On Thu, Aug 4, 2022 at 3:57 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi, > > On 8/4/22 15:51, Rafael J. Wysocki wrote: > > Hi Hans, > > > > On Thu, Aug 4, 2022 at 1:57 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> Hi Rafael, > >> > >> Sorry for the slow response... > > > > No sweat. > > > >> On 7/7/22 21:31, Rafael J. Wysocki wrote: > >>> On Wed, Jul 6, 2022 at 10:26 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >>>> > >>>> Hi, > >>>> > >>>> On 7/6/22 14:37, Rafael J. Wysocki wrote: > >>>>> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > >>>>> > >>>>> acpi_ec_ecdt_probe() is called between acpi_load_tables() and > >>>>> acpi_enable_subsystem(). It passes ACPI_ROOT_OBJECT as ec->handle > >>>>> to acpi_ec_setup() and so ACPI_ROOT_OBJECT is passed to > >>>>> acpi_install_address_space_handler() via ec_install_handlers(). > >>>>> > >>>>> Next, acpi_ns_validate_handle() converts it to acpi_gbl_root_node > >>>>> which is passed to acpi_ev_install_space_handler() and the handler is > >>>>> installed for acpi_gbl_root_node. > >>>>> > >>>>> Now, acpi_gbl_root_node is passed to acpi_ev_execute_reg_methods() which > >>>>> evaluates _REG for any ACPI_ADR_SPACE_EC regions it can find in the > >>>>> namespace which should not be necessary, because the OS is expected to > >>>>> make the ECDT operation regions available before evaluating any AML, so > >>>>> in particular AML is not expected to check the evaluation of _REG before > >>>>> it accesses these operation regions (see ACPI 6.4, Section 6.5.4, > >>>>> exception 2 [1]). Doing that is also problematic, because the _REG > >>>>> methods for the ACPI_ADR_SPACE_EC regions may depend on various _INI, so > >>>>> they should be be evaluated before running acpi_initialize_objects() [2]. > >>>>> > >>>>> Address this problem by modifying acpi_install_address_space_handler() > >>>>> to avoid evaluating _REG for ACPI_ADR_SPACE_EC regions when the handler > >>>>> is installed for acpi_gbl_root_node which indicates the ECDT case. > >>>>> > >>>>> However, this needs to be accompanied by an EC driver change to > >>>>> actually trigger the evaluation of _REG for the ACPI_ADR_SPACE_EC > >>>>> regions when it finds the EC object in the namespace. > >>>>> > >>>>> Link: https://uefi.org/specs/ACPI/6.4/06_Device_Configuration/Device_Configuration.html#reg-region # [1] > >>>>> Link: https://github.com/acpica/acpica/pull/786 # [2] > >>>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > >>>>> --- > >>>>> > >>>>> Note: This change doesn't make any practical difference on any of the systems > >>>>> in my office. > >>>>> > >>>>> --- > >>>>> drivers/acpi/acpica/evxfregn.c | 12 ++++++++++++ > >>>>> drivers/acpi/ec.c | 7 +++++++ > >>>>> 2 files changed, 19 insertions(+) > >>>>> > >>>>> Index: linux-pm/drivers/acpi/ec.c > >>>>> =================================================================== > >>>>> --- linux-pm.orig/drivers/acpi/ec.c > >>>>> +++ linux-pm/drivers/acpi/ec.c > >>>>> @@ -1632,6 +1632,13 @@ static int acpi_ec_add(struct acpi_devic > >>>>> acpi_handle_debug(ec->handle, "duplicated.\n"); > >>>>> acpi_ec_free(ec); > >>>>> ec = boot_ec; > >>>>> + /* > >>>>> + * Uninstall the EC address space handler and let > >>>>> + * acpi_ec_setup() install it again along with > >>>>> + * evaluating _REG methogs associated with > >>>>> + * ACPI_ADR_SPACE_EC operation regions. > >>>>> + */ > >>>>> + ec_remove_handlers(ec); > >>>> > >>>> This will call the _REG method to get called with ACPI_REG_DISCONNECT (0) > >>>> as second argument which may lead to unexpected consequences so I'm not > >>>> in favor of doing things this way. > >>>> > >>>> IMHO it would be much better to instead have flags; or if flags are > >>>> disliked a separate function to only call _REG later on. > >>> > >>> I'm aware of the _REG(EC, 0) part, but I thought that it might be the > >>> right thing to do. > >>> > >>> First off, I'm a bit concerned about leaving the EC address space > >>> handler attached to the root node after we have discovered the proper > >>> EC object in the namespace, because that's inconsistent with the "no > >>> ECDT" case. > >> > >> True, but in the ECDT case the EC opregion should work anywhere > >> according to the spec, so I believe it is consistent with the spec. > > > > That's until the proper EC object is discovered, though. > > > >>> It leaves a potential problem on the table too, because acpi_ec_add() > >>> changes boot_ec->handle from ACPI_ROOT_OBJECT to ec->handle and if > >>> ec_remove_handlers() is called for it after that, it will fail to > >>> remove the handler, but it will clear the > >>> EC_FLAGS_EC_HANDLER_INSTALLED flag (so the change above is actually > >>> incorrect, because it should remove the handler before changing > >>> boot_ec->handle). > >> > >> You are right, but this can be fixed by keeping track of the handle > >> used when registering the handler, e.g. something like this: > >> > >> From fceb436703bc8f0e29b7613246a83c039b631cb4 Mon Sep 17 00:00:00 2001 > >> From: Hans de Goede <hdegoede@xxxxxxxxxx> > >> Date: Thu, 4 Aug 2022 13:38:35 +0200 > >> Subject: [PATCH] ACPI: EC: Fix EC address space handler unregistration > >> > >> When an ECDT table is present the EC address space handler gets registered > >> on the root node. So to unregister it properly the unregister call also > >> must be done on the root node. > >> > >> Store the ACPI handle used for the acpi_install_address_space_handler() > >> call and use te same handle for the acpi_remove_address_space_handler() > >> call. > >> > >> Reported-by: Rafael J. Wysocki <rafael@xxxxxxxxxx> > >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > >> --- > >> drivers/acpi/ec.c | 4 +++- > >> drivers/acpi/internal.h | 1 + > >> 2 files changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c > >> index 1e93677e4b82..6aa8210501d3 100644 > >> --- a/drivers/acpi/ec.c > >> +++ b/drivers/acpi/ec.c > >> @@ -1483,6 +1483,7 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device, > >> return -ENODEV; > >> } > >> set_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags); > >> + ec->address_space_handler_handle = ec->handle; > >> } > >> > >> if (call_reg && !test_bit(EC_FLAGS_EC_REG_CALLED, &ec->flags)) { > >> @@ -1543,7 +1544,8 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device, > >> static void ec_remove_handlers(struct acpi_ec *ec) > >> { > >> if (test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) { > >> - if (ACPI_FAILURE(acpi_remove_address_space_handler(ec->handle, > >> + if (ACPI_FAILURE(acpi_remove_address_space_handler( > >> + ec->address_space_handler_handle, > >> ACPI_ADR_SPACE_EC, &acpi_ec_space_handler))) > >> pr_err("failed to remove space handler\n"); > >> clear_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags); > >> diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h > >> index 628bf8f18130..140af11d0c39 100644 > >> --- a/drivers/acpi/internal.h > >> +++ b/drivers/acpi/internal.h > >> @@ -173,6 +173,7 @@ enum acpi_ec_event_state { > >> > >> struct acpi_ec { > >> acpi_handle handle; > >> + acpi_handle address_space_handler_handle; > >> int gpe; > >> int irq; > >> unsigned long command_addr; > >> -- > > > > This works. > > > > I would rename address_space_handler_handle to something like > > address_space_handler_holder. > > Ok, I'll rename this for the official upstream submission. > > >> This fixes ec_remove_handlers() without requiring (IMHO) risky changes > >> where we call _REG() multiple times. > >> > >> Also note that ec_remove_handlers() is