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Date: Fri, 15 Aug 2014 11:10:07 +0200 From: christophe leroy <christophe.leroy@....fr> To: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>, Florian Fainelli <f.fainelli@...il.com>, "David S. Miller" <davem@...emloft.net> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org> Subject: Re: Issue with commit 33c133cc7598e60976a phy: IRQ cannot be shared Le 14/08/2014 13:03, Sergei Shtylyov a écrit : > Hello. > > On 8/14/2014 10:31 AM, leroy christophe wrote: > >> I have an hardware with two ethernet interfaces, and with the two >> PHYs inside >> the same component INTEL LXT973 which has only one interrupt. >> I also have another hardware with two ethernet interfaces and two >> independant >> PHYs. But the two PHYs are wired to the same interrupt. >> This is working perfectly up to Linux 3.12. > > Hm, I'm surprised it works. Are you sure you're getting interrupts > from both PHYs? Because if both Ethernet controllers are active > simultaneously, only the first registered PHY IRQ handler should get > all the interrupts. Yes it works. Why should only the first one get the interrupts ? handle_irq_event_percpu() (from kernel/irq/handle.c, extract below) calls all handlers regardless of whether they answer IRQ_NONE or IRQ_HANDLED. The break applies to the switch(), not to the while(). So all handlers are called. irqreturn_t handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) { irqreturn_t retval = IRQ_NONE; unsigned int flags = 0, irq = desc->irq_data.irq; do { [...] switch (res) { case IRQ_WAKE_THREAD: [...] case IRQ_HANDLED: flags |= action->flags; break; default: break; } retval |= res; action = action->next; } while (action); > >> But since your commit, introduced in Linux 3.13, my interfaces don't >> work >> anymore as the second PHYs can't register IRQ. > > Strange too, the phylib should use polling in case request_irq() > fails. Well, you are right, I didn't check closely enough, was assuming they didn't register due to the messages saying interrupt mismatch. > >> Reading the commit log, I can't really understand the reason for the >> change. > > The shared IRQ handler should check for IRQ from its device and > return IRQ_NONE if there's no IRQ active; phy_interrupt() doesn't do > that (this is pushed to the workqueue). Well, as seen above, this has no impact on whether other handlers are called or not. > >> Is it really worth it, and therefore how shall my case be handled ? > > PHY IRQs are not necessary for the phylib state machine. However, polling is less efficient than IRQs. It wastes CPU and link loss detection is slower. > >> Christophe > > WBR, Sergei > BR Christophe --- Ce courrier électronique ne contient aucun virus ou logiciel malveillant parce que la protection avast! Antivirus est active. http://www.avast.com -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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