On Tue, Jun 14, 2016 at 10:22 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > On Tue, Jun 14, 2016 at 09:14:27PM +0200, Andreas Noever wrote: >> On Tue, Jun 14, 2016 at 6:37 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: >> > [+cc linux-kernel] >> > >> > On Sat, May 21, 2016 at 11:48:42AM +0200, Andreas Noever wrote: >> >> >> >> Signed-off-by: Andreas Noever <andreas.noever@xxxxxxxxx> >> >> >> >> Tested on MacBookPro10,1 >> >> >> >> On Fri, May 13, 2016 at 1:15 PM, Lukas Wunner <lukas@xxxxxxxxx> wrote: >> >> > This series powers Thunderbolt controllers on Macs down when nothing is >> >> > plugged in, saving 1.7 W on machines with a Light Ridge controller and >> >> > reportedly 4 W on Cactus Ridge 4C and Falcon Ridge 4C. >> >> > >> >> > Briefly, a custom ACPI method provided by Apple is used to cut power to >> >> > the controller. A GPE is enabled while the controller is powered down >> >> > which side-band signals a plug event, whereupon power is reinstated using >> >> > the ACPI method. Note that even though this mechanism is ACPI-based, >> >> > it does not use _PSx methods and is thus entirely nonstandard. >> > >> > I think the current arrangement was that Andreas would ack Thunderbolt >> > patches and I would merge them via the PCI tree. That makes some sense >> > because Thunderbolt and PCIe are related, but the more I think about >> > it, the less I'm happy with it. >> > >> > This series is a good example. I'm sure it's good work and >> > worthwhile. But I can't really say anything about the content of it >> > because most of it is Thunderbolt-specific and there's no public spec. >> > It seems like this is basically a collection of reverse-engineered >> > quirks that happen to work with the current state of Linux PM on >> > certain Macs. We don't know what might change on future Macs. We >> > don't know what might break when we make changes to Linux PM. >> > >> > I can't test this series, nor do I want to. I can't test most of the >> > patches I merge, but I can at least read the spec and see whether the >> > patches make sense. What I would *like* is to have public Thunderbolt >> > specs and a kernel developer's guide so we know what to expect from >> > the hardware and the firmware and we can write code that should work >> > not just on current Macs, but also on non-Macs and future Macs. >> > >> > I don't think the current situation is really maintainable, and I'm >> > not comfortable merging code that I can't maintain. >> Most of the code is contained within the thunderbolt driver. I think >> there is quite some precedence for reverse engineered drivers without >> specs being part of the kernel. My understanding was that, since I am >> listed in MAINTAINERS, I am responsible for the driver. Now our >> changes often need improvements to the pci core, which is why I think >> merging through your tree is a good idea (without transferring >> responsibility). The changes to the drivers/pci should be supported by >> the PCI-spec and make sense without knowing about thunderbolt (but it >> might be the case that thunderbolt is the only user of these >> features). >> >> Specifically for this series we want to: >> - whitelist thunderbolt bridges for PM. Detecting those bridges is >> non-standard but I think this is acceptable, since this >> blacklist/whitelist is basically a quirk. >> - Load our portdrv on tb bridges. PCI just sees another portdriver >> and all the reverse engineered magic lives inside the driver. >> - Forward more PM callbacks to portdrivers (not tb specific) >> - hotplug D3cold fixes: resume around board_added/remove_board, >> ignore interrupts in d3cold (not tb specific and probably a general >> bugfix) >> - Make pci not fail if bridges have been put into D3cold by some >> external mechanism. >> >> So maybe you could review the pci changes as a solution to the problem >> "we want to load a custom portdriver which can put bridges into d3cold >> in a device specific way". We certainly to not expect you to take >> responsibility for the thunderbolt driver. > > That's a fine solution as far as I'm personally concerned. I think > it's poor for Linux overall, because I think it's fragile, and it's > disappointing that a technology as important as Thunderbolt is so > poorly supported by the promulgators. But if you're willing to work > in that environment, that's great. > > You maintain the thunderbolt code and merge changes, and I'll review > the pieces that touch drivers/pci. I do have a couple comments on > those pieces, but I don't think they'll be major. > > I just want to get out of the business of merging drivers/thunderbolt > code that I can't maintain. [+ Greg] Hi Greg, do you mind if we revert to the old scheme and merge TB changes through your tree? Regards, Andreas > Bjorn -- 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
