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From: Dimitris Lampridis (labis@mhl.tuc.gr)
Date: Wed Dec 15 2004 - 06:11:24 EST

On Mon, 2004-12-13 at 12:08 -0500, linux-os wrote:
> Also, PCI interrupts __must__ be level. It's in the PCI specification.
> If this IRQ level is raised, the kernel will call the registered
> interrupts. It has no choice and if it didn't work nobody would
> be able to boot. The only possibility is that somebody else is
> using the interrupt and hasn't allocated it shared, or your
> code has bug(s).
OK, so level triggered, active low it is.
The interrupt line is not shared by anyone else (right now. in the past
it did but only with other pci devices) as I can see
in /proc/interrupts, but also request_irq() is returning with success.
So no problem there. Therefore, I must agree with you, my code has

> Also, returning IRQ_NONE will force your ISR to be called repeatedly
> until the kernel is forced to shut off the ISR. It should return
> IRQ_DONE. You need to allocate the interrupt specified in the
> "dev" structure and not attempt to out-think anything. You should
> never even care what the raw configuration settings are. If your
> code looks at that stuff, it's broken.
Why returning IRQ_NONE is wrong? if it is not my interrupt but for
another driver for a device sharing the interrupt line, I should leave
it to him to return IRQ_HANDLED. No?

> struct pci_dev *pdev;
> pdev = PCI_FIND_DEVICE(PCI_ID, PCI_DEV, pdev);
> // use ioremap_nocache() for BARS.
> request_irq(pdev->irq, my_isr, SA_INTERRUPT|SA_SHIRQ, "device",
> pointer_to_your_stuff);
> pci_set_drvdata(pdev, NULL); // Not necessary
> pci_set_power_state(pdev, 0); // Now mandatory
> pci_set_master(pdev); // PLX is a master
> pci_set_dma_mask(pdev, 0xffffffffULL); // Future needs on ix86
> pci_set_mwi(pdev); // If you want
> pci_enable_device(pdev); // Remember to do this
> This __will__ initialize the PLX chip, but you still have to
> set/unmask its interrupt registers to get an interrupt.
> Both the PLX chip and the kernel code will properly handle an
> interrupt. We use these extensively here, so it's just some
> bug(s) in your code.
The only thing that didn't already exist in my code was
pci_set_power_state(pdev, 0), but it did not make any difference. the
problem persists. Do you think that there is a problem if I request the
irq line after calling pci_enable_device()? I cannot think of anything
else. Everything that you mentioned is already in my code, and yet I can
see no interrupt. Maybe it has something to do with my HW / BIOS?

Thanks a lot,
Dimitris Lampridis <labis@mhl.tuc.gr>

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