Re: How to enable auto-suspend by default

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Mon, Nov 23, 2020 at 02:54:19PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 11/11/20 3:31 PM, Mika Westerberg wrote:
> > On Wed, Nov 11, 2020 at 12:27:32PM +0100, Hans de Goede wrote:
> >> Hi,
> >>
> >> On 11/10/20 6:25 PM, Mika Westerberg wrote:
> >>> On Tue, Nov 10, 2020 at 04:02:33PM +0000, Limonciello, Mario wrote:
> >>>>>
> >>>>> On Tue, Nov 10, 2020 at 11:57:07AM +0100, Bastien Nocera wrote:
> >>>>>> Hey,
> >>>>>>
> >>>>>> systemd has been shipping this script to enable auto-suspend on a
> >>>>>> number of USB and PCI devices:
> >>>>>>
> >>>>> https://github.com/systemd/systemd/blob/master/tools/chromiumos/gen_autosuspen
> >>>>> d_rules.py
> >>>>>>
> >>>>>> The problem here is twofold. First, the list of devices is updated from
> >>>>>> ChromeOS, and the original list obviously won't be updated by ChromeOS
> >>>>>> developers unless a device listed exists in a ChromeBook computer,
> >>>>>> which means a number of devices that do support autosuspend aren't
> >>>>>> listed.
> >>>>>>
> >>>>>> The other problem is that this list needs to exist at all, and that it
> >>>>>> doesn't seem possible for device driver developers (at various levels
> >>>>>> of the stack) to opt-in to auto-suspend when all the variants of the
> >>>>>> device (or at least detectable ones) support auto-suspend.
> >>>>>
> >>>>> A driver can say they support autosuspend today, but I think you are
> >>>>> concerned about the devices that are controlled by class-compliant
> >>>>> drivers, right?  And for those, no, we can't do this in the kernel as
> >>>>> there are just too many broken devices out there.
> >>>>>
> >>>>
> >>>> I guess what Bastien is getting at is for newer devices supported by class
> >>>> drivers rather than having to store an allowlist in udev rules, can we set
> >>>> the allowlist in the kernel instead.  Then distributions that either don't
> >>>> use systemd or don't regularly update udev rules from systemd can take
> >>>> advantage of better defaults on modern hardware.
> >>>>
> >>>> The one item that stood out to me in that rules file was 8086:a0ed.
> >>>> It's listed as "Volteer XHCI", but that same device ID is actually present
> >>>> in an XPS 9310 in front of me as well and used by the xhci-pci kernel module.
> >>>>
> >>>> Given we're effectively ending up with the combination of runtime PM turned
> >>>> on by udev rules, do we need something like this for that ID:
> >>>>
> >>>> https://github.com/torvalds/linux/commit/6a7c533d4a1854f54901a065d8c672e890400d8a
> >>>>
> >>>> @Mika Westerberg should 8086:a0ed be quirked like the TCSS xHCI too?
> >>>
> >>> I think this one is the TGL PCH xHCI. The quirk currently for xHCI
> >>> controllers that are part of the TCSS (Type-C SubSystem) where it is
> >>> important to put all devices into low power mode whenever possible,
> >>> otherwise it keeps the whole block on.
> >>
> >> Note that there are currently some IDs missing from the xHCIs which
> >> are part of the TCSS too. At least the id for the xHCI in the thunderbolt
> >> controller on the Lenovo T14 gen 1 is missing. I started a discussion
> >> about extending the kernel quirk list for this vs switching to hwdb
> >> a while a go:
> >>
> >> https://lore.kernel.org/linux-usb/b8b21ba3-0a8a-ff54-5e12-cf8960651086@redhat.com/
> >>
> >> The conclusion back then was to switch to hwdb, but I never got around to this.
> > 
> > The reason I've added these to the xHCI driver is that it works even if
> > you are running some really small userspace (like busybox). Also for the
> > xHCI in TCSS we know for sure that it fully supports D3cold.
> > 
> > (The one you refer above is actually mistake from my side as I never
> >  tested Alpine Ridge LP controller which I think this is).
> 
> Ok, so I'll submit a patch adding the 15c1 product-id for the
> INTEL_ALPINE_RIDGE_LP_2C_XHCI controller to the list of ids for which we
> set the XHCI_DEFAULT_PM_RUNTIME_ALLOW quirk. To fix the much too high
> idle-power consumption problem on devices with this Alpine Ridge variant.

Thanks!