Hi Bjorn, On Mon, Dec 7, 2020 at 2:33 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > > For a bunch of rails we really don't do anything with them in Linux. > These are things like modem voltage rails that the modem manages these > itself and core rails (like IO rails) that are setup to just > automagically do the right thing by the firmware. > > Let's stop even listing those rails in our device tree. > > The net result of this is that some of these rails might be able to go > down to a lower voltage or perhaps transition to LPM (low power mode) > sometimes. > > Here's a list of what we're doing and why: > > * L1A - only goes to SoC and doesn't seem associated with any > particular peripheral. Kernel isn't doing anything with > this. Removing from dts. NET IMPACT: rail might drop from 1.2V to > 1.178V and switch to LPM in some cases depending on firmware. > * L2A - only goes to SoC and doesn't seem associated with any > particular peripheral. Kernel isn't doing anything with > this. Removing from dts. NET IMPACT: rail might switch to LPM in > some cases depending on firmware. > * L3A - only goes to SoC and doesn't seem associated with any > particular peripheral. Kernel isn't doing anything with > this. Removing from dts. NET IMPACT: rail might switch to LPM in > some cases depending on firmware. > * L5A - seems to be totally unused as far as I can tell and doesn't > even come off QSIP. Removing from dts. > * L6A - only goes to SoC and doesn't seem associated with any > particular peripheral (I think?). Kernel isn't doing anything with > this. Removing from dts. NET IMPACT: rail might switch to LPM in > some cases depending on firmware. > * L16A - Looks like this is only used for internal RF stuff. Removing > from dts. NET IMPACT: rail might switch to LPM in some cases > depending on firmware. > * L1C - Just goes to WiFi / Bluetooth. Trust how IDP has this set and > put this back at 1.616V min. > * L4C - This goes out to the eSIM among other places. This looks like > it's intended to be for SIM card and modem manages. NET IMPACT: > rail might switch to LPM in some cases depending on firmware. > * L5C - This goes to the physical SIM. This looks like it's intended > to be for SIM card and modem manages. NET IMPACT: rail might drop > from 1.8V to 1.648V and switch to LPM in some cases depending on > firmware. > > NOTE: in general for anything which is supposed to be managed by Linux > I still left it all forced to HPM since I'm not 100% sure that all the > needed calls to regulator_set_load() are in place and HPM is safer. > Switching more things to LPM can happen in a future patch. > > ALSO NOTE: Power measurements showed no measurable difference after > applying this patch, so perhaps it should be viewed more as a cleanup > than any power savings. > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > --- > > arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 82 ++------------------ > 1 file changed, 7 insertions(+), 75 deletions(-) We've been running with this in the downstream tree since December 8th and nobody has yelled. You can see <https://crrev.com/c/2573506>. Is it a good time for it to land upstream? Thanks! -Doug
