Hi On Mon, 10 Oct 2011, Felipe Balbi wrote: > On Mon, Oct 10, 2011 at 02:22:23PM +0530, Munegowda, Keshava wrote: > > > Here is the highlights of the change in the design of USB Host which > > we can do after kernel 3.2 release; > > > > 1. separate the TLL changes from UHH > > 2. The TLL is be a new platform driver in ./drivers/mfd > > 3. the TLL platform driver will export apis for enable/disable clocks > > and settings. > > TLL should control its clocks through pm_runtime APIs like anything > else. If you really must export APIs to be used by UHH, you need to have > an API so that you can claim/release a TLL channel and get/put for > increasing/decreasing PM counters. > > I still think though, you should try to avoid exporting OMAP-specific > APIs all over the place. Ideally, we would be able to have some way of > saying that UHH and TLL are closely related... something like having the > ability to say e.g. two devices are sibblings of each other, so that we > could ask for a sibbling to wakeup/sleep depending if we need it or not. > > Dunno, maybe I'm drifting here, but I don't think exposing OMAP-specific > APIs is wise. I'm not an USBHOST expert, but I don't think any special sibling relationships or OMAP subarchitecture-specific APIs are needed. The OMAP EHCI/OHCI drivers just need to call a couple of functions in the OMAP TLL driver. Linux already handles function call dependencies between loadable modules transparently (see "man 8 depmod" and EXPORT_SYMBOL). Looks to me like the TLL IP block is only needed for OHCI and some EHCI port modes[1]. The TLL doesn't seem to need much care and feeding. Currently it's programmed during init[2] and then you just enable it when the port is in use[3] and disable it when it is no longer in use[4]. Looks to me like the TLL init function could be rolled into the enable function. So then you'd just create a TLL driver with something like these two symbols exported: omap_usbhost_tll_enable_port(); omap_usbhost_tll_disable_port(); The first function would be called from drivers/usb/host/ehci-omap.c or drivers/usb/host/ohci-omap3.c during omap_usbhs_enable(). It would take the TLL configuration for that port and would reserve it while it is in use. It would call pm_runtime_get_sync() to ensure its clocks were on, etc. The second function would be called from drivers/usb/host/ehci-omap.c or drivers/usb/host/ohci-omap3.c during omap_usbhs_disable(). It would release an already in-use TLL port and would call pm_runtime_put_sync() to allow its clocks to be cut, etc. So it doesn't seem like any extraordinary Linux support is needed to handle this cleanly. But maybe I'm missing something? - Paul All references are as of Linux v3.1-rc9. 1. drivers/mfd/omap-usb-host.c:887, http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/mfd/omap-usb-host.c;h=86e14583a08276fd7f76dddd3afe3433f1dfa9a8;hb=976d167615b64e14bc1491ca51d424e2ba9a5e84#l887 2. drivers/mfd/omap-usb-host.c:894, http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/mfd/omap-usb-host.c;h=86e14583a08276fd7f76dddd3afe3433f1dfa9a8;hb=976d167615b64e14bc1491ca51d424e2ba9a5e84#l894 3. drivers/mfd/omap-usb-host.c:845, http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/mfd/omap-usb-host.c;h=86e14583a08276fd7f76dddd3afe3433f1dfa9a8;hb=976d167615b64e14bc1491ca51d424e2ba9a5e84#l845 4. drivers/mfd/omap-usb-host.c:999, http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/mfd/omap-usb-host.c;h=86e14583a08276fd7f76dddd3afe3433f1dfa9a8;hb=976d167615b64e14bc1491ca51d424e2ba9a5e84#l999 -- 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
