Hi Bjorn, One piece of information to add: On Thu, Oct 12, 2017 at 11:27 PM, Brian Norris <briannorris@xxxxxxxxxxxx> wrote: > On Thu, Oct 12, 2017 at 10:15:23PM -0500, Bjorn Helgaas wrote: > > Is this a hole in those specs? Is this something that needs to be > > clarified by the PCI-SIG to improve interoperability? > > After re-re-reading the specifications, I'm more convinced that the > first Wifi vendor got it wrong. I also don't trust them to get many > things right in general, so this is pretty much par for the course. > > The only things I can suggest: > * "main power" is never defined, as far as I can tell. So "main" and > "auxiliary" power don't have much meaning for many M.2 cards, and so > I end up reading much of the spec with a grain of salt This part is where the first vendor seems to disagree. They claim that because power is not switched off, PERST# can remain asserted or deasserted -- whichever leads to least power consumption. (i.e., they don't consider they need to follow the parts that describe "when removing main power" (e.g., in S3) we must assert PERST#. > * S3 is never defined in the PCIe Card EM spec, but it's thrown around a > few times > * if possible, the PCIe base spec should mention something about the > fundamental reset which is expected with an L2 transition. It's not > clear what to do if you don't want to switch off power completely (and > so enter L3), but you also don't have "auxiliary" power Brian
