"On Tue, Jan 8, 2019 at 2:24 PM Zhang Rui <rui.zhang@xxxxxxxxx> wrote:
>
> On 二, 2019-01-08 at 11:15 +0100, Rafael J. Wysocki wrote:
> > 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@kerne
> > > > > l.org> wrote:
> > > > > >
> > > > > >
> > > > > > ca On Sat, Jan 5, 2019 at 2:17 PM Zhang Rui <rui.zhang@int
> > > > > > el.com> 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.
> >
> According to ACPI spec 5.2.15,
> "This optional table (ECDT) provides the processor-relative, translated
> resources of an Embedded Controller.
> The presence of this table allows OSPM to provide Embedded Controller
> operation region space access before the namespace has been evaluated."
>
> And my understanding is that the presence of ECDT means that we can
> access EC address space without _REG being evaluated, for example, by
> the module level code.
That's a good point, but I'm not sure what exactly "before the
namespace has been evaluated" means.
I think that having an opregion registered at all is only useful when
AML can run. Nothing will access the opregion before instantiating
the namespace AFAICs.
