1 files changed, 96 insertions, 51 deletions

diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index 1a9d84371a4d..196aa70fe043 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -1,10 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * 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
@@ -16,36 +12,33 @@
 #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 powernv_rng {
+struct pnv_rng {
 	void __iomem *regs;
 	void __iomem *regs_real;
 	unsigned long mask;
 };
 
-static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
+static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng);
 
-
-int powernv_hwrng_present(void)
-{
-	struct powernv_rng *rng;
-
-	rng = get_cpu_var(powernv_rng);
-	put_cpu_var(rng);
-	return rng != NULL;
-}
-
-static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
+static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val)
 {
 	unsigned long parity;
 
 	/* Calculate the parity of the value */
-	asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
+	asm (".machine push;   \
+	      .machine power7; \
+	      popcntd %0,%1;   \
+	      .machine pop;"
+	     : "=r" (parity) : "r" (val));
 
 	/* xor our value with the previous mask */
 	val ^= rng->mask;
@@ -56,51 +49,74 @@ static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
 	return val;
 }
 
-int powernv_get_random_real_mode(unsigned long *v)
+static int pnv_get_random_darn(unsigned long *v)
 {
-	struct powernv_rng *rng;
+	unsigned long val;
 
-	rng = raw_cpu_read(powernv_rng);
+	/* Using DARN with L=1 - 64-bit conditioned random number */
+	asm volatile(PPC_DARN(%0, 1) : "=r"(val));
 
-	*v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
+	if (val == DARN_ERR)
+		return 0;
+
+	*v = val;
 
 	return 1;
 }
 
-int powernv_get_random_long(unsigned long *v)
+static int __init initialise_darn(void)
 {
-	struct powernv_rng *rng;
-
-	rng = get_cpu_var(powernv_rng);
+	unsigned long val;
+	int i;
 
-	*v = rng_whiten(rng, in_be64(rng->regs));
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return -ENODEV;
 
-	put_cpu_var(rng);
+	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(powernv_get_random_long);
+EXPORT_SYMBOL_GPL(pnv_get_random_long);
 
-static __init void rng_init_per_cpu(struct powernv_rng *rng,
+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 %s.\n", dn->full_name);
+		pr_warn("No ibm,chip-id found for %pOF.\n", dn);
 
 	for_each_possible_cpu(cpu) {
-		if (per_cpu(powernv_rng, cpu) == NULL ||
+		if (per_cpu(pnv_rng, cpu) == NULL ||
 		    cpu_to_chip_id(cpu) == chip_id) {
-			per_cpu(powernv_rng, cpu) = rng;
+			per_cpu(pnv_rng, cpu) = rng;
 		}
 	}
 }
 
 static __init int rng_create(struct device_node *dn)
 {
-	struct powernv_rng *rng;
+	struct pnv_rng *rng;
 	struct resource res;
 	unsigned long val;
 
@@ -126,30 +142,59 @@ static __init int rng_create(struct device_node *dn)
 
 	rng_init_per_cpu(rng, dn);
 
-	pr_info_once("Registering arch random hook.\n");
-
-	ppc_md.get_random_seed = powernv_get_random_long;
+	ppc_md.get_random_seed = pnv_get_random_long;
 
 	return 0;
 }
 
-static __init int rng_init(void)
+static int __init pnv_get_random_long_early(unsigned long *v)
 {
 	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);
+	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, rng_init);
+machine_subsys_initcall(powernv, pnv_rng_late_init);