This adds the powernv_get_random_darn function which utilises the darn
instruction, introduced in POWER9. The powernv_get_random_darn function
is used as the ppc_md.get_random_seed on P9.
The DARN instruction can potentially throw an error, so we attempt to
register the powernv_get_random_darn function up to 10 times before
failing.
Signed-off-by: Matt Brown <matthew.brown....@gmail.com>
---
v3:
- add repeat attempts to register the ppc_md.get_random_seed
- fixed the PPC_DARN macro
- move DARN_ERR definition
- fixed commit message
v2:
- remove repeat darn attempts
- move hook to rng_init
---
arch/powerpc/include/asm/ppc-opcode.h | 4 ++++
arch/powerpc/platforms/powernv/rng.c | 35 ++++++++++++++++++++++++++++++++++-
2 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/ppc-opcode.h
b/arch/powerpc/include/asm/ppc-opcode.h
index c4ced1d..aabd150 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -134,6 +134,7 @@
#define PPC_INST_COPY 0x7c00060c
#define PPC_INST_COPY_FIRST 0x7c20060c
#define PPC_INST_CP_ABORT 0x7c00068c
+#define PPC_INST_DARN 0x7c0005e6
#define PPC_INST_DCBA 0x7c0005ec
#define PPC_INST_DCBA_MASK 0xfc0007fe
#define PPC_INST_DCBAL 0x7c2005ec
@@ -325,6 +326,9 @@
/* Deal with instructions that older assemblers aren't aware of */
#define PPC_CP_ABORT stringify_in_c(.long PPC_INST_CP_ABORT)
+#define PPC_DARN(t, l) stringify_in_c(.long PPC_INST_DARN | \
+ ___PPC_RT(t) | \
+ (((l) & 0x3) << 16))
#define PPC_DCBAL(a, b) stringify_in_c(.long PPC_INST_DCBAL | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_DCBZL(a, b) stringify_in_c(.long PPC_INST_DCBZL | \
diff --git a/arch/powerpc/platforms/powernv/rng.c
b/arch/powerpc/platforms/powernv/rng.c
index 5dcbdea..83b925c 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -16,11 +16,13 @@
#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>
+#define DARN_ERR 0xFFFFFFFFFFFFFFFFul
struct powernv_rng {
void __iomem *regs;
@@ -67,6 +69,21 @@ int powernv_get_random_real_mode(unsigned long *v)
return 1;
}
+int powernv_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;
+}
+
int powernv_get_random_long(unsigned long *v)
{
struct powernv_rng *rng;
@@ -135,8 +152,9 @@ static __init int rng_create(struct device_node *dn)
static __init int rng_init(void)
{
+ unsigned long darn_test;
struct device_node *dn;
- int rc;
+ int rc, i;
for_each_compatible_node(dn, NULL, "ibm,power-rng") {
rc = rng_create(dn);
@@ -150,6 +168,21 @@ static __init int rng_init(void)
of_platform_device_create(dn, NULL, NULL);
}
+ if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+ for (i = 0; i < 10; i++) {
+ if (powernv_get_random_darn(&darn_test)) {
+ ppc_md.get_random_seed =
+ powernv_get_random_darn;
+ break;
+ }
+
+ if (i == 9) {
+ pr_warn("Failed to use powernv_get_random_darn"\
+ "as get_random_seed");
+ }
+ }
+ }
+
return 0;
}
machine_subsys_initcall(powernv, rng_init);
--
2.9.3
