Re: LTC3651 and other GPIO chargers

[Mike Looijmans <mike.looijmans@topic.nl>]

On 26-06-17 18:21, Ladislav Michl wrote:
> Hi there!
> 
> A driver for LTC3651 was recently added to -next
> https://patchwork.kernel.org/patch/9717049/
> which brings a question whenever we want to add separate driver
> (or vendor specific bindings) for ever growing list of similar
> chargers. For example those using the same status output lines
> are: BQ24232HA, LTC4007, LTM8061, RT9502, LT3651, LT3650, TP4056,
> MAX1737...
> Others for example BQ24032A and LM3658 (which I have to support)
> are using different status encoding, ie. LM3658:
> 
> stat1	stat2		Condition
>    0	  0	Power-Down, charging is suspended or interrupted
>    1	  0	Pre-qualification mode, CC and CV charging
>    0	  1	Charge is completed
>    1	  1	Bad battery (Safety timer expired), or LDO mode
> 
> What about extending gpio-charger instead?
> - allow gpio list fdt subnode
>    - consider each gpio line to represent bit in a word
> - provide per property subnodes
>    - each subnode holds a mask and mapping to property values
> This way we should be able to cover most chargers providing status
> using gpios. Comments welcome and appreciated - those will turn into
> implementation.

It's an interesting idea, and while writing the ltc3651 driver, I was thinking 
along those lines already. However, there are only two gpio charger drivers 
now, so I didn't see the need yet.

The table is an interesting approach. Something else to consider: Some gpio 
chargers allow control as well, e.g. pulling the "charging" ping low 
externally forces the charging to stop.

Something that might help is to create a "GPIO charger" sub-menu in Kconfig, 
to make hunting for these drivers a bit easier.


Kind regards,

Mike Looijmans
System Expert

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