On Mon, 26 Feb 2018 21:36:07 +0100 Boris Brezillon <boris.brezil...@bootlin.com> wrote:
> > >>> + > > >>> +/** > > >>> + * struct i3c_master_controller_ops - I3C master methods > > >>> + * @bus_init: hook responsible for the I3C bus initialization. This > > >>> + * initialization should follow the steps described in the > > >>> I3C > > >>> + * specification. This hook is called with the bus lock held > > >>> in > > >>> + * write mode, which means all _locked() helpers can safely > > >>> be > > >>> + * called from there > > >>> + * @bus_cleanup: cleanup everything done in > > >>> + * &i3c_master_controller_ops->bus_init(). This function > > >>> is > > >>> + * optional and should only be implemented if > > >>> + * &i3c_master_controller_ops->bus_init() attached > > >>> private data > > >>> + * to I3C/I2C devices. This hook is called with the bus > > >>> lock > > >>> + * held in write mode, which means all _locked() helpers > > >>> can > > >>> + * safely be called from there > > >>> + * @supports_ccc_cmd: should return true if the CCC command is > > >>> supported, false > > >>> + * otherwise > > >>> + * @send_ccc_cmd: send a CCC command > > >>> + * @send_hdr_cmds: send one or several HDR commands. If there is more > > >>> than one > > >>> + * command, they should ideally be sent in the same HDR > > >>> + * transaction > > >>> + * @priv_xfers: do one or several private I3C SDR transfers > > >>> + * @i2c_xfers: do one or several I2C transfers > > >>> + * @request_ibi: attach an IBI handler to an I3C device. This implies > > >>> defining > > >>> + * an IBI handler and the constraints of the IBI (maximum > > >>> payload > > >>> + * length and number of pre-allocated slots). > > >>> + * Some controllers support less IBI-capable devices than > > >>> regular > > >>> + * devices, so this method might return -%EBUSY if > > >>> there's no > > >>> + * more space for an extra IBI registration > > >>> + * @free_ibi: free an IBI previously requested with ->request_ibi(). > > >>> The IBI > > >>> + * should have been disabled with ->disable_irq() prior to > > >>> that > > >>> + * @enable_ibi: enable the IBI. Only valid if ->request_ibi() has been > > >>> called > > >>> + * prior to ->enable_ibi(). The controller should first > > >>> enable > > >>> + * the IBI on the controller end (for example, unmask the > > >>> hardware > > >>> + * IRQ) and then send the ENEC CCC command (with the IBI > > >>> flag set) > > >>> + * to the I3C device > > >>> + * @disable_ibi: disable an IBI. First send the DISEC CCC command with > > >>> the IBI > > >>> + * flag set and then deactivate the hardware IRQ on the > > >>> + * controller end > > >>> + * @recycle_ibi_slot: recycle an IBI slot. Called every time an IBI > > >>> has been > > >>> + * processed by its handler. The IBI slot should be > > >>> put back > > >>> + * in the IBI slot pool so that the controller can > > >>> re-use it > > >>> + * for a future IBI > > >>> + * > > >>> + * One of the most important hooks in these ops is > > >>> + * &i3c_master_controller_ops->bus_init(). Here is a non-exhaustive > > >>> list of > > >>> + * things that should be done in > > >>> &i3c_master_controller_ops->bus_init(): > > >>> + * > > >>> + * 1) call i3c_master_set_info() with all information describing the > > >>> master > > >>> + * 2) ask all slaves to drop their dynamic address by sending the > > >>> RSTDAA CCC > > >>> + * with i3c_master_rstdaa_locked() > > >>> + * 3) ask all slaves to disable IBIs using i3c_master_disec_locked() > > >>> + * 4) start a DDA procedure by sending the ENTDAA CCC with > > >>> + * i3c_master_entdaa_locked(), or using the internal DAA logic > > >>> provided by > > >>> + * your controller > > >> You mean SETDASA CCC command? > > > No, I really mean ENTDAA and DAA. By internal DAA logic I mean that > > > some controllers are probably automating the whole DAA procedure, while > > > others may let the SW control every step. > > My understanding is that i3c_master_entdaa_locked() will trigger the DAA > > process > > and DAA can be done by SETDASA, ENTDAA and later after the bus > > initialization > > with SETNEWDA. > > No. Only ENTDAA can trigger a DAA procedure. SETDASA is here to assign > a single dynamic address to a device that already has a static address > but no dynamic address yet, and SETNEWDA is here to modify the dynamic > address of a device that already has one. > > > > > I think the DAA process should be more generic, right now is only made > > through > > the ENTDAA command with (cmd.ndests = 1). > > I mean, shouldn't this be made by the core? First doing DAA for the devices > > declared and them try do discover the rest of devices on the bus. > > Can you detail a bit more? If the only part you're complaining about is > pre-assignment of dynamic addresses with SETDASA when a device is > declared in the DT with a reg and dynamic-address property, then yes, I > think I can provide an helper for that. But this helper would still have > to be called from the master controller driver (from ->bus_init() or > after a Hot-Join). > > Now, if the question is, is there a way we can automate things even more > and completely implement DAA from the core? I doubt it, because the way > the core will trigger DAA, expose discovered devices or allow you to > declare manually assigned addresses is likely to be > controller-dependent. > When I designed the framework I took the decision to base my work on the > spec rather than focusing on the I3C master controller I had to support > (Cadence). This is the reason I decided to keep the interface as simple > as possible at the risk of encouraging code-duplication (at first) > rather than coming up with an interface that is designed with a single > controller in mind and having to break things every time a new > controller comes out. > > Thank you for you comments, but I'd like to know if some of my design > choices are blocking you to support your controller. What I've seen so > far is a collection of things that might be relevant to fix (though > most of them are subject to interpretation and/or a matter of taste), > but nothing that should really block you. Well, that's not entirely true: I agree that something is missing in ->priv_xfers() to let the controller know about the device limitations, and this could be a blocking aspect. -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
