From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 09/16] ARM: imx6: convert wakeupgen to stacked domains
Date: Mon, 08 Dec 2014 11:18:12 +0000 [thread overview]
Message-ID: <548588F4.6060309@arm.com> (raw)
In-Reply-To: <67e8ccd2cb9fbcc3598904a441c8a2d0@agner.ch>
Hi Stephan,
On 06/12/14 16:08, Stefan Agner wrote:
> On 2014-12-02 17:58, Marc Zyngier wrote:
>> IMX6 has been (ab)using the gic_arch_extn to provide
>> wakeup from suspend, and it makes a lot of sense to convert
>> this code to use stacked domains instead.
>>
>> This patch does just this, updating the DT files to actually
>> reflect what the HW provides.
>>
>> BIG FAT WARNING: because the DTs were so far lying by not
>> exposing the fact that the GPC block is actually the first
>> interrupt controller in the chain, kernels with this patch
>> applied wont have any suspend-resume facility when booted
>> with old DTs, and old kernels with updated DTs won't even boot.
>>
>
> Not sure this is entirely true. I don't think that GPC block is really
> in the chain of the interrupts for normal interrupt delivery. This is
> tested to be _not_ true for Vybird (which has also a GPC block and seems
> to be quite similar). I can mask an interrupt in GPC_IMR2 for instance
> and it still gets delivered to the GIC. However, the registers need to
> be unmasked to deliver wake-up events.
Well, if it has an influence on the delivery of interrupts in the
wake-up case, we need to take care of it.
> In the GPC_IMRx register description of Vybrid this sentence actually
> states what I observe: "This register is used to mask certain interrupts
> if they are not desired to be a source of
> wake up during STOP mode.". However, this sentence is not there in the
> i.MX6 RM. But the drawing in Chapter 27.1 (GPC, Overview) suggests to
> me, that it is implemented like I see it in Vybrid. So I'm not
> completely sure about this, and I don't have hardware handy to test
> this...
My copy of the TRM has the following wording: "GPC determines wake-up
irq for exiting STOP mode", and the diagram just below has some
indication of the interrupts being used to generate a wake-up signal.
> I'm aware that the code did something different before. Not sure whether
> this refactoring would look differently if my suspicion holds true. I
> guess even if it is only wake-up capabilities, we would use stacked IRQ
> domain and just implement the wake-up part...?
Very much so. My (limited) understanding of the HW:
- GPC is placed before the GIC, and derives a wake-up signal based on a
mask and an enable signal (most probably the STOP state).
- It always forwards interrupts to the GIC.
- When STOP is asserted, the GIC is offline
So we can see this as either
- two parallel interrupt controllers
- two cascaded interrupt controllers
The first case cannot be represented in DT (an interrupt can only have a
single interrupt parent). so we're left with the second option, which is
a good enough approximation IMHO. Better than not describing it, anyway.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2014-12-08 11:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-02 16:58 [PATCH 00/16] irqchip: gic: killing gic_arch_extn, slowly Marc Zyngier
2014-12-02 16:58 ` [PATCH 01/16] ARM: tegra: irq: nuke leftovers from non-DT support Marc Zyngier
2014-12-02 16:58 ` [PATCH 02/16] irqchip: tegra: add DT-based support for legacy interrupt controller Marc Zyngier
2014-12-02 16:58 ` [PATCH 03/16] ARM: tegra: skip gic_arch_extn setup if DT has a LIC node Marc Zyngier
2014-12-02 16:58 ` [PATCH 04/16] ARM: tegra: update DTs to expose legacy interrupt controller Marc Zyngier
2014-12-02 16:58 ` [PATCH 05/16] DT: tegra: add binding for the " Marc Zyngier
2014-12-02 16:58 ` [PATCH 06/16] ARM: tegra: remove old LIC support Marc Zyngier
2014-12-02 16:58 ` [PATCH 07/16] ARM: omap: convert wakeupgen to stacked domains Marc Zyngier
2014-12-02 16:58 ` [PATCH 08/16] DT: omap4/5: add binding for the wake-up generator Marc Zyngier
2014-12-02 16:58 ` [PATCH 09/16] ARM: imx6: convert wakeupgen to stacked domains Marc Zyngier
2014-12-06 16:08 ` Stefan Agner
2014-12-08 11:18 ` Marc Zyngier [this message]
2014-12-02 16:58 ` [PATCH 10/16] ARM: exynos4/5: convert pmu wakeup " Marc Zyngier
2014-12-02 16:58 ` [PATCH 11/16] DT: exynos: update PMU binding Marc Zyngier
2014-12-02 16:58 ` [PATCH 12/16] irqchip: gic: add an entry point to set up irqchip flags Marc Zyngier
2014-12-02 16:58 ` [PATCH 13/16] ARM: shmobile: remove use of gic_arch_extn.irq_set_wake Marc Zyngier
2014-12-04 6:39 ` Simon Horman
2014-12-04 8:57 ` Marc Zyngier
2014-12-04 11:46 ` Simon Horman
2014-12-02 16:58 ` [PATCH 14/16] ARM: ux500: switch from gic_arch_extn to gic_set_irqchip_flags Marc Zyngier
2014-12-03 13:52 ` Linus Walleij
2014-12-02 16:58 ` [PATCH 15/16] ARM: zynq: " Marc Zyngier
2014-12-02 16:58 ` [PATCH 16/16] irqchip: gic: Drop support for gic_arch_extn Marc Zyngier
2014-12-03 14:30 ` [PATCH 00/16] irqchip: gic: killing gic_arch_extn, slowly Arnd Bergmann
2014-12-03 14:59 ` Marc Zyngier
2014-12-03 20:32 ` Arnd Bergmann
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