Linux kernel
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Brian Norris
authored
This driver was originally submitted for the TI BQ20Z75 battery IC (commit a7640bfa ("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 17c6d397 ("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 17c6d397 ("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>
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