On Thu, Sep 10, 2015 at 06:29:53PM -0400, Jon Masters wrote: > On 08/24/2015 01:01 PM, fu.wei@xxxxxxxxxx wrote: > > > + /* > > + * Get the frequency of system counter from the cp15 interface of ARM > > + * Generic timer. We don't need to check it, because if it returns "0", > > + * system would panic in very early stage. > > + */ > > + gwdt->clk = arch_timer_get_cntfrq(); > > Just thinking out loud... > > What happens later if we virtualize this device within KVM/QEMU/Xen and > then live migrate to another system in which the frequency changes? > I don't know, but I would suspect that we might end up in all kinds of trouble if clocks can change like that, and not just in this driver. Many drivers make the assumption that clock rates are not changed under the hood. If it can happen, shouldn't there be a callback into the drivers using the affected clock(s) ? Also, it seems to me that changing a clock like that would be inherently unsafe. For example, what will happen if the system is stopped and migrated right after the clock frequency is read, but before the returned value is used ? Can that happen ? Or does it only happen during suspend/resume cycles, if it happens ? Thanks, Guenter -- 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
