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Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Danilo Krummrich , Saravana Kannan Cc: Hsin-Te Yuan , linux-pm@vger.kernel.org, Chen-Yu Tsai , linux-kernel@vger.kernel.org, Pin-yen Lin Subject: [PATCH v2 2/2] PM: sleep: Don't wait for SYNC_STATE_ONLY device links Date: Thu, 11 Sep 2025 19:16:03 +0800 Message-ID: <20250911112058.3610201-2-treapking@chromium.org> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog In-Reply-To: <20250911112058.3610201-1-treapking@chromium.org> References: <20250911112058.3610201-1-treapking@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 = "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. Use device_link_flag_is_sync_state_only() 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 v2: - Update commit message - Use device_link_flag_is_sync_state_only() drivers/base/power/main.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) 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) != 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); @@ -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) != 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); -- 2.51.0.384.g4c02a37b29-goog