RE: [PATCH] arm: mct: Don't reset the counter during boot and resume

[Kukjin Kim <kgene.kim@samsung.com>]

Doug Anderson wrote:
> 
> Chirantan,
> 
> On Tue, Jun 3, 2014 at 11:48 AM, Chirantan Ekbote
> <chirantan@chromium.org> wrote:
> > Unfortunately on some exynos systems, resetting the mct counter also
> > resets the architected timer counter.  This can cause problems if the
> > architected timer driver has already been initialized because the kernel
> > will think that the counter has wrapped around, causing a big jump in
> > printk timestamps and delaying any scheduled clock events until the
> > counter reaches the value it had before it was reset.
> >
> > The kernel code makes no assumptions about the initial value of the mct
> > counter so there is no reason from a software perspective to clear the
> > counter before starting it.  This also fixes the problems described in
> > the previous paragraph.
> >
> > Cc: Olof Johansson <olof@lixom.net>
> > Cc: Doug Anderson <dianders@chromium.org>
> > Cc: Kukjin Kim <kgene.kim@samsung.com>
> > Cc: Tomasz Figa <tomasz.figa@gmail.com>
> > Cc: linux-arm-kernel@lists.infradead.org
> > Cc: linux-samsung-soc@vger.kernel.org
> > Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
> > ---
> >  drivers/clocksource/exynos_mct.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> I can confirm that this fixes problems I described in
> <http://www.spinics.net/lists/linux-samsung-soc/msg29085.html>.  Now
> when I boot there's no mysterious delay and there's no big jump in
> time.
> 
> I'd love to see this in 3.16 so we can get rid of this annoying delay.
> 
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> Tested-by: Doug Anderson <dianders@chromium.org>

OK, I will queue this patch into fixes for 3.16.

Thanks,
Kukjin