[PATCH] ACPI: s2idle: Add _Ixx GPE wake indicator support

[Saranya Gopal <saranya.gopal@intel.com>]

ACPI 6.6 defines _Ixx indicator objects under \_GPE to mark GPEs that
should remain wake-enabled in s2idle without a _PRW association.
To support them, add new function acpi_setup_ixx_gpes() that looks for
_Ixx objects for all GPEs in the FADT 0/1 blocks and if it finds any, it
marks the corresponding GPE as wake-capable, in which case the GPE is
also enabled so long as it has a handler method because marking it as
wake-capable causes acpi_update_all_gpes() to skip it. Since that only
needs to be done if suspend-to-idle is enabled, make acpi_s2idle_setup()
call that new function.

For now, this is limited to x86 systems and it assumes that the GPEs
with _Ixx will not cause spurious wakeups to occur while suspended.

Signed-off-by: Saranya Gopal <saranya.gopal@intel.com>
---
 drivers/acpi/x86/s2idle.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
index b6b1dd76a06b..ac49f9e75fae 100644
--- a/drivers/acpi/x86/s2idle.c
+++ b/drivers/acpi/x86/s2idle.c
@@ -24,6 +24,31 @@
 
 #ifdef CONFIG_SUSPEND
 
+static void acpi_setup_ixx_gpes(void)
+{
+	acpi_handle gpe_root;
+	unsigned int i;
+	char gpe_nr_str[5];
+
+	if (ACPI_FAILURE(acpi_get_handle(NULL, "\\_GPE", &gpe_root)))
+		return;
+
+	for (i = 0; i <= 0xff; i++) {
+		scnprintf(gpe_nr_str, sizeof(gpe_nr_str), "_I%02X", i);
+		if (!acpi_has_method(gpe_root, gpe_nr_str))
+			continue;
+		/*
+		 * Enable the GPE if it has a handler method because marking it
+		 * as wake-capable causes acpi_update_all_gpes() to skip it.
+		 */
+		if (ACPI_FAILURE(acpi_enable_gpe_cond(NULL, i, ACPI_GPE_DISPATCH_METHOD)))
+			continue;
+		acpi_mark_gpe_for_wake(NULL, i);
+		acpi_set_gpe_wake_mask(NULL, i, ACPI_GPE_ENABLE);
+		pm_pr_dbg("ACPI: GPE 0x%02x armed for wake via %s\n", i, gpe_nr_str);
+	}
+}
+
 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");
@@ -649,6 +674,7 @@ void __init acpi_s2idle_setup(void)
 {
 	acpi_scan_add_handler(&lps0_handler);
 	s2idle_set_ops(&acpi_s2idle_ops_lps0);
+	acpi_setup_ixx_gpes();
 }
 
 int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg)
-- 
2.34.1