[ltt-dev] [PATCH 2/3] ltt: rework trace clock code for SH

[Giuseppe CAVALLARO]

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Hi Mathieu,

Mathieu Desnoyers wrote:
> This particular implementation seems ok, but I'd like stronger
> guarantees than that:
> 
> - That the clocksource selection will still work on future kernel
>   releases and other SH boards.

I guess this shouldn't be a problem. The code in the new Kernels has
been recently added for SuperH.

> - That sh_tmu_clocksource_read will never *ever* take any lock in any
>   future kernel version. Is that guaranteed by the clocksource API ?

Indeed, this should be ok for SH4 (i.e. using the TMU channels) but it
should be verified on other SuperH platforms. At first glance, I cannot
see any related issues for some devices but I could be wrong.

Another thing to be verified is the module_clk used for getting
the freq. It works fine on our platforms based on SH4.
Maybe, this could be ok on other SuperH platforms as well.
I don't know if somebody is actually using LTTng on SH targets.
I can only do my tests on STLinux platforms (based on SH4 CPUs).
In particular, I'm using a Kernel 2.6.32 plus LTTng release 198 and it
starts working on my side.

IMO, it's worth asking the SH mailing list for having a feedback about
the points above.

Moreover,  this implementation requires the clocksource_get_next
function. IIUC, it's not implemented in Linux so, maybe, the fisrt
patch, I sent you yesterday, could be also posted to the linux-kernel
for having other feedback and verify if it could actually help on other
side.

Regards
 Giuseppe

P.S. I'm reviewing the trace clock code for SH patch (see the version 2)
following the advice you gave me yesterday about the coding style.
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