On Sunday, May 26, 2019 10:27:50 PM CEST Shaunak Saha wrote:
> In the present implementation sleep function was getting called in
> acpi_s2idle_prepare and as all the devices may not have suspended
> at that stage e.g. if we are telling ec about the S0ix then calling early
> can cause ec reply wrongly interpreted as spurious wake events.
> Here we call it at much later stage in acpi_s2idle_sync. As per the
> specification the entry _DSM function may be invoked when the OS state has
> reached sufficient criteria for processor idle state entry matching
> Entry Trigger defined in LPIT to be interpreted as a request for the
> platform to enter a Low Power S0 Idle (LPI) state. Here we are checking if
> the we reached the minimum D-State defined in the constraint function of
> the LPIT _DSM method before calling the sleep entry function. Also not
> checking for constraint in acpi_s2idle_wake anymore and also changed the
> acpi info loglevel to debug in lpi_check_constraint.
This patch does three different things, two of which are questionable and
one is done incorrectly.
First off, aborting system suspend because S0ix constraints are not met is
a non-starter. The kernel really cannot refuse to suspend the system for
that reason (and diagnostics can be done after resume anyway).
Second, according to my knowledge, it is not a bug to invoke the
ACPI_LPS0_ENTRY _DSM when the constraints are not met. Do you
actually know about any platforms where that may cause real problems
to occur?
Finally, it is too late to invoke that _DSM from acpi_s2idle_sync(), because
that is called after leaving S0ix and resuming some devices.
I can believe the claim that invoking the ACPI_LPS0_ENTRY _DSM in
acpi_s2idle_prepare() may be too early and it may confuse the EC, say,
but I'm not sure why the ACPI_LPS0_SCREEN_OFF _DSM would be
affected by that too.
So overall, the patch below may actually work, but not the $subject one
(if evaluating the ACPI_LPS0_ENTRY _DSM when the constraints are not
met is *really* problematic, it may be necessary to add the check
for that on top of it).
---
drivers/acpi/sleep.c | 13 +++++++++----
include/linux/suspend.h | 1 +
kernel/power/suspend.c | 8 ++++++--
3 files changed, 16 insertions(+), 6 deletions(-)
Index: linux-pm/drivers/acpi/sleep.c
===================================================================
--- linux-pm.orig/drivers/acpi/sleep.c
+++ linux-pm/drivers/acpi/sleep.c
@@ -967,8 +967,6 @@ static int acpi_s2idle_prepare(void)
{
if (lps0_device_handle) {
acpi_sleep_run_lps0_dsm(ACPI_LPS0_SCREEN_OFF);
- acpi_sleep_run_lps0_dsm(ACPI_LPS0_ENTRY);
-
acpi_ec_set_gpe_wake_mask(ACPI_GPE_ENABLE);
}
@@ -983,6 +981,12 @@ static int acpi_s2idle_prepare(void)
return 0;
}
+static void acpi_s2idle_sleep(void)
+{
+ if (lps0_device_handle)
+ acpi_sleep_run_lps0_dsm(ACPI_LPS0_ENTRY);
+}
+
static void acpi_s2idle_wake(void)
{
if (!lps0_device_handle)
@@ -1007,6 +1011,8 @@ static void acpi_s2idle_wake(void)
*/
acpi_ec_dispatch_gpe();
}
+
+ acpi_sleep_run_lps0_dsm(ACPI_LPS0_EXIT);
}
static void acpi_s2idle_sync(void)
@@ -1034,8 +1040,6 @@ static void acpi_s2idle_restore(void)
if (lps0_device_handle) {
acpi_ec_set_gpe_wake_mask(ACPI_GPE_DISABLE);
-
- acpi_sleep_run_lps0_dsm(ACPI_LPS0_EXIT);
acpi_sleep_run_lps0_dsm(ACPI_LPS0_SCREEN_ON);
}
}
@@ -1049,6 +1053,7 @@ static void acpi_s2idle_end(void)
static const struct platform_s2idle_ops acpi_s2idle_ops = {
.begin = acpi_s2idle_begin,
.prepare = acpi_s2idle_prepare,
+ .sleep = acpi_s2idle_sleep,
.wake = acpi_s2idle_wake,
.sync = acpi_s2idle_sync,
.restore = acpi_s2idle_restore,
Index: linux-pm/include/linux/suspend.h
===================================================================
--- linux-pm.orig/include/linux/suspend.h
+++ linux-pm/include/linux/suspend.h
@@ -190,6 +190,7 @@ struct platform_suspend_ops {
struct platform_s2idle_ops {
int (*begin)(void);
int (*prepare)(void);
+ void (*sleep)(void);
void (*wake)(void);
void (*sync)(void);
void (*restore)(void);
Index: linux-pm/kernel/power/suspend.c
===================================================================
--- linux-pm.orig/kernel/power/suspend.c
+++ linux-pm/kernel/power/suspend.c
@@ -136,10 +136,14 @@ static void s2idle_loop(void)
* so prevent them from terminating the loop right away.
*/
error = dpm_noirq_suspend_devices(PMSG_SUSPEND);
- if (!error)
+ if (!error) {
+ if (s2idle_ops && s2idle_ops->sleep)
+ s2idle_ops->sleep();
+
s2idle_enter();
- else if (error == -EBUSY && pm_wakeup_pending())
+ } else if (error == -EBUSY && pm_wakeup_pending()) {
error = 0;
+ }
if (!error && s2idle_ops && s2idle_ops->wake)
s2idle_ops->wake();
