Commit c25769fd authored by Paul Mackerras's avatar Paul Mackerras Committed by Michael Ellerman
Browse files

powerpc/microwatt: Add support for hardware random number generator 



Microwatt's hardware RNG is accessed using the DARN instruction.

Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarSegher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/YMwXPHlV/ZleiQUY@thinks.paulus.ozlabs.org
parent 48b545b8

arch/powerpc/platforms/microwatt/Kconfig

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@@ -7,6 +7,7 @@ config PPC_MICROWATT 
	select PPC_ICP_NATIVE

	select PPC_NATIVE

	select PPC_UDBG_16550

	select ARCH_RANDOM

	help

          This option enables support for FPGA-based Microwatt implementations.

arch/powerpc/platforms/microwatt/Makefile

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obj-y	+= setup.o
 
obj-y	+= setup.o rng.o

arch/powerpc/platforms/microwatt/rng.c

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// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * Derived from arch/powerpc/platforms/powernv/rng.c, which is:

 * Copyright 2013, Michael Ellerman, IBM Corporation.

 */



#define pr_fmt(fmt)	"microwatt-rng: " fmt



#include <linux/kernel.h>

#include <linux/smp.h>

#include <asm/archrandom.h>

#include <asm/cputable.h>

#include <asm/machdep.h>



#define DARN_ERR 0xFFFFFFFFFFFFFFFFul



int microwatt_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 __init int rng_init(void)

{

	unsigned long val;

	int i;



	for (i = 0; i < 10; i++) {

		if (microwatt_get_random_darn(&val)) {

			ppc_md.get_random_seed = microwatt_get_random_darn;

			return 0;

		}

	}



	pr_warn("Unable to use DARN for get_random_seed()\n");



	return -EIO;

}

machine_subsys_initcall(, rng_init);