From cd998ded5c1295c690285c04a6ef8bc014d14234 Mon Sep 17 00:00:00 2001 From: Jarkko Nikula Date: Thu, 11 Feb 2016 16:36:03 +0200 Subject: [PATCH] i2c: designware: Prevent runtime suspend during adapter registration There can be unnecessary runtime suspend-resume cycle during i2c-designware-platdrv probe when it registers the I2C adapter device. This happens because i2c-designware-platdrv is set to initially active platform device in its probe function and is a parent of I2C adapter. In that case power.usage_count of i2c-designware device is zero and pm_runtime_get()/pm_runtime_put() cycle during probe could put it into runtime suspend. This happens when the i2c_register_adapter() calls the device_register(): i2c_register_adapter device_register device_add bus_probe_device device_initial_probe __device_attach if (dev->parent) pm_runtime_get_sync(dev->parent) ... if (dev->parent) pm_runtime_put(dev->parent) After that the i2c_register_adapter() continues registering I2C slave devices. In case slave device probe does I2C transfers the parent will resume again and thus get a needless runtime suspend/resume cycle during adapter registration. Prevent this while retaining the runtime PM status of i2c-designware by only incrementing/decrementing device power usage count during I2C adapter registration. That makes sure there won't be spurious runtime PM status changes and lets the driver core to idle the device after probe finishes. Signed-off-by: Jarkko Nikula Acked-by: Mika Westerberg Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-designware-core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c index 4255eaab96d1..99b54be6ba73 100644 --- a/drivers/i2c/busses/i2c-designware-core.c +++ b/drivers/i2c/busses/i2c-designware-core.c @@ -881,9 +881,17 @@ int i2c_dw_probe(struct dw_i2c_dev *dev) return r; } + /* + * Increment PM usage count during adapter registration in order to + * avoid possible spurious runtime suspend when adapter device is + * registered to the device core and immediate resume in case bus has + * registered I2C slaves that do I2C transfers in their probe. + */ + pm_runtime_get_noresume(dev->dev); r = i2c_add_numbered_adapter(adap); if (r) dev_err(dev->dev, "failure adding adapter: %d\n", r); + pm_runtime_put_noidle(dev->dev); return r; } -- 2.34.1