Hi,
On 23/07/2017 at 22:15:24 +0200, Heiner Kallweit wrote:
> When working on refactoring parts of the ds1307 I stumbled across the fact
> that there are two rtc drivers claiming to support the Epson RX8025 chip.
>
> 1. ds1307 claims to support also this chip. Support was added in 2009,
> however I have doubts that it actually works.
> RX8025 needs a special addressing mode (register address has to be
> left-shifted by 4 bits) which is implemented for both control
> registers but not for the standard registers.
>
> Also support for this chip misses the fix from patch 2e10e74df72
> ("rtc: rx8025: fix transfer mode")
>
> I'm curious whether support for this chip was ever tested, commit message
> of a216685818a5 "rtc: add EPSON RX8025 support to DS1307 RTC driver"
> does not mention that this piece of code was tested with any device
> with this chip.
>
> 2. There's a separate driver for this chip (rtc-rx8025), also added in 2009.
> This drivers is actively maintained.
>
> The separate driver mentions that it supports SA/NB variants of the chip.
> There's no info regarding supported chip variants in the ds1307-integrated
> driver. So there is a small chance that both drivers support different
> chip variants (in this case however the ds1307-integrated driver should
> clearly mention this, also in the Kconfig help text).
>
> For me it's more likely that both drivers try support the same chip.
> Having said that I would propose to remove (rudimentary) RX8025 support
> in ds1307. As a first step we could leave the code in but use a WARN_ON
> to notify potential users that this code is deprecated and they should
> use the separate driver instead.
>
The remaining issue is described here:
https://groups.google.com/d/msg/rtc-linux/M_uv9YkRbC8/MaKpMa3LGgAJ
It is even more apparent after your regmap rework.
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
