[RFC v1 4/8] acpi/x86: s2idle: add support for querying runtime standby state support

[Antheas Kapenekakis <lkml@antheas.dev>]

Implement the platform_s2idle_ops->get_standby_states() callback to
query which modern standby states are supported by the platform based
on the dsm func masks and expose those to the kernel as runtime standby
states. Union the vendor specific AMD/Intel masks with the ones from
Microsoft as some laptops implement both of them.

Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
 drivers/acpi/x86/s2idle.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
index 1f13c8b0ef83..08fa7841a484 100644
--- a/drivers/acpi/x86/s2idle.c
+++ b/drivers/acpi/x86/s2idle.c
@@ -513,6 +513,40 @@ static struct acpi_scan_handler lps0_handler = {
 	.attach = lps0_device_attach,
 };
 
+static u8 acpi_s2idle_get_standby_states(void)
+{
+	u8 states = 0;
+
+	if (!lps0_device_handle || sleep_no_lps0)
+		return 0;
+
+	if (lps0_dsm_func_mask_microsoft > 0) {
+		states |= BIT(PM_STANDBY_ACTIVE);
+		if (lps0_dsm_func_mask_microsoft &
+		    (1 << ACPI_LPS0_DISPLAY_OFF | 1 << ACPI_LPS0_DISPLAY_ON))
+			states |= BIT(PM_STANDBY_INACTIVE);
+		if (lps0_dsm_func_mask_microsoft &
+		    (1 << ACPI_LPS0_SLEEP_ENTRY | 1 << ACPI_LPS0_SLEEP_EXIT))
+			states |= BIT(PM_STANDBY_SLEEP);
+	}
+
+	if (lps0_dsm_func_mask > 0) {
+		states |= BIT(PM_STANDBY_ACTIVE);
+		if (acpi_s2idle_vendor_amd()) {
+			if (lps0_dsm_func_mask &
+			    (1 << ACPI_LPS0_DISPLAY_OFF_AMD |
+			     1 << ACPI_LPS0_DISPLAY_ON_AMD))
+				states |= BIT(PM_STANDBY_INACTIVE);
+		} else {
+			if (lps0_dsm_func_mask & (1 << ACPI_LPS0_DISPLAY_OFF |
+						  1 << ACPI_LPS0_DISPLAY_ON))
+				states |= BIT(PM_STANDBY_INACTIVE);
+		}
+	}
+
+	return states;
+}
+
 static int acpi_s2idle_begin_lps0(void)
 {
 	if (pm_debug_messages_on && !lpi_constraints_table) {
@@ -629,6 +663,7 @@ static void acpi_s2idle_restore_early_lps0(void)
 }
 
 static const struct platform_s2idle_ops acpi_s2idle_ops_lps0 = {
+	.get_standby_states = acpi_s2idle_get_standby_states,
 	.begin = acpi_s2idle_begin_lps0,
 	.prepare = acpi_s2idle_prepare,
 	.prepare_late = acpi_s2idle_prepare_late_lps0,
-- 
2.52.0