Messages in this thread | | | Date | Wed, 27 Apr 2016 10:57:21 +0800 | Subject | Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled | From | Dong Aisheng <> |
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On Wed, Apr 27, 2016 at 9:58 AM, Shawn Guo <shawnguo@kernel.org> wrote: > On Tue, Apr 26, 2016 at 07:27:03PM +0800, Dong Aisheng wrote: >> Shawn, >> What's your suggestion? > > I think this needs more discussion, and I just dropped Stefan's patch > from my tree. > > We need to firstly understand why this is happening. The .prepare hook > is defined to be non-atomic context, and so that we call sleep function > in there. We did everything right. Why are we getting the warning? If > I'm correct, this warning only happens on i.MX7D. Why is that? >
Why Stefan's patch works (checking irqs_disabled()) is because during kernel time init, the irq is still not enabled. It fixes the issue indirectly. See: asmlinkage __visible void __init start_kernel(void) { /* * Set up the scheduler prior starting any interrupts (such as the * timer interrupt). Full topology setup happens at smp_init() * time - but meanwhile we still have a functioning scheduler. */ sched_init(); ............. time_init(); .............. WARN(!irqs_disabled(), "Interrupts were enabled early\n"); early_boot_irqs_disabled = false; local_irq_enable(); }
The issue can only happen when PLL enable causes a schedule during imx_clock_init(). Not all PLL has this issue. The issue happens on MX7D pll_audio_main_clk/pll_video_main_clk which requires more delay time and cause usleep. Because clk framework does not support MX7D clock types (operation requires parents on), we simply enable all clocks in imx7d_clocks_init().
If apply my this patch series: https://lkml.org/lkml/2016/4/20/199 The issue can also be gone.
Regards Dong Aisheng
> Shawn
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