Günter, On Sun, 10 Oct 2021 at 16:33, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > Why do you believe they are more reliable? How does it cover more motherboards? > > > > You said yourself below: "I know the naive reading from the ACPI EC registers > leads to problems (fans get stuck, etc.)". I also know what the WMI functions (BREC, RSIO, WSIO, RHWM, ) do, as I see their source. They lock the mutex (\AMW0.ASMX) and through multi-level mapping access EC or Super I/O chip registers. I know all the hardware access WMI functions begin with acquiring the same mutex, and those accessing the SIO acquire one more mutex (\_SB.PCI0.SBRG.SIO1.MUT0). Thus locking the same mutex and accessing the hardware directly is safe. By naive I meant reading EC registers without acquiring the ACPI mutex. > Something in the WMI code is obviously broken and, ultimately, will need > to get fixed. I don't know if that something is on the ASUS side or on the > kernel side, or on the interface between the two. A single WMI call taking > 1 second is way too long and strongly suggests that some timeout is involved. > Not using WMI because of that just seems wrong. On that machine a single reading of the EC register (i.e. a call to ec_read()) takes approx. 14 ms. The timeout is probably right here. >From that the 990 ms delay of BREC is understandable, because for each register it performs 4 EC transactions: read current bank, unconditionally switch current bank, read register, switch to the old bank. When I ask it to read 14 registers, it needs 42 ec_transaction() calls which would sum up to 600 ms alone. In the new approach I switch EC banks only when needed (currently only 2 times including rollback to the previous bank) and save a lot of ec_transaction() calls. It would help, however, to extend the EC interface in the acpi/ec.c to allow for block reads in a single transaction. I don't know why ec_transaction() takes so long, but in any case the API of the WMI BREC function dictates it to perform slowly because it needs to do a bank switch for each item in the input array, while the direct reading allows us to avoid that bloating. Regards, Eugene
