| Message ID | 20180731160855.6758-5-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Simon Horman |
| Headers | show |
| Series | ARM: shmobile: Enable ARM_GLOBAL_TIMER on Cortex-A9 MPCore | expand |
On Tue, Jul 31, 2018 at 6:08 PM Geert Uytterhoeven <geert+renesas@glider.be> wrote: > SH-Mobile AG5 and R-Car H1 SoCs are based on the Cortex-A9 MPCore, which > includes a global timer. > > Enable the ARM global timer on these SoCs, which will be used for: > - the scheduler clock, improving scheduler accuracy from 10 ms to 3 or > 4 ns, > - delay loops, allowing removal of calls to shmobile_init_delay() from > the corresponding machine vectors. > > Note that when using an old DTB lacking the global timer, the kernel > will still work. However, loops-per-jiffies will no longer be preset, > and the delay loop will need to be calibrated during boot. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> This seems to cause random system resume issues on the venerable SH-Mobile AG5, ranging from plain lockups to RCU warnings: WARNING: suspicious RCU usage 4.18.0-kzm9g-00218-gaf4425056bd09e9e #38 Not tainted ----------------------------- kernel/sched/fair.c:6231 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 2, debug_locks = 1 3 locks held by swapper/1/0: #0: 6d7f5781 ((cpu_died).wait.lock){....}, at: complete+0x14/0x48 #1: 84ce6f8e (&p->pi_lock){-.-.}, at: try_to_wake_up+0x30/0x3cc #2: 93591133 (rcu_read_lock){....}, at: select_task_rq_fair+0x5c/0xe8c stack backtrace: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.18.0-kzm9g-00218-gaf4425056bd09e9e #38 Hardware name: Generic SH73A0 (Flattened Device Tree) [<c010f22c>] (unwind_backtrace) from [<c010bab0>] (show_stack+0x10/0x14) [<c010bab0>] (show_stack) from [<c0599750>] (dump_stack+0x9c/0xd4) [<c0599750>] (dump_stack) from [<c01542c8>] (select_task_rq_fair+0x140/0xe8c) [<c01542c8>] (select_task_rq_fair) from [<c0149494>] (try_to_wake_up+0x210/0x3cc) [<c0149494>] (try_to_wake_up) from [<c016355c>] (__wake_up_common+0xcc/0x140) [<c016355c>] (__wake_up_common) from [<c01636a8>] (__wake_up_locked+0x14/0x1c) [<c01636a8>] (__wake_up_locked) from [<c016450c>] (complete+0x38/0x48) [<c016450c>] (complete) from [<c010d66c>] (arch_cpu_idle_dead+0x2c/0x8c) [<c010d66c>] (arch_cpu_idle_dead) from [<c014edec>] (do_idle+0x98/0x148) [<c014edec>] (do_idle) from [<c014f1fc>] (cpu_startup_entry+0x18/0x1c) [<c014f1fc>] (cpu_startup_entry) from [<4010246c>] (0x4010246c) Given secondary CPU startup is already quite flaky on this SoC, perhaps it's best to leave it alone? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
On Tue, Aug 21, 2018 at 9:37 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Tue, Jul 31, 2018 at 6:08 PM Geert Uytterhoeven > <geert+renesas@glider.be> wrote: > > SH-Mobile AG5 and R-Car H1 SoCs are based on the Cortex-A9 MPCore, which > > includes a global timer. > > > > Enable the ARM global timer on these SoCs, which will be used for: > > - the scheduler clock, improving scheduler accuracy from 10 ms to 3 or > > 4 ns, > > - delay loops, allowing removal of calls to shmobile_init_delay() from > > the corresponding machine vectors. > > > > Note that when using an old DTB lacking the global timer, the kernel > > will still work. However, loops-per-jiffies will no longer be preset, > > and the delay loop will need to be calibrated during boot. > > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > > This seems to cause random system resume issues on the venerable SH-Mobile > AG5, ranging from plain lockups to RCU warnings: > > WARNING: suspicious RCU usage > 4.18.0-kzm9g-00218-gaf4425056bd09e9e #38 Not tainted > ----------------------------- > kernel/sched/fair.c:6231 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > > RCU used illegally from offline CPU! > rcu_scheduler_active = 2, debug_locks = 1 > 3 locks held by swapper/1/0: > #0: 6d7f5781 ((cpu_died).wait.lock){....