patch "iio: chemical: ccs811: Corrected firmware boot/application mode" added to staging-linus

patch "iio: chemical: ccs811: Corrected firmware boot/application mode" added to staging-linus

[gregkh]

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;
-- 
2.16.2