Re: [PATCH/RFC 4/4] [WIP] ARM: shmobile: Enable ARM_GLOBAL_TIMER on Cortex-A9 MPCore SoCs
On Tue, Jul 31, 2018 at 6:08 PM Geert Uytterhoeven
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
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 (>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)
[] (unwind_backtrace) from [] (show_stack+0x10/0x14)
[] (show_stack) from [] (dump_stack+0x9c/0xd4)
[] (dump_stack) from [] (select_task_rq_fair+0x140/0xe8c)
[] (select_task_rq_fair) from []
(try_to_wake_up+0x210/0x3cc)
[] (try_to_wake_up) from [] (__wake_up_common+0xcc/0x140)
[] (__wake_up_common) from [] (__wake_up_locked+0x14/0x1c)
[] (__wake_up_locked) from [] (complete+0x38/0x48)
[] (complete) from [] (arch_cpu_idle_dead+0x2c/0x8c)
[] (arch_cpu_idle_dead) from [] (do_idle+0x98/0x148)
[] (do_idle) from [] (cpu_startup_entry+0x18/0x1c)
[] (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 -- ge...@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
[PATCH/RFC 4/4] [WIP] ARM: shmobile: Enable ARM_GLOBAL_TIMER on Cortex-A9 MPCore SoCs
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
---
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(-)
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,
--
2.17.1
