| Message ID | 1465376552-28129-1-git-send-email-yamada.masahiro@socionext.com |
|---|---|
| State | Accepted |
| Commit | 9c2f9b2da650907b928995350cc4e29480fb0f80 |
| Delegated to: | Masahiro Yamada |
| Headers | show |
2016-06-08 18:02 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > I noticed secondary CPUs sometimes fail to wake up, and the root > cause is that the sev instruction wakes up slave CPUs before the > preceding the register write is observed by them. > > The read-back of the accessed register does not guarantee the order. > In order to ensure the order between the register write and the sev > instruction, a dsb instruction should be executed prior to the sev. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Applied to u-boot-uniphier/master.
diff --git a/arch/arm/mach-uniphier/arm64/smp_kick_cpus.c b/arch/arm/mach-uniphier/arm64/smp_kick_cpus.c index 64412e0..5971ad2 100644 --- a/arch/arm/mach-uniphier/arm64/smp_kick_cpus.c +++ b/arch/arm/mach-uniphier/arm64/smp_kick_cpus.c @@ -21,11 +21,11 @@ void uniphier_smp_kick_all_cpus(void) rom_boot_rsv0 = map_sysmem(UNIPHIER_SMPCTRL_ROM_RSV0, SZ_8); writeq((u64)uniphier_secondary_startup, rom_boot_rsv0); - readq(rom_boot_rsv0); /* relax */ unmap_sysmem(rom_boot_rsv0); uniphier_smp_setup(); - asm("sev"); /* Bring up all secondary CPUs from Boot ROM into U-Boot */ + asm("dsb ishst\n" /* Ensure the write to ROM_RSV0 is visible */ + "sev"); /* Bring up all secondary CPUs from Boot ROM into U-Boot */ }
I noticed secondary CPUs sometimes fail to wake up, and the root cause is that the sev instruction wakes up slave CPUs before the preceding the register write is observed by them. The read-back of the accessed register does not guarantee the order. In order to ensure the order between the register write and the sev instruction, a dsb instruction should be executed prior to the sev. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Changes in v2: - Use "dsb ishst" instead of "dsb sy" arch/arm/mach-uniphier/arm64/smp_kick_cpus.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)