[PATCH v2 3/5] acpi/x86: s2idle: add quirk table for modern standby delays

[Antheas Kapenekakis <lkml@antheas.dev>]

Unfortunately, some modern standby systems, including the ROG Ally, rely
on a delay between modern standby transitions. Add a quirk table for
introducing delays between modern standby transitions, and quirk the
ROG Ally on "Display Off", which needs a bit of time to turn off its
controllers prior to suspending (i.e., entering DRIPS).

Reported-by: Denis Benato <benato.denis96@gmail.com>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
 include/linux/suspend.h |  5 +++++
 kernel/power/suspend.c  | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 8f33249cc067..d7e2a4d8ab0c 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -144,6 +144,11 @@ struct platform_s2idle_ops {
 	int (*display_on)(void);
 };
 
+struct platform_s2idle_quirks {
+	int delay_display_off;
+	int delay_display_on;
+};
+
 #ifdef CONFIG_SUSPEND
 extern suspend_state_t pm_suspend_target_state;
 extern suspend_state_t mem_sleep_current;
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 610f8ecaeebd..af2abdd2f8c3 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -11,6 +11,7 @@
 
 #include <linux/string.h>
 #include <linux/delay.h>
+#include <linux/dmi.h>
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/console.h>
@@ -61,6 +62,30 @@ static DECLARE_SWAIT_QUEUE_HEAD(s2idle_wait_head);
 enum s2idle_states __read_mostly s2idle_state;
 static DEFINE_RAW_SPINLOCK(s2idle_lock);
 
+// The ROG Ally series disconnects its controllers on Display Off, without
+// holding a lock, introducing a race condition. Add a delay to allow the
+// controller to disconnect cleanly prior to suspend.
+static const struct platform_s2idle_quirks rog_ally_quirks = {
+	.delay_display_off = 500,
+};
+
+static const struct dmi_system_id platform_s2idle_quirks[] = {
+	{
+		.matches = {
+			DMI_MATCH(DMI_BOARD_NAME, "RC71L"),
+		},
+		.driver_data = (void *)&rog_ally_quirks
+	},
+	{
+		.matches = {
+			DMI_MATCH(DMI_BOARD_NAME, "RC72L"),
+		},
+		.driver_data = (void *)&rog_ally_quirks
+	},
+	{}
+};
+
+
 /**
  * pm_suspend_default_s2idle - Check if suspend-to-idle is the default suspend.
  *
@@ -589,12 +614,26 @@ static int enter_state(suspend_state_t state)
 	if (state == PM_SUSPEND_TO_IDLE)
 		s2idle_begin();
 
+	/*
+	 * Windows transitions between Modern Standby states slowly, over multiple
+	 * seconds. Certain manufacturers may rely on this, introducing race
+	 * conditions. Until Linux can support modern standby, add the relevant
+	 * delays between transitions here.
+	 */
+	const struct dmi_system_id *s2idle_sysid = dmi_first_match(
+		platform_s2idle_quirks
+	);
+	const struct platform_s2idle_quirks *s2idle_quirks = s2idle_sysid ?
+		s2idle_sysid->driver_data : NULL;
+
 	/*
 	 * Linux does not have the concept of a "Screen Off" state, so call
 	 * the platform functions for Display On/Off prior to the suspend
 	 * sequence, mirroring Windows which calls them outside of it as well.
 	 */
 	platform_suspend_display_off();
+	if (s2idle_quirks && s2idle_quirks->delay_display_off)
+		msleep(s2idle_quirks->delay_display_off);
 
 	if (sync_on_suspend_enabled) {
 		trace_suspend_resume(TPS("sync_filesystems"), 0, true);
@@ -624,6 +663,8 @@ static int enter_state(suspend_state_t state)
  Unlock:
 	mutex_unlock(&system_transition_mutex);
 
+	if (s2idle_quirks && s2idle_quirks->delay_display_on)
+		msleep(s2idle_quirks->delay_display_on);
 	platform_suspend_display_on();
 	return error;
 }
-- 
2.46.1