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. > 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. 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. > 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.] I would call it acpi_execute_reg_methods() then.
