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Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled

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On Wed, Apr 27, 2016 at 10:57:21AM +0800, Dong Aisheng wrote:
> 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.

Thanks for the info.  It sounds like that we are fixing the problem in
the wrong place, i.e. clk_pllv3_prepare().  The function does nothing
wrong, since the .prepare hook is defined to be one that can sleep.  If
we see sleep warning in a context calling clk_prepare(), that probably
means we shouldn't make the function call from that context.

Shawn

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Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-21 06:00 +0200
  Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Shawn Guo <shawnguo@kernel.org> - 2016-04-26 03:30 +0200
    Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-26 08:00 +0200
      Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Shawn Guo <shawnguo@kernel.org> - 2016-04-26 11:30 +0200
      Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Lucas Stach <l.stach@pengutronix.de> - 2016-04-26 11:40 +0200
        Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-26 13:20 +0200
          Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-26 13:30 +0200
            Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Shawn Guo <shawnguo@kernel.org> - 2016-04-27 04:00 +0200
              Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-27 04:50 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Fabio Estevam <festevam@gmail.com> - 2016-04-27 05:00 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Stefan Agner <stefan@agner.ch> - 2016-04-27 09:40 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-27 11:00 +0200
              Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-27 05:00 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Shawn Guo <shawnguo@kernel.org> - 2016-04-27 09:30 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Stefan Agner <stefan@agner.ch> - 2016-04-27 09:40 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-27 10:50 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Stefan Agner <stefan@agner.ch> - 2016-04-27 09:40 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Dong Aisheng <dongas86@gmail.com> - 2016-04-27 11:00 +0200
                Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Thomas Gleixner <tglx@linutronix.de> - 2016-04-27 12:20 +0200

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