Hi Rob, On Wednesday 13 of November 2013 18:50:12 Rob Herring wrote: > On 11/13/2013 06:41 PM, Tomasz Figa wrote: > > Hi Will, > > > > On Friday 25 of October 2013 14:48:52 Will Deacon wrote: > >> On Sat, Oct 19, 2013 at 03:04:22PM +0100, Tomasz Figa wrote: > >>> On Saturday 19 of October 2013 18:09:15 Sachin Kamat wrote: > >>>> Hi Tomasz, > >>>> > >>>> On 17 October 2013 18:35, Tomasz Figa <t.figa@xxxxxxxxxxx> wrote: > >>>>> Hi Sachin, > >>>>> > >>>>> On Thursday 17 of October 2013 17:33:12 Sachin Kamat wrote: > >>>>>> L2x0 cache controller is present only in Cortex-A9 based Exynos4 SoCs. > >>>>>> Thus move this function to Exynos4 early init call to avoid non-Exynos4 > >>>>>> SoCs from calling this function in multi-platform support. > >>>>> > >>>>> I believe that at the time .init_early() is called there is no ioremap() > >>>>> infrastructure working yet and so L2 cache initialization which needs > >>>>> it will cause a kernel panic. This patch worked only because currently > >>>>> there is no L2X0 controller defined in device tree sources of Exynos 4. > >>>> > >>>> It is not clear to me as to why device tree entry is required for this > >>>> to work in current form > >>>> as we call the L2X0 init function explicitly. > >>> > >>> L2x0 controller is just another IP block on the SoC. In addition its > >>> registers are memory mapped and the driver needs some way to get their > >>> location. The function being called explicitly simply scans device tree > >>> for applicable node and performs rest of the setup only if it finds one. > >>> > >>> Ideally there should be no need to call this function explicitly, as it > >>> should be called by some code based on presence of applicable device tree > >>> node. > >> > >> It's a nice idea, but you need to be careful if you start deferring this > >> stuff. Aside from the potential performance loss during early boot, I'm not > >> even sure that the l2x0_init function is safe to run with IRQs enabled. > >> > >> Will > > > > I just realised that I have not replied to your message, sorry for that. > > > > So, my intention was not deferring this, but rather making this more > > generic. In case of Exynos, we call l2x0_of_init() from an early_initcall > > which is long time already after enabling interrupts, but still before > > SMP is initialized. > > I believe SMP is enabled before any initcalls. You're almost right. Before any initcalls, except early_initcalls. This is a misleading label in init/main.c in an array of initcall names, calling initcall level 0 "early", but that should be "pure". early_initcalls are called from a different place in code - see do_pre_smp_initcalls(). > > My idea was to create a generic early_initcall in arch/arm/mm/cache-l2x0.c > > that would scan DT for applicable node, parse aux_val and aux_mask from > > such node (if found) and then initialize L2X0 without any need for > > having platform-specific code. > > > > However my concern here is whether on some platforms such platform code > > wouldn't be needed anyway. Unfortunately I don't really know enough > > about L2X0 to be able to answer this myself, at least at the moment. > > Unfortunately, non-secure mode platforms like highbank and omap have to > make platform specific smc calls. This is what I was afraid of. Still, I don't think there is no way we could mitigate this. Maybe firmware_ops infrastructure could be used for this? I need to know more about requirements of such platforms w.r.t. L2 cache initialization to be able to say anything more, though. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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