From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5165409B.4060505@siemens.com> Date: Wed, 10 Apr 2013 12:36:11 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <515229C4.6000805@xenomai.org> <515296C8.30806@web.de> <5152BAA3.30508@xenomai.org> <5152BC4D.8050501@siemens.com> <5152EC25.7060004@xenomai.org> <5152F489.1000106@siemens.com> <515B5154.2000802@xenomai.org> <515FEE47.90507@web.de> <51633200.8030007@xenomai.org> <51653195.1050009@xenomai.org> In-Reply-To: <51653195.1050009@xenomai.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] one-shot fasteoi irqs List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: Xenomai On 2013-04-10 11:32, Philippe Gerum wrote: > On 04/08/2013 11:09 PM, Gilles Chanteperdrix wrote: >> On 04/06/2013 11:43 AM, Jan Kiszka wrote: >> >>> On 2013-04-02 23:44, Gilles Chanteperdrix wrote: >>>> On 03/27/2013 02:30 PM, Jan Kiszka wrote: >>>> >>>>> I'm wondering now why we need this differently for the I-pipe case. >>>>> >>>>> Let's revisit what happens with a fasteoi normally: >>>>> >>>>> - it's masked only if it's a oneshot IRQ before calling the flow >>>>> handler >>>>> - it's unmasked after the flow handling if the thread was not woken up >>>>> >>>>> With I-pipe we already enter handle_fasteoi_irq with the IRQ >>>>> masked. The >>>>> conditions and spots to unmask are: >>>>> - from handle_fasteoi_irq if the thread wasn't woken up or we have >>>>> non-threaded or non-oneshot handling >>>>> - otherwise on end_irq from the handler thread >>>>> >>>>> Do you think this is correct? If so, I do not think it matches this >>>>> patch yet. >>>> >>>> >>>> Hi, >>>> >>>> here is a much simpler patch: >>>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c >>>> index 11e75d1..a1c9918 100644 >>>> --- a/kernel/irq/chip.c >>>> +++ b/kernel/irq/chip.c >>>> @@ -421,6 +421,13 @@ static inline void preflow_handler(struct >>>> irq_desc *desc) >>>> static inline void preflow_handler(struct irq_desc *desc) { } >>>> #endif >>>> >>>> +static void cond_release_fasteoi_irq(struct irq_desc *desc) >>>> +{ >>>> + if (desc->irq_data.chip->irq_release && >>>> + !irqd_irq_disabled(&desc->irq_data) && !desc->threads_oneshot) >>>> + desc->irq_data.chip->irq_release(&desc->irq_data); >>>> +} >>>> + >>>> /** >>>> * handle_fasteoi_irq - irq handler for transparent controllers >>>> * @irq: the interrupt number >>>> @@ -463,8 +470,7 @@ handle_fasteoi_irq(unsigned int irq, struct >>>> irq_desc *desc) >>>> >>>> #ifdef CONFIG_IPIPE >>>> /* XXX: IRQCHIP_EOI_IF_HANDLED is ignored. */ >>> >>> Makes me wonder what this comment wants to tell us. That there is an >>> unhandled corner case or that this is intentionally ignored? I support >>> the latter as I-pipe already does EOI when accepting the IRQ, no? Maybe >>> you can clarify that line at this chance. >> >> >> I have no idea where this comment come from. I do not think this flag >> can be handled with the I-pipe kernel, as the EOI is sent before trying >> to handle the IRQ. The only users are in arch/sparc and arch/powerpc, >> maybe Philippe knows more? >> > > Jan is right, we ignore EOI_IF_HANDLED and never send EOI from the > regular flow handler, as a consequence of doing eoi+mask when holding > the IRQ in the ipipe's flow handler. OK, then I'll write a clarification patch for that comment - to get rid of that triple X... Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux