Re: [PATCH v2 00/21] irqchip: gic: killing gic_arch_extn and co, slowly

[santosh shilimkar <santosh.shilimkar@oracle.com>]

Marc,

On 1/7/2015 9:42 AM, Marc Zyngier wrote:
> The gic_arch_extn hack that a number of platform use has been nagging
> me for too long. It is only there for the benefit of a few platform,
> and yet it impacts all GIC users. Moreover, it gives people the wrong
> idea ("let's use it to put some new custom hack in there"...).
>
> But now that stacked irq domains have landed in -next, the time has
> come for gic_arch_extn to meet the Big Bit Bucket.
>
> This patch series takes several steps towards the elimination of
> gic_arch_extn:
>
> - moves Tegra's legacy interrupt controller support to
>    drivers/irqchip, implementing a stacked domain on top of the
>    standard GIC.
>
> - OMAP, imx6 and exynos are also converted to stacked domains, but
>    their implementation is left in place (the code is far too
>    intricately mixed with other details of the platform for me to even
>    try to move it). Some OMAP variants get a special treatment as we
>    also kill the crossbar horror (more on that below).
>
> - shmobile, ux500 and zynq are only slightly modified.
>
> - The GIC itself is cleaned up, and some other bits and bobs are
>    adjusted for a good measure.
>
> About the TI crossbar:
>
> - The allocation of interrupts in this domain is fairly similar to
>    what we do for MSI (see the GICv2m driver), and stacked domains have
>    proved to be a fitting solution.
>
> - The current description in DT is currently entierely inaccurate, and
>    as we already broke it for the OMAP WUGEN block, we might as well do
>    it again for the TI crossbar.
>
> - The way crossbar, WUGEN and GIC interract is quite complex (this is
>    effectively a stack of three interrupt controllers with interesting
>    exceptions and braindead routing), and stacked domains are the right
>    abstraction for that.
>
> - Other platforms (Freescale Vybrid) are starting to come up with the
>    same type of things, and it'd be good to avoid them following the
>    same broken model.
>
> - It removes a few lines from the code base so it can't completely be
>    a bad idea!
>
> So this patch series does exactly that: make the crossbar a stacked
> interrupt controller that only takes care of setting up the routing,
> fix the DTs to represent the actual HW, and remove a bit of the
> craziness from the GIC code.
>
> It is worth realizing that:
>
> - I haven't been able to test this as much as I would have wanted to
>    (it's only been tested on tegra2 and omap5).
>
> - I've created DT bindings when needed, updated existing ones, but I
>    haven't created a binding for platforms that already used an
>    undocumented one (imx6, I'm looking at you).
>
> - I've relaxed quite a bit of the locking in the GIC code. I believe
>    this is safe, but someone else should give it a long hard look.
>
> - This actively *breaks* existing setups. Once you boot a new kernel
>    with an old DT, suspend/resume *will* be broken. Old kernels on a
>    new DT won't even boot! You've been warned. This really outline the
>    necessity of actually describing the HW in device trees...
>
> As for the patches, they are on top of 3.19-rc3.
>
> I've pushed the code to:
> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/die-gic-arch-extn-die-die-die
>
> Comments welcome,
>
> 	 M.
>
> Marc Zyngier (21):
>    ARM: tegra: irq: nuke leftovers from non-DT support
>    irqchip: tegra: add DT-based support for legacy interrupt controller
>    ARM: tegra: skip gic_arch_extn setup if DT has a LIC node
>    ARM: tegra: update DTs to expose legacy interrupt controller
>    DT: tegra: add binding for the legacy interrupt controller
>    ARM: tegra: remove old LIC support
>    genirq: Add irqchip_set_wake_parent
>    irqchip: crossbar: convert dra7 crossbar to stacked domains
>    DT: update ti,irq-crossbar binding
>    irqchip: GIC: get rid of routable domain
>    DT: arm,gic: kill arm,routable-irqs
>    ARM: omap: convert wakeupgen to stacked domains
>    DT: omap4/5: add binding for the wake-up generator
>    ARM: imx6: convert GPC to stacked domains
>    ARM: exynos4/5: convert pmu wakeup to stacked domains
>    DT: exynos: update PMU binding
>    irqchip: gic: add an entry point to set up irqchip flags
>    ARM: shmobile: remove use of gic_arch_extn.irq_set_wake
>    ARM: ux500: switch from gic_arch_extn to gic_set_irqchip_flags
>    ARM: zynq: switch from gic_arch_extn to gic_set_irqchip_flags
>    irqchip: gic: Drop support for gic_arch_extn
>
Thanks a lot for killing those gic_arch_extn and cross-bar with
newly added stacked domains. It cleans up the GIC code for better.
Feel free to add my ack if you need one.

Acked-by: Santosh Shilimkar <ssantosh@kernel.org>

Regards,
Snatosh