On 08/03/2017 06:12 PM, Matt Brown wrote:
> 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 you return directly here you can avoid the (i == 9) conditional every
iteration of the
loop by moving the pr_warn to just outside the loop.
-Tyrel
> + }
> +
> + if (i == 9) {
> + pr_warn("Failed to use powernv_get_random_darn"\
> + "as get_random_seed");
> + }
> + }
> + }
> +
> return 0;
> }
> machine_subsys_initcall(powernv, rng_init);
>
