Re: [patch 20/48] x86/apic: Enable TSC coupled programming mode

[Thomas Gleixner]

On Mon, Mar 02 2026 at 18:29, Nathan Chancellor wrote:
>
> After this change landed in -next as commit f246ec3478cf ("x86/apic:
> Enable TSC coupled programming mode"), two of my Intel-based test
> machines fail to boot. Unfortunately, I do not think I have any serial
> access on these, so I have little introspective ability. Is there any
> information I can provide or patches I can test to try and help figure
> out what is going on here? I have attached the output of lscpu of both
> machines, in case there is some common thread there.

Grmbl. I stared at it for a while and I have a suspicion. Can you try
the patch below and also provide from one of the machines the output of

  dmesg | grep -i tsc

In case that does not work, I'll send a debug patch in reply to this
mail.

Thanks,

        tglx
---
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -404,6 +404,7 @@ static void tk_setup_internals(struct ti
 		 */
 		clocks_calc_mult_shift(&tk->cs_ns_to_cyc_mult, &tk->cs_ns_to_cyc_shift,
 				       NSEC_PER_MSEC, clock->freq_khz, 3600 * 1000);
+		tk->cs_ns_to_cyc_maxns = div_u64(clock->mask, tk->cs_ns_to_cyc_mult);
 	}
 }