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Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Ulf Hansson Subject: [PATCH v2] PM: runtime: Return properly from rpm_resume() if dev->power.needs_force_resume flag is set Date: Fri, 23 Sep 2022 20:49:04 +0800 Message-Id: <20220923124904.1373936-1-victor.liu@nxp.com> X-Mailer: git-send-email 2.37.1 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SG2PR06CA0234.apcprd06.prod.outlook.com (2603:1096:4:ac::18) To AM7PR04MB7046.eurprd04.prod.outlook.com (2603:10a6:20b:113::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AM7PR04MB7046:EE_|PA4PR04MB9461:EE_ X-MS-Office365-Filtering-Correlation-Id: a32ab6bf-4c39-430a-d50b-08da9d61cbc0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:AM7PR04MB7046.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(4636009)(396003)(136003)(346002)(376002)(366004)(39860400002)(451199015)(1076003)(2616005)(186003)(2906002)(5660300002)(36756003)(38350700002)(38100700002)(86362001)(83380400001)(54906003)(6916009)(316002)(6512007)(6486002)(478600001)(6666004)(41300700001)(66946007)(52116002)(66476007)(8676002)(66556008)(26005)(4326008)(8936002)(6506007);DIR:OUT;SFP:1101; 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charset="utf-8" After a device transitions to sleep state through it's system suspend callback pm_runtime_force_suspend(), the device's driver may still try to do runtime PM for the device(runtime suspend first and then runtime resume) although runtime PM is disabled by that callback. The runtime PM operations would not touch the device effectively and the device is assumed to be resumed through it's system resume callback pm_runtime_force_resume(). The problem is that since the device's runtime PM status is RPM_SUSPENDED in the sleep state, rpm_resume() would not take the device as in already active status and would return -EACCES instead of 1. The error code -EACCES may make the device's driver put the device into runtime suspend status with the RPM_GET_PUT flag set and hence drop the device's usage count to 1. Then, at dpm_complete stage, device_complete() would call pm_runtime_put() to drop the device's usage count again to 0 and call rpm_idle() to try to put the device into runtime PM suspend status. So, the device could eventually stay at the runtime PM suspend status. A real problematic case is the panel-simple.c driver(works with a downstream DRM device driver), where the optional enable_gpio(controlled by the runtime PM callbacks) will be disabled through pm_runtime_put() called in device_complete() if a DRM atomic commit(triggered by a DRM device's system resume callback) tries to do runtime PM resume for the panel before the panel is active with force resume: 1) System suspend: - pm_runtime_force_suspend() - panel_simple_suspend() // enable_gpio is disabled 2) Runtime suspend with a DRM atomic commit: - panel_simple_unprepare() - pm_runtime_put_autosuspend() // drop device usage count to 1 3) Runtime resume with a DRM atomic commit: - panel_simple_prepare() - pm_runtime_get_sync() // increase device usage count to 2 - rpm_resume() // return -EACCES - pm_runtime_put_autosuspend() // drop device usage count to 1 4) System resume: - pm_runtime_force_resume() - panel_simple_resume() // enable_gpio is enabled 5) PM transition complete: - dpm_complete() - device_complete() - pm_runtime_put() // drop device usage count to 0 - rpm_idle() - rpm_suspend() // start hrtimer with expires 6) hrtimer expires: - pm_suspend_timer_fn() - rpm_suspend() // queue work on pm_wq 7) work function is called: - pm_runtime_work() - rpm_suspend() - panel_simple_suspend() // enable_gpio is disabled Fix the issue by checking dev->power.needs_force_resume flag in rpm_resume() so that it returns 1 instead of -EACCES in this scenario, since the flag is set in pm_runtime_force_suspend(). Then, device usage count will be 1 after pm_runtime_put() is called at dpm_complete stage. Also, update the documentation to change the description of pm_runtime_resume() to reflect the new behavior of rpm_resume(). Cc: Rafael J. Wysocki Cc: Len Brown Cc: Pavel Machek Cc: Greg Kroah-Hartman Cc: Ulf Hansson Signed-off-by: Liu Ying --- v1->v2: * Fix commit message to tell the reason why the issue happens, that is, zeroed device usage count in pm_runtime_put() at dpm_complete stage eventually makes the device be in runtime PM suspend status. Documentation/power/runtime_pm.rst | 14 +++++++------- drivers/base/power/runtime.c | 2 ++ 2 files changed, 9 insertions(+), 7 deletions(-) diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runti= me_pm.rst index 65b86e487afe..6266f0ac02a8 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -337,13 +337,13 @@ drivers/base/power/runtime.c and include/linux/pm_run= time.h: =20 `int pm_runtime_resume(struct device *dev);` - execute the subsystem-level resume callback for the device; returns = 0 on - success, 1 if the device's runtime PM status is already 'active' (al= so if - 'power.disable_depth' is nonzero, but the status was 'active' when i= t was - changing from 0 to 1) or error code on failure, where -EAGAIN means = it may - be safe to attempt to resume the device again in future, but - 'power.runtime_error' should be checked additionally, and -EACCES me= ans - that the callback could not be run, because 'power.disable_depth' was - different from 0 + success, 1 if the device's runtime PM status is assumed to be 'activ= e' + with force resume or is already 'active' (also if 'power.disable_dep= th' is + nonzero, but the status was 'active' when it was changing from 0 to = 1) or + error code on failure, where -EAGAIN means it may be safe to attempt= to + resume the device again in future, but 'power.runtime_error' should = be + checked additionally, and -EACCES means that the callback could not = be + run, because 'power.disable_depth' was different from 0 =20 `int pm_runtime_resume_and_get(struct device *dev);` - run pm_runtime_resume(dev) and if successful, increment the device's diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 997be3ac20a7..0bce66ea0036 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -762,6 +762,8 @@ static int rpm_resume(struct device *dev, int rpmflags) repeat: if (dev->power.runtime_error) { retval =3D -EINVAL; + } else if (dev->power.needs_force_resume) { + retval =3D 1; } else if (dev->power.disable_depth > 0) { if (dev->power.runtime_status =3D=3D RPM_ACTIVE && dev->power.last_status =3D=3D RPM_ACTIVE) --=20 2.37.1