lkml.org 
[lkml]   [2014]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] clocksource: arch_timer: Fix code to use physical timers when requested
Hi,

On Wed, Oct 08, 2014 at 12:38:57AM -0700, Sonny Rao wrote:
> This is a bug fix for using physical arch timers when
> the arch_timer_use_virtual boolean is false. It restores the
> arch_counter_get_cntpct() function after removal in
>
> 0d651e4e "clocksource: arch_timer: use virtual counters"
>
> We need this on certain ARMv7 systems which are architected like this:
>
> * The firmware doesn't know and doesn't care about hypervisor mode and
> we don't want to add the complexity of hypervisor there.
>
> * The firmware isn't involved in SMP bringup or resume.
>
> * The ARCH timer come up with an uninitialized offset between the
> virtual and physical counters. Each core gets a different random
> offset.
>
> * The device boots in "Secure SVC" mode.
>
> * Nothing has touched the reset value of CNTHCTL.PL1PCEN or
> CNTHCTL.PL1PCTEN (both default to 1 at reset)
>
> One example of such as system is RK3288 where it is much simpler to
> use the physical counter since there's nobody managing the offset and
> each time a core goes down and comes back up it will get reinitialized
> to some other random value.
>
> Fixes: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
> Acked-by: Olof Johansson <olof@lixom.net>

Has this been merged yet?

If not, you can add my Tested-by, it makes the Allwinner A31 boot
flawlessly with the arch timers (together with the patch "clocksource:
arch_timer: Allow the device tree to specify uninitialized timer
registers")

Thanks!
Maxime

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2014-11-20 10:21    [W:0.074 / U:0.492 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site