On 20/12/12 12:22, Peter De Schrijver wrote: >>>>> + >>>>> + /* CNTFRQ */ >>>>> + asm("mcr p15, 0, %0, c14, c0, 0\n" : : "r" (freq)); >>>>> + asm("mrc p15, 0, %0, c14, c0, 0\n" : "=r" (val)); >>>>> + BUG_ON(val != freq); >>>> >>>> This is scary. CNTFRQ is only writable from secure mode, and will >>>> explode in any other situation. >>>> >>>> Also, writing to CNTFRQ doesn't change the timer frequency! This is just >>>> a way for secure mode to tell the rest of the world the frequency the >>>> timer is ticking at. Unless you've wired the input clock to be able to >>>> change the frequency? >>> >>> ATM, our upstream kernel is expected in secure mode. This situation >>> may be changed later, though.... >> >> I appreciate this. But I expect this kernel to be also used on the >> non-secure side if someone tried to run KVM with it. And this would go >> bang right away. >> > > But the guest wouldn't necessarily have this peripheral, or any other Tegra114 > peripheral for that matter? The problem is not so much the guest but the host. The host has to be booted in non-secure, so just saying "we do not support non-secure" is not a very convincing argument. Unless of course you've already decided that you don't want to support KVM on this SoC... M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html