ACPI: PM: s2idle: Add module parameter for LPS0 constraints checking

Commit 32ece31db4df ("ACPI: PM: s2idle: Only retrieve constraints when
needed") attempted to avoid useless evaluation of LPS0 _DSM Function 1
in lps0_device_attach() because pm_debug_messages_on might never be set
(and that is the case on production systems most of the time), but it
turns out that LPS0 _DSM Function 1 is generally problematic on some
platforms and causes suspend issues to occur when pm_debug_messages_on
is set now.

In Linux, LPS0 _DSM Function 1 is only useful for diagnostics and only
in the cases when the system does not reach the deepest platform idle
state during suspend-to-idle for some reason.  If such diagnostics is
not necessary, evaluating it is a loss of time, so using it along with
the other pm_debug_messages_on diagnostics is questionable because the
latter is expected to be suitable for collecting debug information even
during production use of system suspend.

For this reason, add a module parameter called check_lps0_constraints
to control whether or not the list of LPS0 constraints will be checked
in acpi_s2idle_prepare_late_lps0() and so whether or not to evaluate
LPS0 _DSM Function 1 (once) in acpi_s2idle_begin_lps0().

Fixes: 32ece31db4df ("ACPI: PM: s2idle: Only retrieve constraints when needed")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Link: https://patch.msgid.link/2827214.mvXUDI8C0e@rafael.j.wysocki

diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
index 2a9edb53d5d453df926fe6a961db2f85a6b98724..cc3c83e4cc23b9f65f6ea1926903484fc402cf1c 100644 (file)
--- a/drivers/acpi/x86/s2idle.c
+++ b/drivers/acpi/x86/s2idle.c
@@ -28,6 +28,10 @@ static bool sleep_no_lps0 __read_mostly;
 module_param(sleep_no_lps0, bool, 0644);
 MODULE_PARM_DESC(sleep_no_lps0, "Do not use the special LPS0 device interface");
 
+static bool check_lps0_constraints __read_mostly;
+module_param(check_lps0_constraints, bool, 0644);
+MODULE_PARM_DESC(check_lps0_constraints, "Check LPS0 device constraints");
+
 static const struct acpi_device_id lps0_device_ids[] = {
        {"PNP0D80", },
        {"", },
@@ -515,7 +519,7 @@ static struct acpi_scan_handler lps0_handler = {
 
 static int acpi_s2idle_begin_lps0(void)
 {
-       if (lps0_device_handle && !sleep_no_lps0 && pm_debug_messages_on &&
+       if (lps0_device_handle && !sleep_no_lps0 && check_lps0_constraints &&
            !lpi_constraints_table) {
                if (acpi_s2idle_vendor_amd())
                        lpi_device_get_constraints_amd();
@@ -540,7 +544,7 @@ static int acpi_s2idle_prepare_late_lps0(void)
        if (!lps0_device_handle || sleep_no_lps0)
                return 0;
 
-       if (pm_debug_messages_on)
+       if (check_lps0_constraints)
                lpi_check_constraints();
 
        /* Screen off */