On Sun, Apr 06, 2014 at 04:01:52PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 04/04/2014 02:26 PM, Wolfram Sang wrote:
> > 
> >> So what we really have is a single slave i2c host sort of. At least
> >> we could model it like that. The host could be told which address to
> >> listen to (and which single i2c write to do to init the pmic) through
> >> devicetree and then all the differences would be hidden in the host
> >> driver, ie we would check the slave-address and if it is not the single
> >> one we support, we just return the appropriate error for a device not
> >> acking, and everything should work as a regular i2c host which
> >> only supports i2c_smbus_read_byte and i2c_smbus_write_byte.
> > 
> > I'd think we need a new message flag like I2C_M_PUSHPULL which says that
> > this message has only the direction bit instead of the address and needs
> > a parity bit afterwards. In addition to that, we need a new
> > functionality flag I2C_FUNC_PUSHPULL which means the host driver can
> > handle those messages. So, the PMIC driver could query support for
> > I2C_FUNC_SMBUS_BYTE | I2C_FUNC_PUSHPULL and if successful send messages
> > using smbus functions with the new flag set.
> 
> Thanks for the input this sounds good, I guess we'll give this a shot
> when we get around to coding up support for the p2wi block in the A31.

On a second thought, maybe more granularity is better. Like using
I2C_M_DROP_ADDRESS and I2C_M_ADD_PARITY and then make
I2C_CLIENT_PUSHPULL involve I2C_M_DROP_ADDRESS | I2C_M_ADD_PARITY.

> > Not sure about the I2C-to-PushPull switch: Is it 100% host configuration
> > or does it also depend on the one slave attached? 
> 
> The datasheet we've suggests that it actually influences the one slave
> attached. Note that u-boot on this machines will likely already have made
> the switch, but I guess we don't want to count on that.

Can we detect if this switching was already made?

> > Are there some datasheets available?
> 
> The AXP221 is documented here:
> http://linux-sunxi.org/AXP221
> This is translated by one of our community members from a Chinese datasheet.
> 
> The P2WI interface is (somewhat) documented in the A31 datasheet, but we cannot
> share that in public.

Any chance for me to get it if I sign something?

Regards,

   Wolfram