On Sun, Apr 06, 2014 at 05:37:29PM +0200, Wolfram Sang wrote: > 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. I'd agree with that. Other clients/adapters might need only one of these. Note that you'd probably need a I2C_M_DELAYED_ACK or something. > > > 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? None that we're aware of. Since the PMIC is already most likely initialised, I think we can just use it as if it was already in P2WI mode. > > > 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? Let me see what I can do. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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