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Brian Norris 76b16f4cdf power: supply: sbs-battery: don't assume MANUFACTURER_DATA formats 
This driver was originally submitted for the TI BQ20Z75 battery IC
(commit a7640bfa10 ("power_supply: Add driver for TI BQ20Z75 gas gauge
IC")) and later renamed to express generic SBS support. While it's
mostly true that this driver implemented a standard SBS command set, it
takes liberties with the REG_MANUFACTURER_DATA register. This register
is specified in the SBS spec, but it doesn't make any mention of what
its actual contents are.

We've sort of noticed this optionality previously, with commit
17c6d3979e ("sbs-battery: make writes to ManufacturerAccess
optional"), where we found that some batteries NAK writes to this
register.

What this really means is that so far, we've just been lucky that most
batteries have either been compatible with the TI chip, or else at least
haven't reported highly-unexpected values.

For instance, one battery I have here seems to report either 0x0000 or
0x0100 to the MANUFACTURER_ACCESS_STATUS command -- while this seems to
match either Wake Up (bits[11:8] = 0000b) or Normal Discharge
(bits[11:8] = 0001b) status for the TI part [1], they don't seem to
actually correspond to real states (for instance, I never see 0101b =
Charge, even when charging).

On other batteries, I'm getting apparently random data in return, which
means that occasionally, we interpret this as "battery not present" or
"battery is not healthy".

All in all, it seems to be a really bad idea to make assumptions about
REG_MANUFACTURER_DATA, unless we already know what battery we're using.
Therefore, this patch reimplements the "present" and "health" checks to
the following on most SBS batteries:

1. HEALTH: report "unknown" -- I couldn't find a standard SBS command
   that gives us much useful here
2. PRESENT: just send a REG_STATUS command; if it succeeds, then the
   battery is present

Also, we stop sending MANUFACTURER_ACCESS_SLEEP to non-TI parts. I have
no proof that this is useful and supported.

If someone explicitly provided a 'ti,bq20z75' compatible property, then
we continue to use the existing TI command behaviors, and we effectively
revert commit 17c6d3979e ("sbs-battery: make writes to
ManufacturerAccess optional") to again make these commands required.

[1] http://www.ti.com/lit/er/sluu265a/sluu265a.pdf

Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
2018-06-28 14:09:46 +02:00
arch Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
block for-linus-20180616 2018-06-17 05:37:55 +09:00
certs docs: Fix some broken references 2018-06-15 18:10:01 -03:00
crypto docs: Fix some broken references 2018-06-15 18:10:01 -03:00
Documentation for-linus-20180616 2018-06-17 05:37:55 +09:00
drivers power: supply: sbs-battery: don't assume MANUFACTURER_DATA formats 2018-06-28 14:09:46 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
include for-linus-20180616 2018-06-17 05:37:55 +09:00
init Kbuild updates for v4.18 (2nd) 2018-06-13 08:40:34 -07:00
ipc ipc: use new return type vm_fault_t 2018-06-15 07:55:25 +09:00
kernel Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
lib docs: Fix some broken references 2018-06-15 18:10:01 -03:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
mm mm: fix oom_kill event handling 2018-06-15 07:55:25 +09:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-06-16 07:39:34 +09:00
samples VFIO updates for v4.18 2018-06-12 13:11:26 -07:00
scripts scripts/documentation-file-ref-check: check tools/*/Documentation 2018-06-15 18:10:01 -03:00
security docs: Fix some broken references 2018-06-15 18:10:01 -03:00
sound docs: Fix some broken references 2018-06-15 18:10:01 -03:00
tools Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge branch 'asoc-4.17' into asoc-4.18 for compress dependencies 2018-04-26 12:24:28 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: add basic helper macros to scripts/Kconfig.include 2018-05-29 03:31:19 +09:00
MAINTAINERS Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
Makefile Linux 4.18-rc1 2018-06-17 08:04:49 +09:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.