How to implement a gp timer based sched_clock for C6A816X evm board in linux kernel

gary69393

Hello,

Since this board lack 32kHz sync time support, it has to use default jiffies-based sched_clock,

and tracer can't work with the use of default sched_clock due it's low resolution.

Questions as follows.

1. Does TI's engineer has the plan to implement sched_clock for those lack 32k clocksource?

2. I found there are eight gp timers for this board, if it is possible to register a new sched_clock

based on the gp timer? pls give some advice about it, thanks a lot!

BRs,

Gary

0 Afzal MOHAMMED over 13 years ago

Hi Gary,

Reg Q2,

Please define sched_clock() function in timer-gp.c (refer counter_32k.c) on the timer already registered for clocksource.

Regards

Afzal

0 gary69393 over 13 years ago in reply to Afzal MOHAMMED

Hi Afzal,

Thanks, I had added this func based on gp timer as follows. However after this modification,

kernel will hang when call omap_dm_timer_read_reg. Need more time to investigate it.

Regards,

Gary

0 HemantPedanekar over 13 years ago in reply to gary69393

Gary,

I would suggest to please refer changes mentioned @ http://www.mail-archive.com/linux-omap@vger.kernel.org/msg49148.html

Note that those may not apply directly since they were on recent kernel but can be used as reference.

Hemant

0 gary69393 over 13 years ago in reply to HemantPedanekar

I guess kernel can't boot is because sched_clock is called before omap2_gp_clocksource_init.

Hemant, thanks for you link, however I can't open the link due to the stupid firewall :(, I had to

try a proxy to open it.

Regards,

Gary

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