On 20/07/17 13:22, Peter Zijlstra wrote:
On Thu, Jul 13, 2017 at 07:02:37PM -0700, Saravana Kannan wrote:
In all Qualcomm chipsets (well, at least the ones that have been used in Android devices so far), we can switch the frequency of any CPU from any other CPU. If we can do that even without fast switching, why wouldn't any theoretical fast switching be incapable of supporting this? Is this a limitation specific to x86 that we are assuming all architectures and platforms are going to have?
So the typical implementation of fast switching we're thinking of is the CPU writing the DVFS request into a machine register. Now machine registers are typically per logical CPU.
But, if ARM decides to architect and move to it to a system/machine register, we will end up with the same limitation :( IMO.
For now with SCMI kind of interface, there's no such limitation as yoalready mentioned in the follow up email. -- Regards, Sudeep