On Tuesday 19 March 2013 06:53 AM, Mike Turquette wrote: > Quoting Tony Lindgren (2013-03-18 09:37:58) >> * Rajendra Nayak <rnayak@xxxxxx> [130318 01:25]: >>> On Friday 15 March 2013 09:50 PM, Tony Lindgren wrote: >>>> * Rajendra Nayak <rnayak@xxxxxx> [130315 05:31]: >>>>> On Thursday 14 March 2013 10:36 PM, Tony Lindgren wrote: >>>>>> * Rajendra Nayak <rnayak@xxxxxx> [130314 05:44]: >>>>>>> OMAP clock inits happen quite early, even before the slab is available. >>>>>>> As part of the clock init, the common clock core tries to cache parent >>>>>>> pointers (if not passed by the caller registering the clock) which >>>>>>> fails in case of OMAP since the slab isn't initied. >>>>>>> Without CONFIG_DEBUG_SLAB enabled, this just results in the common clock core >>>>>>> retrying the caching attempt at some point later. >>>>>>> However with CONFIG_DEBUG_SLAB enabled this results in a BUG() as reported >>>>>>> in the link below by Tony.. >>>>>>> http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg85932.html >>>>>>> >>>>>>> Fix this by passing static parent pointers to the common clock core >>>>>>> while registering clocks. >>>>>> >>>>>> I wonder if we could easily fix this by initializing only some of the >>>>>> clocks that early? >>>>> >>>>> We actually don't need any clocks that early (I mean even before slab init) >>>>> We only need them before timer init. >>>> >>>> Yes and only the timer clocks at that point. The others could be initialized >>>> later on so we get console error messages without having to turn on DEBUG_LL >>>> and earlyprintk. >>> >>> but that wouldn't be possible with the hwmod dependency on clocks. We would >>> need to move the hwmod inits further down too. >>> >>>> >>>>> This isn't something specific to OMAP so I started looking at what others >>>>> in drivers/clk seem to do. >>>>> >>>>> I found imx, spear, mvebu all do their clk inits within .init_time callbacks. >>>>> tegra seems to even do it within .init_irq callback. >>>>> >>>>> Either one would work for us too :) >>>> >>>> Well I suggest init_irq as that's when we need the first clocks for timer. >>> >>> For which platforms? I instead see them being needed only by init_timer, so >>> was thinking thats a better place instead. >>> >>> For the -rc fix to fix the crash with DEBUG_SLAB, is it fine if I move *all* >>> clock inits down to init_timer (or init_irq). >> >> Sounds good to me for the -rc series. How about initialize omap_clk_init() >> function pointer in the SoC specific omap*_init_early() then just call >> omap_clk_init() in timer_init? >> >>> Splitting clocks alone would not work for now, without hwmod being moved down also. >> >> Good point. For the -rc series the sounds like your suggestion is the >> least intrusive fix and also gets us started removing few more early >> boot time dependencies. >> > > +1 for removing the early init dependencies. hwmod initialization was > the original impetus for all this static struct clk stuff. If the > initialization for hwmod and the omap clocks can be moved to a later > callback then it is the first step in removing the static data and > getting rid of clk-private.h usage. I am working on that stuff to get rid of the dependency on clk-private.h Will post some RFC soon once I have omap4 working and if the approach seems fine, will move over all of omap so you can delete the clk-private.h completely :) > > Regards, > Mike > >> Regards, >> >> Tony -- 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
