Date: Sun, 19 Apr 1998 22:59:30 +0200 From: Tor Egge <Tor.Egge@idi.ntnu.no> To: gibbs@plutotech.com Cc: andreas@klemm.gtn.com, smp@FreeBSD.ORG Subject: Re: SMP Problems Message-ID: <199804192059.WAA11325@pat.idi.ntnu.no> In-Reply-To: Your message of "Sun, 19 Apr 1998 12:12:27 -0600" References: <199804191816.MAA06451@pluto.plutotech.com>
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> >It might be reasonable to ignore the polarity/trigger-mode values in > >the MP table if the APIC interrupt pin number corresponds to the > >ISA/EISA interrupt number, since ISA/EISA interrupts are active-high > >edge triggered interrupts when reaching the IOAPIC. > > The EISA spec allows level sensitive interrupts. Is this not the case for > SMP systems? Seems strange. A comments in mpapic.c says: /* * EISA IRQ's are identical to ISA irq's, regardless of * whether they are edge or level since they go through * the level/polarity converter gadget. */ This indicates that the ELCR registers (at I/O addresses 0x4d0 and 0x4d1) are relevant also in Symmetric I/O mode. The MP spec also indicates that the ELCR registers are relevant in Symmetric I/O mode, but instead of selecting between edge-triggered active-high and level-triggered active-low, the ELCR register only controls whether the interrupt signal should be inverted or not before being delivered to the PIC and IOAPIC. The polarity of any redirected PCI interrupts are not affected by the ELCR register, according to figure 5-2. Table 4.10 indicates that a `conforming' EISA level interrupt is active-low as delivered to the IOAPIC. Section 5.3.2 and figure 5-2 disagrees. Thus there are three different interpretations of how to handle an EISA level interrupt registered in the MP table as conforming with regard to polarity: - Believe the comment in mpapic.c, and handle as active-high edge interrupt. - Believe table 4.10 in the MP spec, and handle as active-low level interrupt. - Believe figure 5-2 and section 5.3.2 in the MP spec and handle as active-high level interrupt. - Tor Egge To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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