linux-kernel - Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from binding document

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Date:	Fri, 18 Mar 2016 12:42:41 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Benoît Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Kumar Gala" <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	"Thierry Reding" <thierry.reding@...il.com>,
	Kevin Hilman <khilman@...nel.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	<linux-tegra@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from
 binding document


On 18/03/16 12:05, Geert Uytterhoeven wrote:
> Hi Jon,
> 
> On Fri, Mar 18, 2016 at 11:56 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>> On 18/03/16 10:52, Geert Uytterhoeven wrote:
>>> On Fri, Mar 18, 2016 at 11:13 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>>>> On 18/03/16 09:13, Geert Uytterhoeven wrote:
>>>>> On Thu, Mar 17, 2016 at 3:19 PM, Jon Hunter <jonathanh@...dia.com> wrote:
>>>>>> Commit afbbd2338176 ("irqchip/gic: Document optional Clock and Power
>>>>>> Domain properties") documented optional clock and power-dmoain properties
>>>>>> for the ARM GIC. Currently, there are no users of these and for the
>>>>>> Tegra210 Audio GIC (based upon the GIC-400) there are two clocks, a
>>>>>> functional clock and interface clock, that need to be enabled.
>>>>>
>>>>> The reason that there are no users for this is twofold:
>>>>>   1. The GIC driver doesn't have Runtime PM support yet,
>>>>>   2. There was no clean way to prevent the GIC's clock from being disabled.
>>>>> Due to this, adding the clocks to the DTSes would mean that they will be
>>>>> disabled during boot up as unused clocks, leading to a system lock-up.
>>>>>
>>>>> I had hoped your series would fix part 1. I gave it a try on r8a7791/koelsch,
>>>>> but unfortunately it seems the platform driver only supports non-root
>>>>> controllers, while the r8a7791 GIC is the primary one...
>>>>
>>>> Can you try making the following change ...
>>>
>>> Thanks! I gave it a try, but no difference.
>>
>> I assume you added the appropriate compatible flag? Any more details you
> 
> Doh... bad assumption... Silly me.
> 
>> can share about why it is not working? Is it not registered early enough?
> 
> With
> 
> +       { .compatible = "arm,gic-400", },
> 
> the kernel no longer crashes due to accessing the GIC registers while the
> GIC module clock is disabled.
> 
> However, the system doesn't boot completely, and time outs on SPI transfers
> make me believe interrupts are not working.
> Both with and without "the following change".

Yes, I recall now why I did not support primary controllers and it is
because you need to call set_smp_cross_call() (for SMP) and
set_handle_irq(). Both of which are located in the __init section and
need to be called early during boot. So to make this work for primary
controllers, more work would need to be done.

Jon