On Thu, Jun 30, 2016 at 10:46:16AM +0530, Lokesh Vutla wrote: > +Dave, Tony, Keerthy, > > Hi Stefan, > > On Tuesday 28 June 2016 09:26 PM, Stefan Eichenberger wrote: > > If a module is not available, omap_hwmod will still try to access the > > registers if it is present in the hwmod_list. If the module is not > > powered at all (e.g. rtc) then linux can't start. It is possible > > to disable the module by setting the state to disabled and to assign > > ti,hwmods an empty string but this leads to the following warning: > > [ 0.188255] omap_hwmod: rtc missing dt data > > [ 0.188273] omap_hwmod: rtc: no MPU register target found > > [ 0.188287] omap_hwmod: rtc: no dt node > > [ 0.188300] ------------[ cut here ]------------ > > [ 0.188330] WARNING: CPU: 0 PID: 1 at arch/arm/mach-omap2/omap_hwmod.c:2493 _init+0x1fc/0x45c() > > [ 0.188344] omap_hwmod: rtc: doesn't have mpu register target base > > [ 0.188357] Modules linked in: > > [ 0.188388] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-00004-g17704c9-dirty #24 > > [ 0.188402] Hardware name: Generic AM33XX (Flattened Device Tree) > > [ 0.188445] [<c0017c24>] (unwind_backtrace) from [<c0013f88>] (show_stack+0x10/0x14) > > [ 0.188474] [<c0013f88>] (show_stack) from [<c0347860>] (dump_stack+0x84/0x9c) > > [ 0.188508] [<c0347860>] (dump_stack) from [<c003ca40>] (warn_slowpath_common+0x78/0xb4) > > [ 0.188534] [<c003ca40>] (warn_slowpath_common) from [<c003caac>] (warn_slowpath_fmt+0x30/0x40) > > [ 0.188558] [<c003caac>] (warn_slowpath_fmt) from [<c08b76e0>] (_init+0x1fc/0x45c) > > [ 0.188589] [<c08b76e0>] (_init) from [<c0027844>] (omap_hwmod_for_each+0x34/0x60) > > [ 0.188613] [<c0027844>] (omap_hwmod_for_each) from [<c08b7d04>] (__omap_hwmod_setup_all+0x24/0x40) > > [ 0.188638] [<c08b7d04>] (__omap_hwmod_setup_all) from [<c00098a4>] (do_one_initcall+0x80/0x1e0) > > [ 0.188675] [<c00098a4>] (do_one_initcall) from [<c08a9ec0>] (kernel_init_freeable+0x214/0x2e4) > > [ 0.188707] [<c08a9ec0>] (kernel_init_freeable) from [<c0642f4c>] (kernel_init+0x8/0xec) > > [ 0.188737] [<c0642f4c>] (kernel_init) from [<c000f810>] (ret_from_fork+0x14/0x24) > > [ 0.188919] ---[ end trace 9e6a5f1c3af2b60d ]--- > > > > Unfortunately we cannot check of_device_is_available because timers are > > set to disabled. In this case we would not setup the timer module > > what leads to a crash during boot. > > The same issue has been encountered on AM43x-epos evm. Dave has > submitted a similar patch[1](Complete Series[2]) to avoid hwmod handling > of sudh IPs. Not sure what happened to this thread but later it was > decided not to register such IPs to hwmod using compatible properties as > done here[3]. > > Probably Dave can comment more. > > [1] https://patchwork.kernel.org/patch/5945961/ > [2] https://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg114645.html > [3] https://patchwork.kernel.org/patch/8357011/ Thanks for that hint. As I understand the final patch, the new am438x devices don't have the RTC enabled at all, so they can disable the RTC there. Unfortunately in my case the RTC is not powered by hardware design, so the chip would still support the feature and I can not do a similiar trick. Would it be possible to do something in the following form: if (!of_device_is_available(np) && !of_device_is_compatible(np, "ti,omap-counter32k")) { oh->_state = _HWMOD_STATE_DISABLED; return 0; } Or could this have bad side-effects? I haven't it tested yet. Thanks and regards, Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
