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Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Danilo Krummrich , Saravana Kannan Cc: linux-kernel@vger.kernel.org, Hsin-Te Yuan , Chen-Yu Tsai , linux-pm@vger.kernel.org, Pin-yen Lin Subject: [PATCH v4] PM: sleep: Don't wait for SYNC_STATE_ONLY device links Date: Fri, 26 Sep 2025 18:23:18 +0800 Message-ID: <20250926102320.4053167-1-treapking@chromium.org> X-Mailer: git-send-email 2.51.0.536.g15c5d4f767-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Device links with DL_FLAG_SYNC_STATE_ONLY should not affect suspend and resume, and functions like device_reorder_to_tail() and device_link_add() doesn't try to reorder the consumers with such flag. However, dpm_wait_for_consumers() and dpm_wait_for_suppliers() doesn't check this 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 =3D "usb-a-connector"; port { usb_a_con: endpoint { remote-endpoint =3D <&usb_hs>; }; }; }; usb_host { compatible =3D "mediatek,mt8186-xhci", "mediatek,mtk-xhci"; port { usb_hs: endpoint { remote-endpoint =3D <&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. Export device_link_flag_is_sync_state_only() and use it to check this in dpm_wait_for_consumers() and dpm_wait_for_suppliers() to fix this. Fixes: 05ef983e0d65a ("driver core: Add device link support for SYNC_STATE_= ONLY flag") Signed-off-by: Pin-yen Lin --- Changes in v4: - Remove inline for device_link_flag_is_sync_state_only() Changes in v3: - Squash to one patch and fix the export approach Changes in v2: - Update commit message - Use device_link_flag_is_sync_state_only() drivers/base/base.h | 1 + drivers/base/core.c | 2 +- drivers/base/power/main.c | 6 ++++-- 3 files changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/base/base.h b/drivers/base/base.h index 123031a757d9..80415b140ce7 100644 --- 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); =20 diff --git a/drivers/base/core.c b/drivers/base/core.c index d22d6b23e758..a54ec6df1058 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -287,7 +287,7 @@ static bool device_is_ancestor(struct device *dev, stru= ct 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) =3D=3D DL_FLAG_SYNC_STATE_ONLY; } diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index 2ea6e05e6ec9..73a1916170ae 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -282,7 +282,8 @@ static void dpm_wait_for_suppliers(struct device *dev, = bool async) * walking. */ list_for_each_entry_rcu_locked(link, &dev->links.suppliers, c_node) - if (READ_ONCE(link->status) !=3D DL_STATE_DORMANT) + if (READ_ONCE(link->status) !=3D DL_STATE_DORMANT && + !device_link_flag_is_sync_state_only(link->flags)) dpm_wait(link->supplier, async); =20 device_links_read_unlock(idx); @@ -339,7 +340,8 @@ static void dpm_wait_for_consumers(struct device *dev, = bool async) * unregistration). */ list_for_each_entry_rcu_locked(link, &dev->links.consumers, s_node) - if (READ_ONCE(link->status) !=3D DL_STATE_DORMANT) + if (READ_ONCE(link->status) !=3D DL_STATE_DORMANT && + !device_link_flag_is_sync_state_only(link->flags)) dpm_wait(link->consumer, async); =20 device_links_read_unlock(idx); --=20 2.51.0.536.g15c5d4f767-goog