#include <linux/of.h>
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#include <linux/of_platform.h>
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#include <linux/slab.h>
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#include <asm/archrandom.h>
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#include <asm/io.h>
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#include <asm/machdep.h>
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struct powernv_rng {
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void __iomem *regs;
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unsigned long mask;
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};
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static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
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static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
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{
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unsigned long parity;
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/* Calculate the parity of the value */
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asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
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/* xor our value with the previous mask */
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val ^= rng->mask;
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/* update the mask based on the parity of this value */
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rng->mask = (rng->mask << 1) | (parity & 1);
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return val;
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}
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int powernv_get_random_long(unsigned long *v)
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{
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struct powernv_rng *rng;
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rng = get_cpu_var(powernv_rng);
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*v = rng_whiten(rng, in_be64(rng->regs));
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put_cpu_var(rng);
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return 1;
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}
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EXPORT_SYMBOL_GPL(powernv_get_random_long);
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static __init void rng_init_per_cpu(struct powernv_rng *rng,
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struct device_node *dn)
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{
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int chip_id, cpu;
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chip_id = of_get_ibm_chip_id(dn);
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if (chip_id == -1)
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pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
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for_each_possible_cpu(cpu) {
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if (per_cpu(powernv_rng, cpu) == NULL ||
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cpu_to_chip_id(cpu) == chip_id) {
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per_cpu(powernv_rng, cpu) = rng;
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}
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}
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}
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static __init int rng_create(struct device_node *dn)
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{
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struct powernv_rng *rng;
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unsigned long val;
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rng = kzalloc(sizeof(*rng), GFP_KERNEL);
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if (!rng)
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return -ENOMEM;
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rng->regs = of_iomap(dn, 0);
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if (!rng->regs) {
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kfree(rng);
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return -ENXIO;
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}
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val = in_be64(rng->regs);
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rng->mask = val;
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rng_init_per_cpu(rng, dn);
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pr_info_once("Registering arch random hook.\n");
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ppc_md.get_random_long = powernv_get_random_long;
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return 0;
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}
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static __init int rng_init(void)
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{
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struct device_node *dn;
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int rc;
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for_each_compatible_node(dn, NULL, "ibm,power-rng") {
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rc = rng_create(dn);
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if (rc) {
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pr_err("Failed creating rng for %s (%d).\n",
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dn->full_name, rc);
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continue;
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}
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/* Create devices for hwrng driver */
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of_platform_device_create(dn, NULL, NULL);
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}
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return 0;
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}
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subsys_initcall(rng_init);

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