Rob, On Tue, 9 Jun 2015 08:26:20 -0500 Rob Herring <robherring2@xxxxxxxxx> wrote: > On Mon, Jun 8, 2015 at 8:18 PM, Li Jun <b47624@xxxxxxxxxxxxx> wrote: > > On Mon, Jun 08, 2015 at 11:06:49AM -0500, Rob Herring wrote: > >> On Mon, Jun 8, 2015 at 10:02 AM, Li Jun <jun.li@xxxxxxxxxxxxx> wrote: > >> > Add otg version, srp, hnp and adp support for usb OTG port, then those OTG > >> > features don't have to be decided by usb gadget drivers. > >> > > >> > Signed-off-by: Li Jun <jun.li@xxxxxxxxxxxxx> > >> > --- > >> > Documentation/devicetree/bindings/usb/generic.txt | 10 ++++++++++ > >> > 1 file changed, 10 insertions(+) > >> > > >> > diff --git a/Documentation/devicetree/bindings/usb/generic.txt b/Documentation/devicetree/bindings/usb/generic.txt > >> > index 477d5bb..7386f4a 100644 > >> > --- a/Documentation/devicetree/bindings/usb/generic.txt > >> > +++ b/Documentation/devicetree/bindings/usb/generic.txt > >> > @@ -11,6 +11,12 @@ Optional properties: > >> > "peripheral" and "otg". In case this attribute isn't > >> > passed via DT, USB DRD controllers should default to > >> > OTG. > >> > + - otg-rev: tells usb driver the release number of the OTG and EH supplement > >> > + with which the device and its descriptors are compliant, > >> > + in binary-coded decimal (i.e. 2.0 is 0200H). > >> > >> I would assume OTG 2.0 is somehow backwards compatible? Is this a h/w > >> dependency or a driver feature? > >> > > Not fully compatible, OTG 2.0 extend the usb_otg_descriptor by adding a new > > member bcdOTG to identify the OTG version, this descriptor needs to be sent > > to OTG host with correct size and content, so we have to know which release > > version the OTG device is compliant with, either by menuconfig config or pass > > via DT. > > So you have to change the version depending on the host you are > connected to? That really seems strange that plugging in a OTG 2.0 > device to an OTG 1.3 host would not work and doesn't make for a good > user experience. No. The OTG version in the OTG descriptor for any device is usually fixed for the lifetime of the product. Let's assume it is 2.0. If you plug this to OTG 1.0 host, it won't be an issue as OTG 1.0 host doesn't read the BCD version. > > >> > + - srp-support: tells OTG controllers we want to enable SRP. > >> > + - hnp-support: tells OTG controllers we want to enable HNP. > >> > + - adp-support: tells OTG controllers we want to enable ADP. > >> > >> I've recently run into a problem[1] and found that I have to disable > >> OTG in the kernel to get my device to work. Having to turn-off OTG > >> seems like the wrong solution, and shifting the problem to DT seems > >> wrong too. Why is this not a user configurable option (within whatever > >> h/w constraints there are)? > > The problem of below link, seems your device is claiming it's a HNP capable > > OTG device, but connecting to a non-OTG port of your Host, assume your Host > > does have a OTG port, your Host issue a A_ALT_HNP_SUPPORT request to your > > OTG device to remind it can use another port with HNP, but the request failed > > (maybe STALL by your device, this request is defined in OTG 1.3 but obsolete > > in OTG 2.0), so your Host just stopped enumeration of your device, this is not > > reasonable because current OTG code is some out of data. > > Do PCs have OTG ports typically? My expectation is that if I plug in > an OTG device as a B device to any host port, that it will work as a > device no matter what the host OTG capabilities are. If I have to > change the kernel config or DT, that is a problem. AFAIK PCs don't have OTG ports. If you plug in OTG device to a non-otg host port it will work as normal B-device. The host doesn't request for OTG descriptors and doesn't care what OTG features it supports or not. > > > I am trying to make those OTG feaures to be configurable options, you mean > > by sys? > > Yes. why do you need OTG features to be sysfs configurable other than for debugging? > > >> What are the valid combinations? When do we want these enabled or not? > >> Wouldn't default enabled be better? > > > > We want to enable all those support in kernel driver, but some platform or > > hardware may not want to enable any or some of them, so those hardware > > can disable it by not pass the property in dt, the 3 sub features of OTG are > > not mandatory for so called OTG device, normally we at least enable HNP, and > > SRP and ADP are optional. > > Please answer my questions in the doc. > > >> > >> We already have dr_mode property. How is it related to these? dr_mode states what mode the controller will operate in. for dr_mode == "host" we don't care about these otg flags. for dr_mode == "peripheral" or dr_mode == "otg" we care about these OTG flags to create our OTG descriptor on the fly. > > > > dr_mode is to tell the device it will work at OTG mode(there is another simple > > dual role mode which is commom used but not HNP), srp/hnp/adp can further specify > > which protocol the OTG device will support. > > By simple DR, you mean ID pin detect, right. So please define how you > support just ID pin detect vs. other levels of capability. Does only > dr_mode = otg mean ID pin detect? That may be a problem for existing > DTs if you disable other OTG functions because they have not been > added to the DT, then that is a problem. > > I'm feeling less convinced that this belongs in DT at all. Please > convince me otherwise. Yes not specifying anything in DT should work and default to the best OTG version and features supported by the OTG controller. But if the device manufacturer wants to restrict the OTG version to something less or disable some OTG features then the DT flags come into play. cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
