From e866853d67868ac0f7e0779d19aaad07285c9ff3 Mon Sep 17 00:00:00 2001 From: Martin Kepplinger Date: Thu, 3 Mar 2016 09:24:02 +0100 Subject: [PATCH] iio: mma8452: avoid switching to active because of config change The devices' config registers can only be changed in standby mode. Up until now the driver just held the device *always* active, so for changing a config it was *always* necessary to switch to standby. For upcoming support for runtime pm, the device can as well be in standby mode. Instead of putting runtime pm functions in there, just keep the device in standby if it already is. This section is protected by a lock after all. Signed-off-by: Martin Kepplinger Signed-off-by: Christoph Muellner Signed-off-by: Jonathan Cameron --- drivers/iio/accel/mma8452.c | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c index 17d72bc..9c4a84a 100644 --- a/drivers/iio/accel/mma8452.c +++ b/drivers/iio/accel/mma8452.c @@ -393,24 +393,47 @@ static int mma8452_active(struct mma8452_data *data) data->ctrl_reg1); } +/* returns >0 if active, 0 if in standby and <0 on error */ +static int mma8452_is_active(struct mma8452_data *data) +{ + int reg; + + reg = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG1); + if (reg < 0) + return reg; + + return reg & MMA8452_CTRL_ACTIVE; +} + static int mma8452_change_config(struct mma8452_data *data, u8 reg, u8 val) { int ret; + int is_active; mutex_lock(&data->lock); - /* config can only be changed when in standby */ - ret = mma8452_standby(data); - if (ret < 0) + is_active = mma8452_is_active(data); + if (is_active < 0) { + ret = is_active; goto fail; + } + + /* config can only be changed when in standby */ + if (is_active > 0) { + ret = mma8452_standby(data); + if (ret < 0) + goto fail; + } ret = i2c_smbus_write_byte_data(data->client, reg, val); if (ret < 0) goto fail; - ret = mma8452_active(data); - if (ret < 0) - goto fail; + if (is_active > 0) { + ret = mma8452_active(data); + if (ret < 0) + goto fail; + } ret = 0; fail: -- 2.7.4