On Thu, Dec 3, 2020 at 10:53 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi, > > On 12/2/20 8:57 PM, Rafael J. Wysocki wrote: > > On Wed, Dec 2, 2020 at 8:39 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> Hi, > >> > >> On 12/2/20 2:49 PM, Rafael J. Wysocki wrote: > >>> On Sat, Nov 21, 2020 at 9:30 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >>>> > >>>> Hi Rafael, > >>>> > >>>> A while ago (almost 2 years ago) I discussed an issue with you about > >>>> some devices, where some of the methods used during device-addition > >>>> (such as _HID) may rely on OpRegions of other devices: > >>>> > >>>> https://www.spinics.net/lists/linux-acpi/msg86303.html > >>>> > >>>> An example of this is the Acer Switch 10E SW3-016 model. The _HID method > >>>> of the ACPI node for the UART attached Bluetooth, reads GPIOs to detect > >>>> the installed wifi chip and update the _HID for the Bluetooth's ACPI node > >>>> accordingly. The current ACPI scan code calls _HID before the GPIO > >>>> controller's OpRegions are available, leading to the wrong _HID being > >>>> used and Bluetooth not working. > >>>> > >>>> Last week I bought a second hand Acer device, not knowing it was this > >>>> exact model. Since I now have access to affected hardware I decided to > >>>> take a shot at fixing this. > >>>> > >>>> In the discussion you suggested to split the acpi_bus_scan of the root > >>>> into 2 steps, first scan devices with an empty _DEP, putting other > >>>> acpi_handle-s on a list of deferred devices and then in step 2 scan the > >>>> rest. > >>>> > >>>> I'm happy to report that, at least on the affected device, this works > >>>> nicely. While working on this I came up with a less drastic way to > >>>> deal with this. As you will see in patch 4 of this series, I decided > >>>> to first add a more KISS method of deciding which devices to defer > >>>> to the second scan step by matching by HID. This has the disadvantage > >>>> of not being a generic solution. But it has the advantage of being a > >>>> solution which does not potentially regress other devices. > >>>> > >>>> Then in patch 5 I actually do add the option to defer or not based on > >>>> _DEP being empty. I've put this behind a kernel commandline option as > >>>> I'm not sure we should do this everywhere by default. At least no without > >>>> a lot more testing. > >>>> > >>>> Patch 6 fixes an issue with patch 5 which causes battery devices to stop > >>>> working. > >>>> > >>>> And patch 7 adds some extra HIDs to the list of HIDs which should be > >>>> ignored when checking if the _DEP list is empty from Linux' pov, iow > >>>> some extra HIDs which Linux does not bind to. > >>>> > >>>> Please let me know what you think about this patch-set. I would be happy > >>>> to see just patches 1-4 merged. > >>> > >>> I took patches 1 and 2, because IMO they are generally useful (I > >>> rewrote the changelogs to avoid mentioning the rest of the series > >>> though), > >> > >> That is fine. Thanks for taking those. > >> > >>> but I have some reservations regarding the rest. > >>> > >>> First off, I'm not really sure if failing acpi_add_single_object() for > >>> devices with missing dependencies is a good idea. IIRC there is > >>> nothing in there that should depend on any opregions supplied by the > >>> other devices, so it should be safe to allow it to complete. > >> > >> Actually acpi_add_single_object() does depend on ACPI methods > >> which may depend on opregions, that is the whole reason why > >> this series is necessary. Otherwise we could just delay the > >> binding of the driver based in dep_unmet which would be easier. > >> > >> Here are 2 actual examples of acpi_add_single_object() calling > >> ACPI methods which may depend on opregions: > >> > >> 1. acpi_add_single_object() calls acpi_init_device_object() which > >> calls acpi_set_pnp_ids() which fills a bunch if fields of > >> struct acpi_device with info returned by the acpi_get_object_info() > >> call. > >> > >> Specifically it stores the value returned by the _HID method in > >> the acpi_device_pnp array for the device and that _HID method is > >> actually the problem in the example device which started this > >> series. The _HID method of the bluetooth device reads 2 GPIOs > >> to get a hw-id (0-3) and then translates the hwid to a _HID > >> string. If the GPIO opregion's handlers have not registered yet > >> then the reading of the GPIOs is correctly skipped, and hwid > >> 0 is assumed, which is wrong in this case. > >> > >> 2. I've also seen examples where _STA depends on GPIOs in a similar > >> manner; and acpi_add_single_object() calls acpi_bus_get_power_flags() > >> which calls acpi_bus_init_power() which calls acpi_device_is_present() > >> which depends on _STA results. > > > > Well, this means that there is a bug in acpi_bus_attach() which > > shouldn't call acpi_bus_init_power() which has been called already. > > I'm afraid we have a bit of a misunderstanding here, the problem is > not that acpi_bus_attach() calls acpi_bus_init_power(), the problem is > that acpi_bus_init_power() (which is called from acpi_add_single_object()) > depends on the value returned by _STA and that in turn may depend on > some OpRegions being available. IOW it is the same problem as the _HID > problem. This was a side note. Arguably, acpi_bus_init_power() should not be called twice in a row for the same device, which is actually done by the current code. Another side note: while we can avoid evaluating _STA for the devices whose enumeration we want to defer, avoiding to evaluate _HID (or _CID for that matter) for them will be rather hard. > > And it all means that either deferring acpi_add_single_object() is > > needed and so there need to be 2 passes in acpi_bus_attach() overall, > > or acpi_add_single_object() needs to avoid calling methods that may > > depend on supplied opregions. I guess the latter is rather > > unrealistic, so the only practical choice is the former. > > I agree. > > > However, I still don't think that the extra list of "dependent > > devices" is needed. > > I'm not sure what you are trying to say here? Do you mean this list: > > +/* > + * List of HIDs for which we defer adding them to the second step of the > + * scanning of the root, because some of their methods used during addition > + * depend on OpRegions registered by the drivers for other ACPI devices. > + */ > +static const char * const acpi_defer_add_hids[] = { > + "BCM2E5B", /* Acer SW3-016 bluetooth HID when GPIO OpRegs or not available yet */ > + NULL > +}; > + > > ? No, the one created by patch [4/7] in your series, acpi_deferred_devices. > That indeed is not necessary if you take the entire set and always enable the > new behavior instead of using the module option. I guess we could go that route > for 5.12, and get it into next as soon as 5.11-rc1 is available for maximum > testing. > > Do you want me to do a new version of the series which drops the acpi_defer_add_hids[] > thing and the module option and simply always uses the new behavior? No, something else. Stay tuned.
