[Public] > On 3/24/22 08:04, Limonciello, Mario wrote: > > [Public] > > > >> On Mon, Mar 21, 2022 at 11:57 PM Damien Le Moal > >> <damien.lemoal@xxxxxxxxxxxxxxxxxx> wrote: > >>> > >>> * Rename ahci_board_mobile to board_ahci_low_power to be more > >> descriptive > >>> of the feature as that is also used on PC and server AHCI adapters, > >>> from Mario. > >>> > >>> Mario Limonciello (3): > >>> ata: ahci: Rename board_ahci_mobile > >>> ata: ahci: Rename `AHCI_HFLAG_IS_MOBILE` > >>> ata: ahci: Rename CONFIG_SATA_LPM_MOBILE_POLICY configuration > item > >> > >> So I've pulled this, but it's worth noting that particularly renaming > >> that CONFIG option was probably not a good idea. > >> > >> Why? > >> > >> Because it means that people silently lose their old values. And it has that > >> > >> range 0 4 > >> default 0 > >> > >> with 4 being explicitly marked as very dangerous - but at least Fedora > >> seems to actually have a default of 3 in their kernels: > >> > >> /boot/config-5.16.13-200.fc35.x86_64: > >> CONFIG_SATA_MOBILE_LPM_POLICY=3 > >> > >> so that "default 0" may actually not be the right one. > >> > >> Now, we're at the point where few enough people likely care about ATA, > >> but the corollary to that is also that these kinds of changes can > >> cause user pain that then developers have *no* idea about. > >> Particularly when the pain ends up being caused by some subtle default > >> config option silently changing that nobody even thought about. > >> > >> Now, that "default 0" is probably the only safe default - and I don't > >> dispute that part. But I also suspect that Fedora chose that value '3' > >> because it probably makes a noticeable power use difference on at > >> least some platforms. > >> > >> I don't know. But I doubt really *anybody* knows, so renaming them and > >> silently likely changing config options for some less-than-critical > >> reason is just not a great idea. > >> > >> Linus > > > > Thanks for pointing out the subtlety of renaming a configuration option hides > > problems because people don't see the new config option and pick the default. > > I wouldn't call this configuration option rename critical, so if you chose to > revert > > it I would understand. > > > > However I think you raise a good point that if distros are picking different > "default" > > values and keeping them there a long time that the value in the upstream > kernel > > is probably not right anymore. A while back that default made sense because > all the > > power saving stuff was risky at the time. It's pretty well baked now. > > > > So maybe a logical thing is to keep this change and send a follow up that also > changes > > the default to 3? If you're supportive of that I'll send something to Damien to > do that. > > Mario, let's check what other distros do first before deciding. Fedora for > sure has a default of 3 and I have never seen any issue with it (and I > have been using Fedora for a long time with many different drives). > > Not sure what distro you are using, but if it is not Fedora, please check. > We should check at least Debian, Ubuntu, SUSE, RHEL and CentOS. I can > check some other minor ones too as I know users. > I use Ubuntu mostly, and have a variety of distro kernels installed: config-5.13.0-25-generic:CONFIG_SATA_MOBILE_LPM_POLICY=3 config-5.14.0-1029-oem:CONFIG_SATA_MOBILE_LPM_POLICY=3 config-5.4.0-60-generic:CONFIG_SATA_MOBILE_LPM_POLICY=3
