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PM: sleep: Do not wait on SYNC_STATE_ONLY device links

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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: 05ef983e0d ("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>
This commit is contained in:
Pin-yen Lin 2025-09-26 18:23:18 +08:00 committed by Rafael J. Wysocki
parent 3ce3f56999
commit 632d31067b
3 changed files with 6 additions and 3 deletions
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1
drivers/base/base.h
View File

@ -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);

2
drivers/base/core.c
View File

@ -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;
}

6
drivers/base/power/main.c
View File

@ -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);