Hi, I have been unable to work on this for the past few weeks, first I got sick, then I had lots of other things I was behind on because of the sickness, then my main computer that I develop on (not the toshiba) broke, and got a motherboard replacement (under warranty), but then the refurbished replacement was faulty in a different way, and I'm currently waiting for replacement of that one. Plus I now have a lot of deadlines that I'm behind on because of that. In summary: I have no idea when I will have time to look at the Toshiba again. I *do* want to get back to it eventually, but don't hold your breath. I do agree with your letter below though, once I get to that stuff. I have added some comments. On 2022-10-24 13:23, Hans de Goede wrote: > Hi Arvid, > > On 10/7/22 14:51, Arvid Norlander wrote: >> On 2022-10-07 13:22, Hans de Goede wrote: >>> Hi Arvid, >>> >>> On 10/6/22 23:12, Arvid Norlander wrote: >>>> Hi Hans, >>>> >>>> Two things: >>>> * I have discovered that reading the fan RPM in toshiba_acpi is slow, >>>> around 50 ms. I didn't notice it at first, but after adding some more >>>> sensors I found (current and voltage for AC and battery) it started to >>>> make running "sensors" visibly slow. >>>> >>>> I don't know what proper fix to this would be. Feel free to revert the >>>> fan RPM for now if it is not acceptable for reading sensors to block for >>>> ~50 ms (as opposed to the 100s of micro-seconds that other sensors such >>>> as coretemp and acpitz take to read on that laptop). >>> >>> Hmm, so apparently the single ACPI call this ends up making takes along time. >>> >>> I wonder what happens with the CPU load if you cat the file from >>> a "while true; do cat /sys/class/hwmon/...; done" loop in the shell. >>> >>> With some luck most of that 50 ms is sleeping, so we won't see say >>> 25% load on a quad core CPU (so 100% load on 1 core) in "top". >> >> After testing, thankfully it seems to be the case that it is mostly >> sleeping! > > That is good, still unfortunate that it takes so long though. > >> >>> >>> Regardless we also want any desktop-environment sensor applets which >>> poll more then once/second to block on this all the time. What most hwmon >>> drivers with slow HW access do is update the readings once per second >>> and then return cached values for a second see e.g. : >>> >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/hwmon/f71882fg.c >>> >>> and then specifically the "bool valid;" and "unsigned long last_updated; /* In jiffies */" >>> members of "struct f71882fg_data" and how those are used. >>> >>> I believe that keeping the fan rpm reading, which IMHO is the most >>> useful one is fine when adding the caching; or alternatively you >>> can submit a revert. >> >> I will try to look into this, hopefully this weekend, though I'm currently >> down with a nasty cold, so I can't promise anything. >> >>> As for the AC + bat voltage/current can those be / are those retreived >>> with the same tci_raw() call or do those require separate calls ? >>> And if they require separate calls do those calls also all take 50 ms? >> >> These are separate: A shared one for AC current and AC voltage, and two >> separate ones for battery current and battery voltage. There is also >> more data in the AC reply one that I can't quite decode, but it seems to >> be thermally related (but I have not managed to decode it as a temperature >> that matches anything else). Annoyingly the windows software displays >> almost everything in percentages on dial gauges without any units or even >> scales, making actually figuring out the interpretations rather difficult >> at times. >> >> For reading the power a call is can be issued to set the time resolution, >> in powers of two between 1 and 16 (i.e. 1, 2, 4, 8 and 16 are valid values), >> where 1 is slightly more than one new reading per second, while 16 is about >> one reading every 20ish seconds. >> >> This suggests that the EC would be updating some periodic registers >> internally and we are just querying them, however, these are still just as >> slow to read as the fan. > > Hmm, I'm not sure what is the best thing to do here, if we end up making > 4 calls of each 50 ms here, then that is going to block the caller for > 200 ms which I guess might be just acceptable if we do it only once > per x seconds, for some value of x... > > I guess you could use power_supply_is_system_supplied() to skip > the AC readings when not charging, but that ends up calling _PSR > on the ACPI AC device, which might also be slow. Is that what provides the value to /sys/class/power_supply/ADP1/online ? Because that appears to be quite fast. I have since discovered that there seems to be another way to read these (and some other) values that the Windows software uses sometimes, which I *believe* to be basically a an async request and poll for completion approach. However these calls do not appear to be that much faster when I try them, so I'm having trouble seeing the point of it (maybe it makes more difference on some other model?). Finally it doesn't fit the Linux HWMON API, which is a blocking read API. The traces basically look like: 1. Please load value -> OK 2. Is it done yet? -> No 3. Is it done yet? -> Yes, here is the value. Though usually it is done by point 2 already. The API itself for this is rather strange, my best guess is: {HCI_GET, async_register_id, normal_param1, normal_param2, normal_register_id, flag for load/check for completion} There are several such async register IDs (0xa1, 0xa7, 0xa8, ...), but each async register only accepts a (sometimes overlapping) subset of normal registers. In summary it seems quite painful to use, for very little gain given that the userspace API is blocking anyway. Thus I did not spend a large amount of time on figuring out or documenting the details of this feature. I know enough now to figure out how to do the equivilent non-async call when I see async calls in the traces. > > >> >>> >>> The battery values should already be available in some form under >>> /sys/class/power_supply/BAT* although you may only have the >>> multiplied value of the 2 there in the form of energy_now. >> >> I do seem to have voltage_now and power_now. So current could be computed >> by measuring the delta of energy_now over time and then using the voltage >> to compute the current. >> >> However, the voltage as reported in /sys/class/power_supply/BAT1 does not >> quite match the voltage I get from the HCI calls. The HCI call consistently >> reads higher, but how much higher depends on if the AC is connected or not. >> Also voltage_now seems to update rather more slowly than the HCI calls. >> >>> >>> And the AC values are nice to have but not super interesting, >>> so if they require another slow tci_raw() call then I'm not sure >>> if they are worth adding. >> >> Yes they are slow, but they might be interesting in order to compute >> system power usage while on AC (AC power - battery power) as it reports >> the battery charging current while charging and the discharging current >> while discharging. >> >> At the very least I will be documenting them when I get time. > > Yes that sounds like a good idea. I guess you could also add support > for them in the driver, but then maybe activated with some "extended_hwmon" > kernel-module option. Which then should default to off I guess? That seems like a good idea. > > Regards, > > Hans > Best regards, Arvid Norlander