only ever called from > >> acpi_ec_driver.remove which in practice never runs since the EC never > >> gets hot unplugged (arguably the entire remove code could be removed). > > > > Indeed. > > > >>> But in order to move the EC address space handler under the EC object, > >>> it needs to be uninstalled and for this purpose AML needs to be told > >>> that it's not there, so evaluating _REG(EC, 0) seems reasonable to me > >>> even though I agree that it is somewhat risky. > >> > >> I'm pretty worried that calling _REG(EC, 0) will cause problems > >> the _REG handlers run pretty early on and various BIOS/ACPI table > >> authors seem to (ab)use this to do some sort of early setup > >> of some things in _REG, That is pretty much how this whole thread > >> has started. Given all the weirdness some ACPI tables do in their > >> _REG handling running _REG 3 times: > >> > >> 1. _REG(EC, 1) > >> 2. _REG(EC, 0) > >> 3. _REG(EC, 1) > >> > >> really seems like a bad idea to me. I have the feeling that this is > >> asking for trouble. > > > > OK, fair enough. > > > >>> Second, the spec is kind of suggesting doing it (cf. the "These > >>> operation regions may become inaccessible after OSPM runs > >>> _REG(EmbeddedControl, 0)" comment in the _REG definition section). > >> > >> That is boilerplate documentation copy and pasted from all the > >> other address space handlers the spec defines. I'm not sure if > >> Windows ever actually calls _REG(EmbeddedControl, 0) and I would > >> not be surprised if Windows does not do this. > >> > >>> Moreover, I don't quite like the ACPI_NO_INSTALL_SPACE_HANDLER flag, > >>> because it causes the "handler installation" to actually do something > >>> else. > >> > >> As mentioned before (IIRC) I would be more then happy to respin both > >> the ACPICA as well as the Linux ACPI bits to introduce / use 2 new > >> functions for this, lets say: > >> > >> 1. acpi_install_address_space_handler_no__reg() > > > > So we need this in ACPICA, because it doesn't make sense to drop and > > re-acquire the namespace mutex around _REG evaluation in the non-EC > > case. > > Right, just like the flags changes in this RFC getting this fixed > will require some work on the ACPICA side + then Linux changes > using the new ACPICA functions. > > > But as stated before I would prefer to introduce an > > acpi_install_address_space_handler_internal() taking an additional > > BOOL run__reg argument and I would define > > acpi_install_address_space_handler() and the new > > acpi_install_address_space_handler_no__reg() as wrappers around it. > > Right, that is how it will look like inside ACPICA, but API consumers > will just see a new acpi_install_address_space_handler_no__reg() > getting introduced. Well, one more thing about it. This would be a very generic interface with a very specific use case. Moreover, the use case in question is already detectable in acpi_install_address_space_handler(). Namely, the _REG evaluation can be skipped automatically if an ACPI_ADR_SPACE_EC handler is installed at the root of the ACPI namespace (because it doesn't even make sense to evaluate _REG then). If this is done, we don't need the extra argument. Hmm? > > > >> 2. acpi_run_address_space_handler__reg() > > > > So this would just be a wrapper around acpi_ev_execute_reg_methods() > > that would acquire the namespace mutex around it, right? [I think > > that it should also acquire acpi_gbl_namespace_rw_lock along the lines > > of acpi_walk_namespace(), though.] > > Ack. > > > I would call it acpi_execute_reg_methods() then. > > acpi_execute_reg_methods() works for me. > > I'll try to prepare a new ACPICA pull-req with the discussed > changes + a Linux series on top sometime the coming few weeks. > > Regards, > > Hans >
