On Mon, Jan 7, 2019 at 11:32 PM Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> On Monday, January 7, 2019 2:45:14 PM CET Rafael J. Wysocki wrote:
> > On Monday, January 7, 2019 1:43:29 PM CET Rafael J. Wysocki wrote:
> > > On Mon, Jan 7, 2019 at 12:51 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > > >
> > > > ca On Sat, Jan 5, 2019 at 2:17 PM Zhang Rui <rui.zhang@xxxxxxxxx> wrote:
> > > > >
> > > > > From 6f2fac0ffcd7fd61036baa0798ab171496cff50f Mon Sep 17 00:00:00 2001
> > > > > From: Zhang Rui <rui.zhang@xxxxxxxxx>
> > > > > Date: Fri, 4 Jan 2019 14:35:52 +0800
> > > > > Subject: [PATCH] ACPI/ACPICA: Run EC _REG explicitly for ECDT
> > > > >
> > > > > commit d737f333b211 ("ACPI: probe ECDT before loading AML tables
> > > > > regardless of module-level code flag") probes ECDT before loading
> > > > > the AML tables.
> > > > >
> > > > > This is the right thing to do according to the ACPI Spec, but
> > > > > unfortunately, it breaks the current kernel EC/ECDT support, and makes
> > > > > many devices, including battery, lid, etc, fails to work on a variety
> > > > > of platforms.
> > > > >
> > > > > This is because:
> > > > > 1. Probing ECDT requires installing EC address space handler
> > > > > 2. EC _REG can not be evaluated at the time when probing ECDT because AML
> > > > > tables have not been loaded yet.
> > > > > 3. Many devices fail to work because EC _REG is not evaluated.
> > > > >
> > > > > To fix this, a solution is proposed in this patch to evaluate EC _REG
> > > > > explicitly in ACPICA, if ECDT has been probed.
> > > >
> > > > It would be good to give some more details here as the patch itself
> > > > appears to be rather convoluted.
> > > >
> > > > Also, the description above doesn't actually explain why the problem
> > > > is there, as it doesn't explain why probing the ECDT early causes the
> > > > EC _REG to be not evaluated.
> > > >
> > > > It looks like the failure is due to the change of the ordering between
> > > > acpi_load_tables() and acpi_ec_ecdt_probe() in the
> > > > acpi_gbl_group_module_level_code case which causes the EC to be probed
> > > > before instantiating the namespace and _REG obviously cannot be
> > > > evaluated then.
> > >
> > > So what happens is:
> > >
> > > acpi_ec_ecdt_probe()
> > > acpi_ec_ecdt_probe()
> > > acpi_config_boot_ec(ec, ACPI_ROOT_OBJECT, false, true)
> > > ...
> > > ec->handle = ACPI_ROOT_OBJECT;
> > > ...
> > > acpi_ec_setup(ec, false)
> > > ec_install_handlers(ec, false)
> > >
> > > acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
> > > ACPI_ADR_SPACE_EC, &acpi_ec_space_handler, NULL, ec)
> > > ...
> > > set_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)
> > >
> > > and now it returns, because handle_events is "false".
> > >
> > > Next time acpi_ec_setup() is called from acpi_ec_add() that can be
> > > invoked in two ways, either through
> > > acpi_bus_register_driver(&acpi_ec_driver) which runs it for the DSDT
> > > EC (if found), or through acpi_ec_ecdt_start() and
> > > acpi_bus_register_early_device().
> > >
> > > There are two cases in there, the acpi_config_boot_ec() one and the
> > > direct invocation of acpi_ec_setup() when acpi_is_boot_ec(ec) returns
> > > "false". The former is the failing case AFAICS, because
> > > acpi_ec_ecdt_probe() (if successful) has set boot_ec as well as
> > > ec->command_addr and ec->data_addr.
> > >
> > > So acpi_config_boot_ec() runs again and since boot_ec->handle has not
> > > been updated, it doesn't call ec_remove_handlers(), and because the
> > > EC_FLAGS_EC_HANDLER_INSTALLED is set, the address space handler
> > > installed previously is retained and _REG is not evaluated. Since it
> > > wasn't evaluated before (as it was not present then), it is never
> > > evaluated and the failure occurs.
[cut]
> it probably is better to only remove the handler in the "ECDT EC" case:
>
> ---
> drivers/acpi/ec.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/acpi/ec.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/ec.c
> +++ linux-pm/drivers/acpi/ec.c
> @@ -1637,7 +1637,18 @@ static int acpi_ec_add(struct acpi_devic
>
> if (acpi_is_boot_ec(ec)) {
> boot_ec_is_ecdt = is_ecdt;
> - if (!is_ecdt) {
> + if (is_ecdt) {
> + /*
> + * It is necessary to evaluate the _REG method for the
> + * EC address space handler, but it was not evaluated
> + * when installing that handler previously (as that
> + * happened when the namespace was not present yet), so
> + * remove the handler at this point to force the
> + * evaluation of _REG when it is installed again by
> + * acpi_config_boot_ec() below.
> + */
> + ec_remove_handlers(ec);
> + } else {
> /*
> * Trust PNP0C09 namespace location rather than
> * ECDT ID. But trust ECDT GPE rather than _GPE
>
Moreover, I think that installing the address space handler for the
ECDT EC in acpi_ec_ecdt_probe() is pointless, because AML is not
allowed to use that opregion anyway without evaluating _REG for it.
However, this opregion should be made available early, in analogy with
the "DSDT EC" case, so it looks like acpi_ec_ecdt_probe() only needs
to initialize the addresses and GPE in the ec object, set its handle
to ACPI_ROOT_OBJECT, set boot_ec to point to it and return. And
analogously for acpi_ec_dsdt_probe(). Then, acpi_ec_setup() can be
called right after acpi_ec_dsdt_probe() and it should work regardless
of the boot EC type.
Let me try to cut some patches to do that.
