I2C MV64XXX: Showing Allwinner debug LCR register in bus lock case

I2C MV64XXX: Showing Allwinner debug LCR register in bus lock case

[Hermann Lauer]

Dear Maintainers,

if Allwinner i2c locks, the is a LCR register (reg_base + 0x20),
which shows directly the state of the SCL and SDA lines. So you can
see which line (if any) is pulled externally low.

Is there a similar usefull register in the original MV64XXX MARVELL chip?

I'd like to make the patch https://bitbucket.org/hlauer/kernel/src/master/patches/i2c-buslock.patchl working for that chip, too.

Thanks for any ideas.

Greetings
  Hermann

-- 
Administration/Zentrale Dienste, Interdiziplinaeres 
Zentrum fuer wissenschaftliches Rechnen der Universitaet Heidelberg
IWR; INF 205; 69120 Heidelberg; Tel: (06221)54-14405 Fax: -14427
Email: Hermann.Lauer@iwr.uni-heidelberg.de

Re: I2C MV64XXX: Showing Allwinner debug LCR register in bus lock case

[Gregory CLEMENT]

Hello Hermann,

> Dear Maintainers,
>
> if Allwinner i2c locks, the is a LCR register (reg_base + 0x20),
> which shows directly the state of the SCL and SDA lines. So you can
> see which line (if any) is pulled externally low.
>
> Is there a similar usefull register in the original MV64XXX MARVELL
> chip?

I've check on the Armada 38x datasheet and at least on this one there is
no such register or register with similar information. That's mean you
won't be able to use it for any device only the Allwinner ones.

Grégory

>
> I'd like to make the patch https://bitbucket.org/hlauer/kernel/src/master/patches/i2c-buslock.patchl working for that chip, too.
>
> Thanks for any ideas.
>
> Greetings
>   Hermann
>
> -- 
> Administration/Zentrale Dienste, Interdiziplinaeres 
> Zentrum fuer wissenschaftliches Rechnen der Universitaet Heidelberg
> IWR; INF 205; 69120 Heidelberg; Tel: (06221)54-14405 Fax: -14427
> Email: Hermann.Lauer@iwr.uni-heidelberg.de

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com

Re: Re: I2C MV64XXX: Showing Allwinner debug LCR register in bus lock case

[Hermann.Lauer]

Hello Grégory,

On Fri, Jul 30, 2021 at 04:28:58PM +0200, Gregory CLEMENT wrote:
> > if Allwinner i2c locks, the is a LCR register (reg_base + 0x20),
> > which shows directly the state of the SCL and SDA lines. So you can
> > see which line (if any) is pulled externally low.
> >
> > Is there a similar usefull register in the original MV64XXX MARVELL
> > chip?
> 
> I've check on the Armada 38x datasheet and at least on this one there is
> no such register or register with similar information. That's mean you
> won't be able to use it for any device only the Allwinner ones.

Thanks for looking! So, is ifdefing in the driver then the best solution to
display that valueable information?

Thanks for any idea,
 greetings
  Hermann

> > I'd like to make the patch https://bitbucket.org/hlauer/kernel/src/master/patches/i2c-buslock.patchl working for that chip, too.