Thanks a lot for explaination, Emmanuel! Now I finally know why this is a "catch-22" situation: Disabling those features with OS/drvier cannot be as neat as disabling them directly in BIOS. And there may be chance, that disabling them at a bad timing may cause G3... -- wzyboy 2013/11/15 Emmanuel Grumbach <egrumbach@xxxxxxxxx>: > > > On 11/15/2013 05:06 AM, wzyboy wrote: >> 2013/11/15 Bjorn Helgaas <bhelgaas@xxxxxxxxxx>: >>> Why would it be unlikely to fix the driver? Do people think the >>> problem is not actually in the driver? >>> >>> Asking Lenovo how to disable L1 PM substates is really a non-answer. >>> Only the extremely technical and extremely patient user (hi wzyboy :)) >>> will even bother to investigate why wifi works fine with Windows but >>> not with Linux. The only thing Lenovo *could* do is to release a new >>> BIOS with a switch to control L1 PM Substates. If I were Lenovo, I >>> would never do that because then I would have to tell customers >>> "disable this for Linux, enable this for Windows," and I'd have to >>> deal with support calls about devices using more power than they >>> should, battery life being shorter, etc. Plus you'd have to ask every >>> Linux user to upgrade their BIOS. That's all just a terrible user >>> experience. >> >> >> I am a little confused. There are two sets of "setpci" commands, both >> of which can make me use my NIC reliably. But you two say they are >> just workarounds, not real fixes. >> > > Right - because they force a mode that the BIOS doesn't allow. The BIOS > doesn't allow the OS (the driver) to decide in what mode to work - so we > cannot reach the same effect as the setpci command from the OS / driver > level. setpci just directly accesses the HW without asking the > permissions of anyone. > >> I know the "side effect" of first two "setpci" commands is consuming >> more power. (Actually by my experience of running on battery, I did >> not notice ...) >> >> But Grumbach said after the second two "setpci" commands enables "L1". >> Does it mean it saves power? So what's the "side effect" of second two >> "setpci" commands? >> > > They are both the same in terms of side-effects. The first set of setpci > commands will disable L1 altogether - meaning you don't save any power. > The second set of setpci doesn't disable L1, but disable a more subtle > power state (actually several) which are defined as L1 PM substates. In > theses substates, you save less power than in L1 (I think) but you are > more likely to be able to reach them. After all, it is always the same > story - the deeper you sleep, you longer it takes to wake up. And if it > takes longer to wake up, it also means that in several cases you won't > chose to go to sleep. So the way PCI folks help to save power even in > case where you cannot go to a deep sleep is to define states in the > middle in which you save less power, but in which you are more likely to > be. Again - time spent in each state and power saved in each state trade > off. > Now: > L1 - deep sleep > L1 PM substate - something in the middle. > > First setpci command - disable both features. > Second setpci command - disable only the second feature. > > Regarding side effects... I don't think this is really "dangerous". But > this is not a fix in the way that I wouldn't like to deploy millions of > machines like that. The risk you have here is probably to have a bad > timing and have the setpci commands run exactly when the link is in a > state that setpci disables. That would be bad. How bad? Probably would > just require a reboot - or worst case G3 (take the battery off). > >> IMHO, if this could user use their NIC reliably, maybe Grumbach may >> write these commands to iwlwifi driver and run them when 7260 is >> detected... > > I can't as exlained above. > >> >> BTW, no replies from Lenovo, yet. >> > > >> Or maybe you could add an option, which enables this "workaround" if >> user wants. A user could simply write a /etc/modprobe.d/iwlwifi.conf >> and enable this "workaround", to use their NICs without having to >> reboot from time to time... > > same. > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
