Ad hoc testing with Lenovo Thinkpad 10 showed a stress
test could run for at least 24 hours with the patches,
compared to less than an hour without.
There is a patch in linux-next to delete C1E from BYT,
since it is problematic on multiple platforms.
I don't suppose that just disabling that state without disabling C6
is sufficient to fix the Thinkpad 10? (I'm betting not, but
it can't hurt to try -- you can use the "disable" attribute for the state
I think your choice of the PM_QOS sub-system here is the right one,
and that your selection of 20usec threshold is also a good choice
for what you want to do -- though on non-intel_idle machine somplace,
there may be some ACPI BIOS _CST with random number for C6 latency.
It would be interesting to see how your C6 residency (turbostat
--debug will show this to you)
and your battery life are changed by disabling C6 during MMC activity.