On 26.7.2016 08:32, Maxime Ripard wrote: > On Thu, Jul 21, 2016 at 11:52:15AM +0200, Ondřej Jirman wrote: >>>>> If so, then yes, trying to switch to the 24MHz oscillator before >>>>> applying the factors, and then switching back when the PLL is stable >>>>> would be a nice solution. >>>>> >>>>> I just checked, and all the SoCs we've had so far have that >>>>> possibility, so if it works, for now, I'd like to stick to that. >>>> >>>> It would need to be tested. U-boot does the change only once, while the >>>> kernel would be doing it all the time and between various frequencies >>>> and PLL settings. So the issues may show up with this solution too. >>> >>> That would have the benefit of being quite easy to document, not be a >>> huge amount of code and it would work on all the CPUs PLLs we have so >>> far, so still, a pretty big win. If it doesn't, of course, we don't >>> really have the choice. >> >> It's probably more code though. It has to access different register from >> the one that is already defined in dts, which would add a lot of code >> and require dts changes. The original patch I sent is simpler than that. > > Why?
Because I don't understand internals of clk subsystem that much. :) So my guess might be wrong. Wens send patches implementing clock source switching in the new CCU code, so hopefully it will work. Ultimately it's a hack. Some internal parts of the soc may still get into out of the bounds operating state even if they are gated off from other parts of the SoC, via clock multiplexing, by improper factors change procedure. So it doesn't really matter which is more concise in code. As long as one solution is wrong and other is proper. Anyway, I'll try with wens's patches, later and see if I trigger some instability or not. > You can use container_of to retrieve the parent structure of the clock > notifier, and then you get a ccu_common structure pointer, with the > CCU base address, the clock register, its lock, etc. > > Look at what is done in drivers/clk/meson/clk-cpu.c. It's like 20 LoC. > > I don't really get why anything should be changed in the DT, or why it > would add a lot of code. Or maybe we're not talking about the same > thing? > > Maxime > -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
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