linux-kernel - Re: [RFC 4/5] clocksource: omap-timer: Introduce clocksource driver for OMAP SoCs

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Message-ID: <532243F5.4040609@ti.com>
Date:	Thu, 13 Mar 2014 18:49:09 -0500
From:	Joel Fernandes <joelf@...com>
To:	Tony Lindgren <tony@...mide.com>
CC:	Rob Herring <robh@...nel.org>, Tero Kristo <t-kristo@...com>,
	Nishanth Menon <nm@...com>, Suman Anna <s-anna@...com>,
	Felipe Balbi <balbi@...com>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC 4/5] clocksource: omap-timer: Introduce clocksource driver
 for OMAP SoCs

On 03/13/2014 03:48 PM, Tony Lindgren wrote:
> * Joel Fernandes <joelf@...com> [140313 13:43]:
>> We introduce functions to initialize clocksource and clockevent, use
>> CLOCKSOURCE_OF_DECLARE to declare the clocksource, and handle the clocksource
>> selection on a per-SoC basis (Currently only AM335x is supported). Powering up
>> of the timer will be done with the help of the mach-omap layer function that's
>> introduced earlier in the series.
>>
>> We make a local copy of dmtimer API for use by clocksource, the original
>> dmtimer API in plat-omap is kept as-is till the migration of all SoCs is
>> completed after which it can't be deleted.
>>
>> Signed-off-by: Joel Fernandes <joelf@...com>
>> ---
>>  drivers/clocksource/Makefile     |    1 +
>>  drivers/clocksource/omap-timer.c | 1157 ++++++++++++++++++++++++++++++++++++++
>>  drivers/clocksource/omap-timer.h |  422 ++++++++++++++
>>  3 files changed, 1580 insertions(+)
>>  create mode 100644 drivers/clocksource/omap-timer.c
>>  create mode 100644 drivers/clocksource/omap-timer.h
> 
> Hmm this leaves duplicate arch/arm/plat-omap/dmtimer.c code, please

Sure, ofcourse- but how else can we make sure everything works while we do
the migration in steps. We can get rid of the duplicate once everything is
migrated.

> sort out that issue too by allowing omap1 and omap3 still to use
> the legacy timer init functions but with timer code under
> drivers/clocksource/omap-timer.c.

Sorry, I didn't follow. I didn't see OMAP3 using legacy timer stuff. To me
it looks like OMAP3 migration should be straight forward along the same
lines as this RFC patchset. Could you elaborate a bit more what the legacy
functions you mentioned for OMAP1 are? I will just like to keep everything
in drivers/clocksource/ private for now till we're done migrating most
platforms. IMO once we get system timers working for omap2+, then we can
look into omap1 :)

> And not the that drivers/clocksource/omap-timer.h won't be needed at
> all, those defines can stay private to the drivers/clocksource/omap-timer.c.

Actually- I wanted it separate because omap-timer.c is already huge at 1157
lines. Infact the largest among the clocksource drivers. Is that fair?

> So this patch really should just be moving of the code to the new
> location.

To be honest, its not just a simple moving of code, there are new things
such as selecting correct timer, new functions for clockevent and
clocksource init, different handling of clocks etc.

Thanks,
-Joel
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