[PATCH 1/3] clocksource/drivers/timer-mediatek: Fix random crash at boot

[Luca Leonardo Scorcia <l.scorcia@gmail.com>]

MediaTek bootloaders generally enable APXGPT timers at boot. This means
that a timer IRQ can sometimes happen between the IRQ line request and the
configuration of the clock event handler. This leads to a hard crash with
an instruction abort, branch to pc 0x0 in mtk_gpt_interrupt handler as
clkevt is null.

To avoid this issue request the IRQ with IRQF_NO_AUTOEN and enable it
explicitly after the clock event is configured.

Issue was reported and fix tested on the Lenovo Tab E7 (TB-7104F, mt8167).

Fixes: a0858f937960 ("clocksource/drivers/timer-mediatek: Convert the driver to timer-of")
Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
---
Credits for issue discovery and suggested fix go to          
matemiller992 on postmarketOS forums. I am submitting it upstream with     
permission. Not adding Reported-by or Suggested-by tags because it was     
requested not to share real name.    

 drivers/clocksource/timer-mediatek.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-mediatek.c b/drivers/clocksource/timer-mediatek.c
index 7bcb4a3f26fb..e20075b09fab 100644
--- a/drivers/clocksource/timer-mediatek.c
+++ b/drivers/clocksource/timer-mediatek.c
@@ -277,7 +277,7 @@ static struct timer_of to = {
 	},
 
 	.of_irq = {
-		.flags = IRQF_TIMER | IRQF_IRQPOLL,
+		.flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_NO_AUTOEN,
 	},
 };
 
@@ -298,6 +298,7 @@ static int __init mtk_syst_init(struct device_node *node)
 
 	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
 					TIMER_SYNC_TICKS, 0xffffffff);
+	enable_irq(timer_of_irq(&to));
 
 	return 0;
 }
@@ -334,6 +335,7 @@ static int __init mtk_gpt_init(struct device_node *node)
 					TIMER_SYNC_TICKS, 0xffffffff);
 
 	mtk_gpt_enable_irq(&to, TIMER_CLK_EVT);
+	enable_irq(timer_of_irq(&to));
 
 	return 0;
 }
-- 
2.43.0