Re: [PATCH 0/4] ARM: da850: enable cpufreq in DT mode

czw., 21 mar 2019 o 16:29 David Lechner [off-list ref] napisał(a):

On 3/21/19 9:10 AM, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

This series adds cpufreq-dt operating points for da850 boards supported
with device tree (da850-lcdk, da850-lego-ev3, da850-evm) and also
includes a fix for the da850-evm boardfile which checks an unset variable
to determine the highest available frequency for cpufreq.

I can't find any old threads about this, but I recall that there was a
problem with the USB OHCI controller breaking when switching frequencies.
It didn't happen all of the time, but often enough that it made using
cpufreq unusable for me. Is this still a problem?

Yes, it's still a problem, but it's bug-compatible with the legacy BSP
from TI (project arago). I've spent some time trying to figure out the
culprit at the time you were working on the clock driver, but
eventually gave up. I think it's some kind of a HW issue. The
controller would simple die after a couple transitions.

Bart

Also, a big-picture question. On boards with fixed regulators, what is
the benefit of enabling frequency scaling? The power savings aspect
seems negligible (< 1% in my tests) since the voltage cannot be changed.