On Tue, Jun 09, 2015 at 06:29:31PM +0300, Roger Quadros wrote: > 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. > If dr_mode = "peripheral", we should not create OTG descriptor, otherwise, the otg device at other side may consider it is an "otg" device. Peter > > > > > > 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 -- Best Regards, Peter Chen -- 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
