On Tue, Apr 8, 2014 at 4:04 AM, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote: > ARM arch timers are tightly coupled with the CPU logic and lose context > on platform implementing HW power management when cores are powered > down at run-time. Marking the arch timers as C3STOP regardless of power > management capabilities causes issues on platforms with no power management, > since in that case the arch timers cannot possibly enter states where the > timer loses context at runtime and therefore can always be used as a high > resolution clockevent device. > > In order to fix the C3STOP issue in a way compliant with how real HW > works, this patch adds a boolean property to the arch timer bindings > to define if the arch timer is managed by an always-on power domain. > > This power domain is present on all ARM platforms to date, and manages > HW that must not be turned off, whatever the state of other HW > components (eg power controller). On platforms with no power management > capabilities, it is the only power domain present, which encompasses > and manages power supply for all HW components in the system. > > If the timer is powered by the always-on power domain, the always-on > property must be present in the bindings which means that the timer cannot > be shutdown at runtime, so it is not a C3STOP clockevent device. > If the timer binding does not contain the always-on property, the timer is > assumed to be power-gateable, hence it must be defined as a C3STOP > clockevent device. > > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> > Cc: Magnus Damm <damm@xxxxxxxxxxxxx> > Cc: Marc Carino <marc.ceeeee@xxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> Acked-by: Rob Herring <robh@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
