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clocksource/drivers/timer-sp804: Fix an Oops when read_current_timer is called on ARM32 platforms where the SP804 is not registered as the sched_clock.

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On SP804, the delay timer shares the same clkevt instance with
sched_clock. On some platforms, when
sp804_clocksource_and_sched_clock_init is called with use_sched_clock
not set to 1, sched_clkevt is not properly initialized. However,
sp804_register_delay_timer is invoked unconditionally, and
read_current_timer() subsequently calls sp804_read on an uninitialized
sched_clkevt, leading to a kernel Oops when accessing
sched_clkevt->value.

Declare a dedicated clkevt instance exclusively for delay timer,
instead of sharing the same clkevt with sched_clock.  This ensures
that read_current_timer continues to work correctly regardless of
whether SP804 is selected as the sched_clock.

Fixes: 640594a04f ("clocksource/drivers/timer-sp804: Fix read_current_timer() issue when clock source is not registered")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512250520.APOMkYRQ-lkp@intel.com/
Signed-off-by: Stephen Eta Zhou <stephen.eta.zhou@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://patch.msgid.link/20251225-fix_timersp804-v2-1-a366d7157f58@gmail.com
This commit is contained in:
Stephen Eta Zhou 2025-12-25 16:16:31 +08:00 committed by Daniel Lezcano
parent f555fd9ebe
commit 694921a93f
1 changed files with 9 additions and 5 deletions
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14
drivers/clocksource/timer-sp804.c
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@ -106,21 +106,25 @@ static u64 notrace sp804_read(void)
return ~readl_relaxed(sched_clkevt->value);
}
/* Register delay timer backed by the hardware counter */
#ifdef CONFIG_ARM
static struct delay_timer delay;
static struct sp804_clkevt *delay_clkevt;
static unsigned long sp804_read_delay_timer_read(void)
{
return sp804_read();
return ~readl_relaxed(delay_clkevt->value);
}
static void sp804_register_delay_timer(int freq)
static void sp804_register_delay_timer(struct sp804_clkevt *clk, int freq)
{
delay_clkevt = clk;
delay.freq = freq;
delay.read_current_timer = sp804_read_delay_timer_read;
register_current_timer_delay(&delay);
}
#else
static inline void sp804_register_delay_timer(int freq) {}
static inline void sp804_register_delay_timer(struct sp804_clkevt *clk, int freq) {}
#endif
static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
@ -135,8 +139,6 @@ static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
if (rate < 0)
return -EINVAL;
sp804_register_delay_timer(rate);
clkevt = sp804_clkevt_get(base);
writel(0, clkevt->ctrl);
@ -152,6 +154,8 @@ static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
clocksource_mmio_init(clkevt->value, name,
rate, 200, 32, clocksource_mmio_readl_down);
sp804_register_delay_timer(clkevt, rate);
if (use_sched_clock) {
sched_clkevt = clkevt;
sched_clock_register(sp804_read, 32, rate);