[U-Boot] [PATCH] arm: mvebu: move i2c slave disable to generic SPL code

[Baruch Siach]

Hi Maxime,

On Tue, May 29, 2018 at 06:32:01PM +0200, Maxime Ripard wrote:
> On Tue, May 29, 2018 at 05:43:30PM +0200, Stefan Roese wrote:
> > > On Mon, May 28, 2018 at 11:04:38AM +0200, Stefan Roese wrote:
> > > I went back to the thread a bit, but I couldn't really understand what
> > > the issue was exactly. Do you have a spurious slave with the
> > > controller at the address 0x64? When would it happen? Anytime you for
> > > example probe the i2c bus?
> > 
> > On the Marvell platforms (Kirkwood, Armada 38x, possibly others), the
> > SoC has the address 0x64 reserved as its I2C slave address (for other
> > masters). So this address is not available for I2C devices attached
> > to the I2C bus. With this patch (via this debug register), this slave
> > address can be "free'ed" making it available for other I2C devices.
> 
> Ok. And that fantom slave can be accessed from the controller itself
> when it's the master, or it's only usable by other masters on the bus?
> 
> ie, an i2cdetect running on that bus from that controller would detect
> the slave you were mentionning? If so, then we don't have it on the
> Allwinner SoCs (or it's not enabled by default at least).

Thanks for testing.

On Armada 38x SoCs this phantom slave only shows up when the bus rate is 
100KHz. At higher rates this slave doesn't show in i2cdetect output, but it 
does interfere with long i2c transfers causing bus lockup.

baruch

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