[PATCH] Revert "clocksource/drivers/riscv: Events are stopped during CPU suspend"

[Conor Dooley]

From: Conor Dooley <conor.dooley at microchip.com>

This reverts commit 232ccac1bd9b5bfe73895f527c08623e7fa0752d.
If an AXI read to the PCIe controller on PolarFire SoC times out, the
system will stall, with an expected:
	 io scheduler mq-deadline registered
	 io scheduler kyber registered
	 microchip-pcie 2000000000.pcie: host bridge /soc/pcie at 2000000000 ranges:
	 microchip-pcie 2000000000.pcie:      MEM 0x2008000000..0x2087ffffff -> 0x0008000000
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: axi read request error
	 microchip-pcie 2000000000.pcie: axi read timeout
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 Freeing initrd memory: 7336K
	 mc_event_handler: 667402 callbacks suppressed
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	 microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	 mc_event_handler: 666588 callbacks suppressed
<truncated>
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	mc_event_handler: 666748 callbacks suppressed
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	rcu: 	0-...0: (1 GPs behind) idle=19f/1/0x4000000000000002 softirq=34/36 fqs=2626
		(detected by 1, t=5256 jiffies, g=-1151, q=1143 ncpus=4)
	Task dump for CPU 0:
	task:swapper/0       state:R  running task     stack:    0 pid:    1 ppid:     0 flags:0x00000008
	Call Trace:
	mc_event_handler: 666648 callbacks suppressed

 With this patch applied, the system just locks up without RCU stalling:
	io scheduler mq-deadline registered
	io scheduler kyber registered
	microchip-pcie 2000000000.pcie: host bridge /soc/pcie at 2000000000 ranges:
	microchip-pcie 2000000000.pcie:      MEM 0x2008000000..0x2087ffffff -> 0x0008000000
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: axi read request error
	microchip-pcie 2000000000.pcie: axi read timeout
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: sec error in pcie2axi buffer
	microchip-pcie 2000000000.pcie: ded error in pcie2axi buffer
	Freeing initrd memory: 7332K

Link: https://lore.kernel.org/linux-riscv/YzYTNQRxLr7Q9JR0@spud/
Fixes: 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped during CPU suspend")
Signed-off-by: Conor Dooley <conor.dooley at microchip.com>
---
I don't really want to post a revert, but it's been nearly a month since
I posted about my issue initially & 2 weeks without a reply to Palmer's
comments.
CC: samuel at sholland.org
CC: aou at eecs.berkeley.edu
CC: atishp at atishpatra.org
CC: daniel.lezcano at linaro.org
CC: dmitriy at oss-tech.org
CC: linux-kernel at vger.kernel.org
CC: linux-riscv at lists.infradead.org
CC: palmer at dabbelt.com
CC: paul.walmsley at sifive.com
CC: tglx at linutronix.de
---
 drivers/clocksource/timer-riscv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 969a552da8d2..a0d66fabf073 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -51,7 +51,7 @@ static int riscv_clock_next_event(unsigned long delta,
 static unsigned int riscv_clock_event_irq;
 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
 	.name			= "riscv_timer_clockevent",
-	.features		= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
+	.features		= CLOCK_EVT_FEAT_ONESHOT,
 	.rating			= 100,
 	.set_next_event		= riscv_clock_next_event,
 };
-- 
2.38.0