clocksource/drivers/timer-sun4i: Advertise a real minimum delta

sun4i_clkevt_next_event() compensates for the timer stop/start
synchronization delay by programming evt - TIMER_SYNC_TICKS into the
hardware interval register. The clockevent device currently advertises
TIMER_SYNC_TICKS as min_delta_ticks, so the clockevents core is allowed
to call set_next_event() with evt == TIMER_SYNC_TICKS.

That programs a zero-tick interval. With oneshot/highres/nohz timer
operation this can leave the next event stuck, which was observed as a
boot hang on Allwinner D1 after the clockevents core started reusing
forced minimum-delta events.

Advertise one extra tick instead, so the smallest event accepted by the
core still programs at least one hardware tick after the synchronization
compensation.

Fixes: 12e1480bcb ("clocksource: sun4i: Report the minimum tick that we can program")
Reported-by: Indrek Kruusa <[email protected]>
Closes: https://lore.kernel.org/linux-riscv/CA+fTLhgLmTY+exGujKf8OYYQvcEW5X5NJ_5sLq2AYL6zER2c0A@mail.gmail.com/
Assisted-by: Codex:gpt-5.5
Signed-off-by: Felix Yan <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Tested-by: Indrek Kruusa <[email protected]>
Acked-by: Jernej Skrabec <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/linux-riscv/CA+fTLhgLmTY+exGujKf8OYYQvcEW5X5NJ_5sLq2AYL6zER2c0A@mail.gmail.com/
Link: https://patch.msgid.link/[email protected]

drivers/clocksource/timer-sun4i.c

@@ -208,7 +208,7 @@ static int __init sun4i_timer_init(struct device_node *node)
 	sun4i_timer_clear_interrupt(timer_of_base(&to));
 
 	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
-					TIMER_SYNC_TICKS, 0xffffffff);
+					TIMER_SYNC_TICKS + 1, 0xffffffff);
 
 	/* Enable timer0 interrupt */
 	val = readl(timer_of_base(&to) + TIMER_IRQ_EN_REG);