Re: [PATCH] ACPI/ACPICA: Run EC _REG explicitly for ECDT

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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.
> > 
> > So it looks like clearing ec-> handle before invoking
> > acpi_config_boot_ec() in the is_ecdt case in acpi_ec_add() can help,
> > can't it?
> 
> Well, that wouldn't work, because ec->handle is checked by acpi_config_boot_ec()
> too.  What might work would be to clear it and then pass the original to
> acpi_config_boot_ec() as 'handle'.  Anyway, the patch below should cover
> all of the different cases just fine, so can you try this one, please?
> 
> ---
>  drivers/acpi/ec.c |   11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> Index: linux-pm/drivers/acpi/ec.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/ec.c
> +++ linux-pm/drivers/acpi/ec.c
> @@ -1545,12 +1545,13 @@ static int acpi_config_boot_ec(struct ac
>  	int ret;
>  
>  	/*
> -	 * Changing the ACPI handle results in a re-configuration of the
> -	 * boot EC. And if it happens after the namespace initialization,
> -	 * it causes _REG evaluations.
> +	 * It is necessary to evaluate the _REG method for the EC address space
> +	 * handler, but it might not be evaluated when installing that handler
> +	 * previously (as that might happen 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_ec_setup() below.
>  	 */
> -	if (boot_ec && boot_ec->handle != handle)
> -		ec_remove_handlers(boot_ec);
> +	ec_remove_handlers(ec);
>  
>  	/* Unset old boot EC */
>  	if (boot_ec != ec)

On a second thought, this may cause _REG to be executed twice in a row
for the EC address space (in the DSDT boot EC case), so 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




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