Hi, I'm currently working on Device Tree support for the HSI subsystem to get the Nokia N900 modem working in the mainline kernel. I guess the key question for the binding has been asked by Mark: Mark Rutland <mark.rutland@xxxxxxx> wrote [0]: > Does HSI have an addressing scheme, or does each port > have a single device? It's easy to answer the question in an abstract way: A HSI link connects two processors with each other providing multiple logical channels. The problem is, that only the physical layer is specified AFAIK (I do not have access to HSI specification, so I do not know for sure). Thus the exact usage of the channels is vendor specific. For the Nokia N900 modem the following one of the following bindings seem senseful to me: ========= Variant A ========= hsi-port { /* some nodes describing the port */ n900_modem: client-device { compatible = "nokia,n900-modem"; reg = <0>, <1>, <2>, <3>; reg-names = "mcsaab-control", "speech-control", "mcsaab-data", "speech-data"; hsi-mode = "stream"; hsi-speed-kbps = <55000>; hsi-flow = "synchronized"; hsi-arb-mode = "round-robin"; }; }; ############################# ========= Variant B ========= hsi-port { /* some nodes describing the port */ cmt_mcsaab: client-device@0 { compatible = "nokia,mcsaab-protocol"; reg = <0>, <2>; reg-names = "mcsaab-control", "mcsaab-data"; hsi-mode = "stream"; hsi-channels = <4>; hsi-speed-kbps = <55000>; hsi-flow = "synchronized"; hsi-arb-mode = "round-robin"; }; cmt_speech: client-device@1 { compatible = "nokia,cmt-speech"; reg = <1>, <4>; reg-names = "speech-control", "speech-data"; hsi-mode = "stream"; hsi-channels = <4>; hsi-speed-kbps = <55000>; hsi-flow = "synchronized"; hsi-arb-mode = "round-robin"; }; }; ############################# Both bindings are simplified and do not map all of the hardware's capabilities: Some settings can be configured differently for RX and TX. It should be easy to extend the support for e.g. hsi-mode-rx and hsi-mode-tx once this is needed. For devices configuring them the same having just one node seems better to me (I assume almost all devices want them to be the same). As far as I can see only ST-Erricson has also HSI clients prepared for the mainline kernel. It would be nice to get some feedback from you. If you know more HSI users, which are not yet Cc'd please feel free to point them here. [0] http://article.gmane.org/gmane.linux.kernel/1654456 -- Sebastian
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