On Tue, Dec 2, 2014 at 1:47 AM, Thierry Reding <thierry.reding@xxxxxxxxx> wrote: > On Mon, Nov 24, 2014 at 04:17:17PM -0800, Andrew Bresticker wrote: >> The Tegra xHCI controller's firmware communicates requests to the host >> processor through a mailbox interface. While there is only a single >> physical channel, messages sent by the controller can be divided >> into two groups: those intended for the PHY driver and those intended >> for the host-controller driver. The requesting driver is assigned >> one of two virtual channels when the single physical channel is >> requested. All incoming messages are sent to both virtual channels. >> >> Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx> >> Reviewed-by: Stephen Warren <swarren@xxxxxxxxxx> >> --- >> Thierry, >> >> I've left this as a separate driver because I don't think it should be >> combined with the xHCI host. Stephen and I discussed this earlier in >> review of v1 of this series and he agreed that the mailbox belongs in >> its own DT node and driver. > > My objection wasn't strictly against merging the drivers. What I don't > want to see is two devices sharing the same memory-mapped regions in DT. > > That's based on earlier discussion with Stephen as well, because we have > had the same problem with USB and USB-PHY before. Unless I completely > misinterpreted we came to the conclusion that we should avoid this in > the future. Yes, I understand your objection to having multiple drivers map the same IO memory, however Stephen and I discussed this before [1] and came to the conclusion that, although mapping the MMIO region in both drivers was non-ideal, the alternatives had their own drawbacks as well and that the approach I had taken was fine. > Like I said, this doesn't mean that both need to be in the same driver. > We could use MFD for example, or provide an entry point in the mailbox > driver that can be called from the XUSB driver to instantiate the > mailbox (which is really the same as MFD). This does not look like the typical MFD, but I would agree that it's the only reasonable alternative. If Lee is fine with it, then I suppose I could go the MFD route... Lee: for context, the mailbox registers live in one of the host-controller's MMIO regions - there are no other shared resources. This has been discussed, along with a possible binding, in [1] as well. [1] https://lkml.org/lkml/2014/8/27/727 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
