Hi, On 3/14/22 15:59, Mark Pearson wrote: > > Hi Hans & Mario > > Thanks for all the comments. > > On 2022-03-14 10:43, Hans de Goede wrote: >> Hi Mario, >> >> On 3/14/22 14:39, Limonciello, Mario wrote: >>> [Public] >>> >>>>> >>>>> I cycled through a few different implementations but came down on what I >>>>> proposed. I considered 6 values - but I don't think that makes sense and >>>>> makes it overall more complicated than it needs to be and less flexible. >>>> >>>> Ah, so to be clear, my 2 scenarios above were theoretical scenarios, >>>> because I'm wondering how the firmware API here actually looks like, >>>> something which so far is not really clear to me. >>>> >>>> When you say that you considered using 6 values, then I guess that >>>> the firmware API actually offers 6 values which we can write to a single slot: >>>> ac-low-power,dc-lowpower,ac-balanced,dc-balanced,ac-performance,dc- >>>> performance >>>> >>>> ? >>>> >>>> But that is not what the RFC patch that started this thread shows at all, >>>> the API to the driver is totally unchanged and does not get passed >>>> any info on ac/dc selection ? So it seems to me that the ACPI API Linux >>>> uses for this writes only 1 of 3 values to a single slot and the EC automatically >>>> switches between say ac-balanced and dc-balanced internally. >>>> >>>> IOW there really being 2 differently tuned balance-profiles is not visible to >>>> the OS at all, this is handled internally inside the EC, correct ? >>>> >>> >>> No - on Lenovo's platform there are 6 different profiles that can be selected >>> from the kernel driver. 3 are intended for use on battery, 3 are intended for >>> use on AC. >> >> Ah, I already got that feeling from the rest of the thread, so I reread >> Mark's RFC again before posting my reply today and the RFC looked like >> the same 3 profiles were being set and the only functionality added >> was auto profile switching when changing between AC/battery. >> >> Thank you for clarifying this. Having 6 different stories >> indeed is a very different story. > > Apologies if I wasn't clear. I was trying to come up with a design that > took advantage of the AMD platforms have 6 settings, but was extensible > generally to other situations. > > I will redo the patches and add the thinkpad_acpi on top - that will > help it be clearer. >> >>>> Otherwise I would expect the kernel internal driver API to also change and >>>> to also see a matching thinkpad_acpi patch in the RFC series? >>> >>> The idea I see from Mark's thread was to send out RFC change for the platform profile >>> and based on the direction try to implement the thinkpad-acpi change after that. >>> >>> Because of the confusion @Mark I think you should send out an RFC v2 with thinkpad acpi >>> modeled on top of this the way that you want. >> >> I fully agree and since you introduce the concept of being on AC/battery to the >> drivers/acpi/platform_profile.c cpde, please change the >> profile_set and profile_get function prototypes in struct platform_profile_handler >> to also take a "bool on_battery" extra argument and use that in the thinkpad >> driver to select either the ac or the battery tuned low/balanced/performance >> profile. > > OK - I was thinking that, but I also figured the thinkpad driver could > get the power status directly so it was largely redundant (and saves churn > on all the other platform profile drivers - there are quite a few now) If we get the power-status in 2 places things could get out of sync, there could be unexpected race conditions, etc. Better to do just do it in one place and pass the result along. >> And please also include an update to Documentation/ABI/testing/sysfs-platform_profile >> in the next RFC. > Absolutely - that was intended. My aim with this RFC was to get feedback > on if it was acceptable or not, and if the design had to change. Really > appreciate all the good points. > >> >> Also notice how I've tried to consistently use AC/battery in my last reply, >> DC really is not a good term for "on battery". AC also is sort of dubious >> for "connected to an external power-supply" but its use for that is sorta >> common and it is nice and short. >> >> Sorry if this seems like bikeshedding, but using DC for "on battery" just >> feels wrong to me. > Ack - and I'm good with the suggestion. > >> >> >>>>> The biggest use case I can think of is that a user wants performance >>>>> when plugged in and power-save when unplugged; and they want that to >>>>> happen automatically. >>>> >>>> Right, so this what I have understood all along and I'm not disagreeing >>>> that this is a desirable feature, but it _does not belong in the kernel_! >>>> >>>> Also taking Mario's remark about the EC-firmware using differently >>>> tuned balanced profiles based on ac vs dc, here is how I envision this >>>> working: >>>> >>>> 1. Laptop is connected to charger >>>> 2. EC notices this and: >>>> 2.1 Internally switches from balanced-dc settings to balanced-ac settings >>>> 2.2 Sends out an event about the laptop now being on AC, which the kernel >>>> picks up and then sends to userspace (this already happens) >>>> 3. Userspace, e.g. power-profiles-daemon, gets the event that the laptop is >>>> now an AC and in its settings sees that the user wants to switch to >>>> performance mode on AC and uses the platform_api in its current form to >>>> ask for a switch to performance mode >>>> 4. The EC gets a command telling it to switch to performance mode and >>>> switches to the ac-tuned version of performance mode since the laptop is >>>> on ac. >>>> >>> >>> None of this happens internally on the EC. >> >> Ack, I understand now thank you for clarifying this. > Sorry for not being clear here > >> >>> Also there is nothing in this design >>> that guarantees it needs to be EC driven profile changes. It could be other >>> mailboxes, ASL code, SMM etc. >>> >>> The key point here is that thinkpad acpi has 3 AC and 3 DC profiles to choose from, >>> so some level from thinkpad acpi above needs to pick among them. >> >> Ack. >> > I think this is what makes having the design in the kernel more important. > > I understand the keeping the kernel small, but the thinkpad_acpi driver > needs to guarantee it knows it will get the notification. Without that I > don't think I can implement the feature reliably > > An alternative to the implementation is for me to do this in just the > thinkpad_acpi driver and just for PSC mode, and that's what I started > with when I looked at this (it's quite a nice simple implementation FWIW). > But I figured having something that was configurable has benefits, and > something that is applicable to all platforms is a nice feature as well. > > If doing thinkpad_acpi only would be preferred and more acceptable let > me know - but I think it's more limiting overall I believe that given the hardware interface it makes sense to handle this in the kernel; and for other platforms this will also give the option to have 2 separate profiles for ac/battery and have the kernel auto-switch, and they can just ignore the extra bool on_battery parameter to the getters/setters. Note we do still eventually need to get Rafael to weigh in and get his consent on this too. Regards, Hans
