PM: sleep: Do not wait on SYNC_STATE_ONLY device links

Device links with DL_FLAG_SYNC_STATE_ONLY should not affect system
suspend and resume, and functions like device_reorder_to_tail() and
device_link_add() don't try to reorder the consumers with that flag.

However, dpm_wait_for_consumers() and dpm_wait_for_suppliers() don't
check thas flag before triggering dpm_wait(), leading to potential hang
during suspend/resume.

This can be reproduced on MT8186 Corsola Chromebook with devicetree like:

usb-a-connector {
        compatible = "usb-a-connector";
        port {
                usb_a_con: endpoint {
                        remote-endpoint = <&usb_hs>;
                };
        };
};

usb_host {
        compatible = "mediatek,mt8186-xhci", "mediatek,mtk-xhci";
        port {
                usb_hs: endpoint {
                        remote-endpoint = <&usb_a_con>;
                };
        };
};

In this case, the two nodes form a cycle and a SYNC_STATE_ONLY devlink
between usb_host (supplier) and usb-a-connector (consumer) is created.

Address this by exporting device_link_flag_is_sync_state_only() and
making dpm_wait_for_consumers() and dpm_wait_for_suppliers() use it
when deciding if dpm_wait() should be called.

Fixes: 05ef983e0d65a ("driver core: Add device link support for SYNC_STATE_ONLY flag")
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Link: https://patch.msgid.link/20250926102320.4053167-1-treapking@chromium.org
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 700aecd22fd34a9eed1ab14f7265c29676ef3e64..86fa7fbb354891bd744c259d0955a0e178149a90 100644 (file)
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -248,6 +248,7 @@ void device_links_driver_cleanup(struct device *dev);
 void device_links_no_driver(struct device *dev);
 bool device_links_busy(struct device *dev);
 void device_links_unbind_consumers(struct device *dev);
+bool device_link_flag_is_sync_state_only(u32 flags);
 void fw_devlink_drivers_done(void);
 void fw_devlink_probing_done(void);
 

diff --git a/drivers/base/core.c b/drivers/base/core.c
index d22d6b23e75898a63c91101ab7821723ca50ceb5..a54ec6df1058fbf082cf75778749ace83ccbff6b 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -287,7 +287,7 @@ static bool device_is_ancestor(struct device *dev, struct device *target)
 #define DL_MARKER_FLAGS                (DL_FLAG_INFERRED | \
                                 DL_FLAG_CYCLE | \
                                 DL_FLAG_MANAGED)
-static inline bool device_link_flag_is_sync_state_only(u32 flags)
+bool device_link_flag_is_sync_state_only(u32 flags)
 {
        return (flags & ~DL_MARKER_FLAGS) == DL_FLAG_SYNC_STATE_ONLY;
 }

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index e3a7f25bf8d39b947e08b0a5febb28a4afca28d9..c97f8b139dc202b3dd25560ad87281e21d292f72 100644 (file)
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -278,7 +278,8 @@ static void dpm_wait_for_suppliers(struct device *dev, bool async)
         * walking.
         */
        dev_for_each_link_to_supplier(link, dev)
-               if (READ_ONCE(link->status) != DL_STATE_DORMANT)
+               if (READ_ONCE(link->status) != DL_STATE_DORMANT &&
+                   !device_link_flag_is_sync_state_only(link->flags))
                        dpm_wait(link->supplier, async);
 
        device_links_read_unlock(idx);
@@ -335,7 +336,8 @@ static void dpm_wait_for_consumers(struct device *dev, bool async)
         * unregistration).
         */
        dev_for_each_link_to_consumer(link, dev)
-               if (READ_ONCE(link->status) != DL_STATE_DORMANT)
+               if (READ_ONCE(link->status) != DL_STATE_DORMANT &&
+                   !device_link_flag_is_sync_state_only(link->flags))
                        dpm_wait(link->consumer, async);
 
        device_links_read_unlock(idx);