linux-kernel - RE: [PATCH v4] clocksource: timer-sp804: Fix read_current_timer() issue when clock source is not registered

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Message-Id: <20251216053801.331822-1-stephen.eta.zhou@gmail.com>
Date: Tue, 16 Dec 2025 13:38:01 +0800
From: stephen.eta.zhou@...il.com
To: linux@...ck-us.net
Cc: daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org,
	stephen.eta.zhou@...il.com,
	tglx@...utronix.de
Subject: RE: [PATCH v4] clocksource: timer-sp804: Fix read_current_timer() issue when clock source is not registered

Hi Guenter,

On Mon, 15 Dec 2025 15:18:37 -0800, Guenter Roeck wrote:
> This patch results in a crash when trying to boot integratorcp in qemu.

Thank you for pointing out the problem.

> sp804_read_delay_timer_read from read_current_timer+0x24/0x44
>
> This is not surprising since sp804_read_delay_timer_read() calls
> sp804_read() which dereferences sched_clkevt. sched_clkevt is not
> initialized for integratorcp.

Thank you for pointing out this issue.
I will work on fixing it and submit a new patch as soon as possible.

> static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
>                                                          const char *name,
>                                                          struct clk *clk,
>                                                          int use_sched_clock)
> {
> ...
> 	if (use_sched_clock) {
>                 sched_clkevt = clkevt;
>                 sched_clock_register(sp804_read, 32, rate);
>         }
> ...
> static int __init integrator_cp_of_init(struct device_node *np)
> {
> ...
> 		ret = sp804_clocksource_and_sched_clock_init(base,
>                                                              name, clk, 0);

Thanks.

Best regards,  
Stephen