This is a note to let you know that I've just added the patch titled
iio: chemical: ccs811: Corrected firmware boot/application mode
to my staging git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git in the staging-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From b91e146c38b003c899710ede6d05fc824675e386 Mon Sep 17 00:00:00 2001
From: Richard Lai richard@richardman.com Date: Sat, 17 Feb 2018 16:28:24 +0000 Subject: iio: chemical: ccs811: Corrected firmware boot/application mode transition
CCS811 has different I2C register maps in boot and application mode. When CCS811 is in boot mode, register APP_START (0xF4) is used to transit the firmware state from boot to application mode. However, APP_START is not a valid register location when CCS811 is in application mode (refer to "CCS811 Bootloader Register Map" and "CCS811 Application Register Map" in CCS811 datasheet). The driver should not attempt to perform a write to APP_START while CCS811 is in application mode, as this is not a valid or documented register location.
When prob function is being called, the driver assumes the CCS811 sensor is in boot mode, and attempts to perform a write to APP_START. Although CCS811 powers-up in boot mode, it may have already been transited to application mode by previous instances, e.g. unload and reload device driver by the system, or explicitly by user. Depending on the system design, CCS811 sensor may be permanently connected to system power source rather than power controlled by GPIO, hence it is possible that the sensor is never power reset, thus the firmware could be in either boot or application mode at any given time when driver prob function is being called.
This patch checks the STATUS register before attempting to send a write to APP_START. Only if the firmware is not in application mode and has valid firmware application loaded, then it will continue to start transiting the firmware boot to application mode.
Signed-off-by: Richard Lai richard@richardman.com Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com --- drivers/iio/chemical/ccs811.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c index fbe2431f5b81..1ea9f5513b02 100644 --- a/drivers/iio/chemical/ccs811.c +++ b/drivers/iio/chemical/ccs811.c @@ -133,6 +133,9 @@ static int ccs811_start_sensor_application(struct i2c_client *client) if (ret < 0) return ret;
+ if ((ret & CCS811_STATUS_FW_MODE_APPLICATION)) + return 0; + if ((ret & CCS811_STATUS_APP_VALID_MASK) != CCS811_STATUS_APP_VALID_LOADED) return -EIO;