>
>Xenomai is conceptually not known to I-pipe. This patch is about calling
>the well-defined kevent hook when the TSC frequency changes after a
>recalibration. ARM does something similar on frequency changes.
>
>> Linux may schedule a delayed work to refine tsc clock and update
>> tsc_khz which happen after Xenomai finsih init but tsc_scale and
>> tsc_shift still keep the value depending on origianl tsc clock
>> which is outdated. The difference between two clocks may cause
>> unexpected timing drift.
>>
>> For example:
>> [ 0.001731] tsc: Detected 2899.886 MHz TSC
>> [ 5.588387] tsc: Refined TSC clocksource calibration: 2903.999 MHz
>> cat /sys/module/xenomai/parameters/clockfreq
>> 2899886000
>> After patching, we like to use 2903.999 MHz.
>>
>> Signed-off-by: Hongzhan Chen <[email protected]>
>>
>> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
>> index 835856efd71f..e2ca733d76ee 100644
>> --- a/arch/x86/kernel/tsc.c
>> +++ b/arch/x86/kernel/tsc.c
>> @@ -1294,6 +1294,7 @@ static void tsc_refine_calibration_work(struct
>> work_struct *work)
>> u64 tsc_stop, ref_stop, delta;
>> unsigned long freq;
>> int cpu;
>> + unsigned int ipipe_freq;
>>
>> /* Don't bother refining TSC on unstable systems */
>> if (tsc_unstable)
>> @@ -1345,6 +1346,10 @@ static void tsc_refine_calibration_work(struct
>> work_struct *work)
>> /* Inform the TSC deadline clockevent devices about the recalibration */
>> lapic_update_tsc_freq();
>>
>> + /* notify xenomai about updated clockfreq */
>
>Drop the comment, it's misleading.
>
>> + ipipe_freq = tsc_khz * 1000;
>> + __ipipe_report_clockfreq_update(ipipe_freq);
>
>Why not simply
>
>__ipipe_report_clockfreq_update(tsc_khz * 1000);
There is following error if we apply this.
./include/linux/ipipe.h:177:53: error: lvalue required as unary ‘&’ operand
177 | __ipipe_notify_kevent(IPIPE_KEVT_CLOCKFREQ, &(freq))
| ^
arch/x86/kernel/tsc.c:1349:10: note: in expansion of macro
‘__ipipe_report_clockfreq_update’
1349 | __ipipe_report_clockfreq_update(tsc_khz * 1000);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
scripts/Makefile.build:262: recipe for target 'arch/x86/kernel/tsc.o' failed
Regards
Hongzhan Chen
>
>?
>
>> +
>> /* Update the sched_clock() rate to match the clocksource one */
>> for_each_possible_cpu(cpu)
>> set_cyc2ns_scale(tsc_khz, cpu, tsc_stop);
>
>The patch looks like valid candidate for 5.4, 4.19-cip and even 4.4-cip.
>
>Jan
>
>--
>Siemens AG, Technology
>Competence Center Embedded Linux
