Hi, On Thu, Jan 22, 2015 at 11:43:30AM +0100, Maxime Ripard wrote: > Hi Yegor, > > On Thu, Jan 22, 2015 at 08:37:45AM +0100, Yegor Yefremov wrote: > > On 21.01.2015 19:53, Bin Liu wrote: > > > Hi, > > > > > > On Wed, Jan 21, 2015 at 10:06 AM, Maxime Ripard > > > <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > > >> Hi Felipe, > > >> > > >> I'm currently working on a custom AM335x-based board, that has a OTG > > >> connector wired to one of the musb controlers, and Linux 3.17 > > >> > > >> This OTG connector seems to behave in a weird way when it comes to > > >> switching from one role to another: > > >> > > >> - The host mode works with CONFIG_USB_MUSB_DUAL_ROLE set, only if > > >> the dr_mode is set to host in the DT, and only if we plug the USB > > >> device after the kernel has booted. Otherwise, even though the > > >> controller seems to be set up as host in the kernel logs, it > > >> doesn't work. When DR-mode is set to otg, DRVVBUS is not high > > >> which surely doesn't help, but there might be some other issues. > > >> > > >> - The gadget mode works with CONFIG_USB_MUSB_DUAL_ROLE, if dr_mode > > >> is set to otg and not host (obviously), and only if we plug the > > >> USB cable after the kernel has booted. > > >> > > >> - The gadget mode works with CONFIG_USB_MUSB_GADGET, and with > > >> dr_mode set to otg, even if we cold plug the device. > > >> > > >> - As you might expect from the two first items, the runtime > > >> switching from gadget to host when CONFIG_USB_MUSB_DUAL_ROLE is > > >> set and dr_mode is set in otg doesn't work either. > > >> > > >> It looks like it's only waiting for an interrupt to occur to read the > > >> ID pin state, without reading its initial value, which would explain > > >> why both the host and gadget enumerate only when a device/cable is > > >> hotplugged, and that there's some configuration bits that differ > > >> whenever dr_mode changes, but I couldn't really see anything standing > > >> out in the driver nor the datasheet. > > >> > > >> Have you already experienced something alike with that driver? > > > > > > I don't use vanilla mainline kernel very often, but I don't have such > > > hotplug issues with TI 3.12/14 kernels [1]. I only use > > > CONFIG_USB_MUSB_DUAL_ROLE though. > > > > > > [1] git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git, branch > > > remote/origin/linux-3.14.y > > > > I have the same experience with 3.15. The switching is working when > > CONFIG_USB_MUSB_DUAL_ROLE is set and dr_mode = "otg". But since 3.16 > > it seems to be broken. Still had no time to bisect this. > > I just gave 3.15 a quick try, and it looks like it can now detect when > the device is acting as a gadget, but the host mode is not working at > all. > > That's a good lead though, I'll dig more into the older versions and > see if some are working better than others. This issue may be related to the fact that the musb controller does not have an ID pin interrupt. Last year I sent a RFC for a soft detection in OTG mode. It has a poll loop which toggles the SESSION bit of the controller to detect devices as host and drops back to device otherwise. This is far away from a good solution. http://lists.infradead.org/pipermail/linux-arm-kernel/2013-October/204519.html Best Regards, Markus -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
Attachment:
signature.asc
Description: Digital signature
