From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.ripard@free-electrons.com (Maxime Ripard) Date: Thu, 20 Nov 2014 09:49:00 +0100 Subject: [PATCH v4] clocksource: arch_timer: Fix code to use physical timers when requested In-Reply-To: <1412753937-29343-1-git-send-email-sonnyrao@chromium.org> References: <1412753937-29343-1-git-send-email-sonnyrao@chromium.org> Message-ID: <20141120084900.GC24143@lukather> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 at vger.kernel.org > Signed-off-by: Sonny Rao > Acked-by: Olof Johansson 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 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: