From mboxrd@z Thu Jan 1 00:00:00 1970 From: kai.heng.feng@canonical.com (Kai-Heng Feng) Date: Thu, 25 Jul 2019 22:02:37 +0800 Subject: [Regression] Commit "nvme/pci: Use host managed power state for suspend" has problems In-Reply-To: <2332799.izEFUvJP67@kreacher> References: <2332799.izEFUvJP67@kreacher> Message-ID: Hi Rafael, at 17:51, Rafael J. Wysocki wrote: > Hi Keith, > > Unfortunately, > > commit d916b1be94b6dc8d293abed2451f3062f6af7551 > Author: Keith Busch > Date: Thu May 23 09:27:35 2019 -0600 > > nvme-pci: use host managed power state for suspend > > doesn't universally improve things. In fact, in some cases it makes > things worse. > > For example, on the Dell XPS13 9380 I have here it prevents the processor > package > from reaching idle states deeper than PC2 in suspend-to-idle (which, of > course, also > prevents the SoC from reaching any kind of S0ix). > > That can be readily explained too. Namely, with the commit above the > NVMe device > stays in D0 over suspend/resume, so the root port it is connected to also > has to stay in > D0 and that "blocks" package C-states deeper than PC2. > > In order for the root port to be able to go to D3, the device connected > to it also needs > to go into D3, so it looks like (at least on this particular machine, but > maybe in > general), both D3 and the NVMe-specific PM are needed. > > I'm not sure what to do here, because evidently there are systems where > that commit > helps. I was thinking about adding a module option allowing the user to > override the > default behavior which in turn should be compatible with 5.2 and earlier > kernels. I just briefly tested s2i on XPS 9370, and the power meter shows a 0.8~0.9W power consumption so at least I don?t see the issue on XPS 9370. Can you please provide the output of `nvme id-ctrl /dev/nvme*` and I?ll test the NVMe controller on XPS 9380. Kai-Heng > > Cheers, > Rafael