Patch "RISC-V: time: initialize hrtimer based broadcast clock event device" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     risc-v-time-initialize-hrtimer-based-broadcast-clock.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9e647799c930944cde33231596e76b2f9a2e314d
Author: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Date:   Tue Jan 3 19:41:00 2023 +0530

    RISC-V: time: initialize hrtimer based broadcast clock event device
    
    [ Upstream commit 8b3b8fbb4896984b5564789a42240e4b3caddb61 ]
    
    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>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
index 8aa70b519e04f..726860a490f36 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>
@@ -28,4 +29,6 @@ void __init time_init(void)
 
 	of_clk_init(NULL);
 	timer_probe();
+
+	tick_setup_hrtimer_broadcast();
 }