}, at: complete+0x14/0x48 > #1: 84ce6f8e (&p->pi_lock){-.-.}, at: try_to_wake_up+0x30/0x3cc > #2: 93591133 (rcu_read_lock){....}, at: select_task_rq_fair+0x5c/0xe8c > > stack backtrace: > CPU: 1 PID: 0 Comm: swapper/1 Not tainted > 4.18.0-kzm9g-00218-gaf4425056bd09e9e #38 > Hardware name: Generic SH73A0 (Flattened Device Tree) > [<c010f22c>] (unwind_backtrace) from [<c010bab0>] (show_stack+0x10/0x14) > [<c010bab0>] (show_stack) from [<c0599750>] (dump_stack+0x9c/0xd4) > [<c0599750>] (dump_stack) from [<c01542c8>] (select_task_rq_fair+0x140/0xe8c) > [<c01542c8>] (select_task_rq_fair) from [<c0149494>] > (try_to_wake_up+0x210/0x3cc) > [<c0149494>] (try_to_wake_up) from [<c016355c>] (__wake_up_common+0xcc/0x140) > [<c016355c>] (__wake_up_common) from [<c01636a8>] (__wake_up_locked+0x14/0x1c) > [<c01636a8>] (__wake_up_locked) from [<c016450c>] (complete+0x38/0x48) > [<c016450c>] (complete) from [<c010d66c>] (arch_cpu_idle_dead+0x2c/0x8c) > [<c010d66c>] (arch_cpu_idle_dead) from [<c014edec>] (do_idle+0x98/0x148) > [<c014edec>] (do_idle) from [<c014f1fc>] (cpu_startup_entry+0x18/0x1c) > [<c014f1fc>] (cpu_startup_entry) from [<4010246c>] (0x4010246c) > > Given secondary CPU startup is already quite flaky on this SoC, perhaps > it's best to leave it alone? Last time I saw that was on v4.19-rc7 in October. Presumably that was fixed in the big RCU update in v4.20-rc1, so I think it's safe to use the Global Timer on SH Mobile AG5 now. Thoughts? Thanks! Gr{oetje,eeting}s, Geert
diff --git a/arch/arm/mach-shmobile/Kconfig b/arch/arm/mach-shmobile/Kconfig index 94e9431d92b87405..d39ab39bba92b124 100644 --- a/arch/arm/mach-shmobile/Kconfig +++ b/arch/arm/mach-shmobile/Kconfig @@ -92,6 +92,7 @@ config ARCH_R8A7778 config ARCH_R8A7779 bool "R-Car H1 (R8A77790)" + select ARM_GLOBAL_TIMER select ARCH_RCAR_GEN1 config ARCH_R8A7790 @@ -133,5 +134,6 @@ config ARCH_RZN1 config ARCH_SH73A0 bool "SH-Mobile AG5 (R8A73A00)" select ARCH_RMOBILE + select ARM_GLOBAL_TIMER select RENESAS_INTC_IRQPIN endif diff --git a/arch/arm/mach-shmobile/setup-r8a7779.c b/arch/arm/mach-shmobile/setup-r8a7779.c index b13ec9088ce5354c..86406e3f9b22e31f 100644 --- a/arch/arm/mach-shmobile/setup-r8a7779.c +++ b/arch/arm/mach-shmobile/setup-r8a7779.c @@ -72,7 +72,6 @@ static const char *const r8a7779_compat_dt[] __initconst = { DT_MACHINE_START(R8A7779_DT, "Generic R8A7779 (Flattened Device Tree)") .smp = smp_ops(r8a7779_smp_ops), .map_io = r8a7779_map_io, - .init_early = shmobile_init_delay, .init_irq = r8a7779_init_irq_dt, .init_late = shmobile_init_late, .dt_compat = r8a7779_compat_dt, diff --git a/arch/arm/mach-shmobile/setup-sh73a0.c b/arch/arm/mach-shmobile/setup-sh73a0.c index cc08aa752244764a..eb4a62fa42895ebe 100644 --- a/arch/arm/mach-shmobile/setup-sh73a0.c +++ b/arch/arm/mach-shmobile/setup-sh73a0.c @@ -56,7 +56,6 @@ static const char *const sh73a0_boards_compat_dt[] __initconst = { DT_MACHINE_START(SH73A0_DT, "Generic SH73A0 (Flattened Device Tree)") .smp = smp_ops(sh73a0_smp_ops), .map_io = sh73a0_map_io, - .init_early = shmobile_init_delay, .init_machine = sh73a0_generic_init, .init_late = shmobile_init_late, .dt_compat = sh73a0_boards_compat_dt,
SH-Mobile AG5 and R-Car H1 SoCs are based on the Cortex-A9 MPCore, which includes a global timer. Enable the ARM global timer on these SoCs, which will be used for: - the scheduler clock, improving scheduler accuracy from 10 ms to 3 or 4 ns, - delay loops, allowing removal of calls to shmobile_init_delay() from the corresponding machine vectors. Note that when using an old DTB lacking the global timer, the kernel will still work. However, loops-per-jiffies will no longer be preset, and the delay loop will need to be calibrated during boot. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- arch/arm/mach-shmobile/Kconfig | 2 ++ arch/arm/mach-shmobile/setup-r8a7779.c | 1 - arch/arm/mach-shmobile/setup-sh73a0.c | 1 - 3 files changed, 2 insertions(+), 2 deletions(-)