From: Marc Zyngier <firstname.lastname@example.org> To: Thomas Gleixner <email@example.com> Cc: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Thierry Reding <email@example.com>, Jonathan Hunter <firstname.lastname@example.org>, Dmitry Osipenko <email@example.com>, Sowjanya Komatineni <firstname.lastname@example.org>, Venkat Reddy Talla <email@example.com>, firstname.lastname@example.org Subject: Re: [PATCH v2 1/4] genirq/irqdomain: Allow partial trimming of irq_data hierarchy Date: Wed, 07 Oct 2020 09:53:49 +0100 Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 2020-10-07 09:05, Marc Zyngier wrote: > On 2020-10-06 21:39, Thomas Gleixner wrote: >> On Tue, Oct 06 2020 at 11:11, Marc Zyngier wrote: >>> It appears that some HW is ugly enough that not all the interrupts >>> connected to a particular interrupt controller end up with the same >>> hierarchy repth (some of them are terminated early). This leaves >> >> depth? >> >>> the irqchip hacker with only two choices, both equally bad: >>> >>> - create discrete domain chains, one for each "hierarchy depth", >>> which is very hard to maintain >>> >>> - create fake hierarchy levels for the shallow paths, leading >>> to all kind of problems (what are the safe hwirq values for these >>> fake levels?) >>> >>> Instead, let's offer the possibility to cut short a single interrupt >> >> s/let's offer/implement/ > > Thanks for that, I'll fix it locally. > > [...] > >> This is butt ugly, really. Especially the use case where the tegra PMC >> domain removes itself from the hierarchy from .alloc() > > I don't disagree at all. It is both horrible and dangerous. > > My preference would have been to split the PMC domain into discrete > domains, each one having having its own depth. But that's incredibly > hard to express in DT, and would break the combination of old/new > DT and kernel. > >> That said, I don't have a better idea either. Sigh... > > A (very minor) improvement would be to turn the trim call in the PMC > driver into > a flag set in the first invalid irq_data structure, and let > __irq_domain_alloc_irqs() do the dirty work. > > Still crap, but at least would prevent some form of abuse. Thoughts? Actually, I wonder whether we can have a more general approach: A partial hierarchy that doesn't have an irq_data->chip pointer populated cannot be valid. So I wonder if the least ugly thing to do is to just drop any messing about in the PMC driver, and instead to let __irq_domain_alloc_irqs() do the culling, always, by looking for a NULL pointer in irq_data->chip. Not any less ugly, but at least doesn't need any driver intervention. M. -- Jazz is not dead. It just smells funny...
next prev parent reply index Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-06 10:11 [PATCH v2 0/4] soc/tegra: Prevent the PMC driver from corrupting interrupt routing Marc Zyngier 2020-10-06 10:11 ` [PATCH v2 1/4] genirq/irqdomain: Allow partial trimming of irq_data hierarchy Marc Zyngier 2020-10-06 20:39 ` Thomas Gleixner 2020-10-07 8:05 ` Marc Zyngier 2020-10-07 8:53 ` Marc Zyngier [this message] 2020-10-07 12:23 ` Marc Zyngier 2020-10-07 12:54 ` Thomas Gleixner 2020-10-06 10:11 ` [PATCH v2 2/4] gpio: tegra186: Allow optional irq parent callbacks Marc Zyngier 2020-10-06 10:11 ` [PATCH v2 3/4] soc/tegra: pmc: " Marc Zyngier 2020-10-06 10:11 ` [PATCH v2 4/4] soc/tegra: pmc: Don't create fake interrupt hierarchy levels Marc Zyngier 2020-10-06 12:39 ` [PATCH v2 0/4] soc/tegra: Prevent the PMC driver from corrupting interrupt routing Thierry Reding
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