[RFC v2 10/10] acpi/x86: s2idle: Subtract delay from last DSM fire in begin delay

[Antheas Kapenekakis <lkml@antheas.dev>]

Certain devices require a small delay to settle prior to suspend after
the last DSM firmware notification. Since that notification can now be
fired by userspace, subtract the elapsed time since the last DSM call to
lower or skip the begin quirk delay.

Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
 drivers/acpi/x86/s2idle.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
index 357d6f9406dc..06f08b5a21fd 100644
--- a/drivers/acpi/x86/s2idle.c
+++ b/drivers/acpi/x86/s2idle.c
@@ -70,6 +70,7 @@ static int lps0_dsm_state;
 
 static enum hint_idle_option current_idle = HINT_IDLE_ACTIVE;
 static enum hint_idle_option presuspend_idle = HINT_IDLE_ACTIVE;
+static unsigned long idle_transition_jiffies;
 
 /* Device constraint entry structure */
 struct lpi_device_info {
@@ -507,6 +508,7 @@ static int acpi_s2idle_idle_set(struct device *dev, enum hint_idle_option idle)
 						lps0_dsm_guid_microsoft);
 
 		current_idle = HINT_IDLE_RESUME;
+		idle_transition_jiffies = jiffies;
 		return 0;
 	}
 
@@ -594,6 +596,7 @@ static int acpi_s2idle_idle_set(struct device *dev, enum hint_idle_option idle)
 		}
 	}
 
+	idle_transition_jiffies = jiffies;
 	return 0;
 }
 
@@ -694,6 +697,7 @@ static struct acpi_scan_handler lps0_handler = {
 static int acpi_s2idle_begin_lps0(void)
 {
 	struct acpi_s2idle_dev_ops *handler;
+	unsigned int elapsed;
 	int delay = 0;
 
 	if (!lps0_device_handle || sleep_no_lps0)
@@ -726,8 +730,15 @@ static int acpi_s2idle_begin_lps0(void)
 		if (handler->begin_delay && handler->begin_delay > delay)
 			delay = handler->begin_delay;
 	}
-	if (delay > 0)
-		msleep(delay);
+	if (delay > 0) {
+		elapsed = jiffies_to_msecs(jiffies - idle_transition_jiffies);
+		if (delay > elapsed) {
+			msleep(delay - elapsed);
+			acpi_handle_debug(lps0_device_handle,
+					  "Waited %d ms for begin quirk\n",
+					  delay - elapsed);
+		}
+	}
 
 	return acpi_s2idle_begin();
 }
-- 
2.53.0