[tip: timers/core] RISC-V: time: initialize hrtimer based broadcast clock event device

[tip-bot2 for Conor Dooley]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     8b3b8fbb4896984b5564789a42240e4b3caddb61
Gitweb:        https://git.kernel.org/tip/8b3b8fbb4896984b5564789a42240e4b3caddb61
Author:        Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
AuthorDate:    Tue, 03 Jan 2023 19:41:00 +05:30
Committer:     Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
CommitterDate: Mon, 13 Feb 2023 13:10:16 +01:00

RISC-V: time: initialize hrtimer based broadcast clock event device

Similarly to commit 022eb8ae8b5e ("ARM: 8938/1: kernel: initialize
broadcast hrtimer based clock event device"), RISC-V needs to initiate
hrtimer based broadcast clock event device before C3STOP can be used.
Otherwise, the introduction of C3STOP for the RISC-V arch timer in
commit 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped
during CPU suspend") leaves us without any broadcast timer registered.
This prevents the kernel from entering oneshot mode, which breaks timer
behaviour, for example clock_nanosleep().

A test app that sleeps each cpu for 6, 5, 4, 3 ms respectively, HZ=250
& C3STOP enabled, the sleep times are rounded up to the next jiffy:
== CPU: 1 ==      == CPU: 2 ==      == CPU: 3 ==      == CPU: 4 ==
Mean: 7.974992    Mean: 7.976534    Mean: 7.962591    Mean: 3.952179
Std Dev: 0.154374 Std Dev: 0.156082 Std Dev: 0.171018 Std Dev: 0.076193
Hi: 9.472000      Hi: 10.495000     Hi: 8.864000      Hi: 4.736000
Lo: 6.087000      Lo: 6.380000      Lo: 4.872000      Lo: 3.403000
Samples: 521      Samples: 521      Samples: 521      Samples: 521

Link: https://lore.kernel.org/linux-riscv/YzYTNQRxLr7Q9JR0@spud/
Fixes: 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped during CPU suspend")
Suggested-by: Samuel Holland <samuel@xxxxxxxxxxxx>
Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
Reviewed-by: Samuel Holland <samuel@xxxxxxxxxxxx>
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230103141102.772228-2-apatel@xxxxxxxxxxxxxxxx
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 arch/riscv/kernel/time.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
index 8217b0f..1cf21db 100644
--- a/arch/riscv/kernel/time.c
+++ b/arch/riscv/kernel/time.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/of_clk.h>
+#include <linux/clockchips.h>
 #include <linux/clocksource.h>
 #include <linux/delay.h>
 #include <asm/sbi.h>
@@ -29,6 +30,8 @@ void __init time_init(void)
 
 	of_clk_init(NULL);
 	timer_probe();
+
+	tick_setup_hrtimer_broadcast();
 }
 
 void clocksource_arch_init(struct clocksource *cs)