Re: [GIT pull] irq updates for 4.13

From: Geert Uytterhoeven
Date: Wed Jul 12 2017 - 04:01:03 EST

Hi Grygorii,

On Tue, Jul 11, 2017 at 5:39 PM, Grygorii Strashko
<grygorii.strashko@xxxxxx> wrote:
> On 07/11/2017 09:41 AM, Thomas Gleixner wrote:
>> On Tue, 11 Jul 2017, Tony Lindgren wrote:
>>> * Thomas Gleixner <tglx@xxxxxxxxxxxxx> [170711 02:48]:
>>> And "external abort on non-linefetch" means something is not clocked
>>> in this case. The following alone makes things boot for me again, but I don't
>>> quite follow what has now changed with the ordering.. Thomas, any ideas?
>> Ah. Now that makes sense.
>> Unpatched the ordering is:
>> chip_bus_lock(desc);
>> irq_request_resources(desc);
>> Now the offending change reordered the calls. OMAP gpio has:
>> omap_gpio_irq_bus_lock()
>> pm_runtime_get_sync(bank->chip.parent);
>> So that at least explains the error. So that omap gpio irq chip (ab)uses
>> the bus_lock() callback to do runtime power management. Sigh, I did not
>> expect that. Let me have a deeper look if that's OMAP only or whether this
>> happens in other places as well.
> It was the only one way to power on GPIO bank when the first GPIO IRQ is requested,
> as all other irqchip callbacks are under raw_lock while pm_runtime uses spinlock, as
> result on -RT it was not possible to use PM runtime in other irqchip callbacks.
> Now, I think, It might be possible to use irq_chip_pm_get(), but there is one problem -
> OMAP Power management platform code can call omap2_gpio_prepare_for_idle()/omap2_gpio_resume_after_idle()
> which expected to disable GPIO banks using PM runtime and current driver implementation
> expect to have PM runtime usage_count = 1.
> Tony, Potentially we can use pm_runtime_force_suspend()/resume() there, but they are not compatible with
> irqoff context (CPUIdle late stages).
> In other words, below patch should fix this issue, but will break CPUIdle on OMAP :(
> --
> From dfca1c806f03ad6bdd72b634d71c96d39bda2046 Mon Sep 17 00:00:00 2001
> From: Grygorii Strashko <grygorii.strashko@xxxxxx>
> Date: Tue, 11 Jul 2017 10:36:23 -0500
> Subject: [PATCH] gpio: omap: switch to use irq_chip_pm_get/put()
> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>

That looks similar to how gpio-rcar was fixed, which used to do the
same trick in its bus_lock() callbacks.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds