{Request IRQ/FIQ}

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rvanspaa
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Joined: Sat Nov 11, 2017 3:04 am

{Request IRQ/FIQ}

Postby rvanspaa » Sun Jun 02, 2019 6:06 am

Hi,

Perhaps I'm just too sleepy, but it looks to me as though when BCM2708GPIO_FIQ_ENABLED is enabled, and BCM2708GPIO_FIQ_BANK_NO = 1, two interrupts get set, one normal interrupt for BANK_NO = 0 (in the else branch), and the expected interrupt in the THEN branch of BANK_NO = 1.

Am I missing something?

Regards,

rvanspaa
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Ultibo
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Re: {Request IRQ/FIQ}

Postby Ultibo » Sun Jun 02, 2019 10:24 am

rvanspaa wrote:Perhaps I'm just too sleepy, but it looks to me as though when BCM2708GPIO_FIQ_ENABLED is enabled, and BCM2708GPIO_FIQ_BANK_NO = 1, two interrupts get set, one normal interrupt for BANK_NO = 0 (in the else branch), and the expected interrupt in the THEN branch of BANK_NO = 1.

Am I missing something?

Hi rvanspaa,

This is completely correct as far as we can see (we did check just to be sure in case we missed something :o)

The GPIO block on the BCM27xx SoC used in the Pi has an interrupt per bank of pins, the device actually supports 3 banks but only 2 are available on the Pi, Bank 0 is GPIO 0 to 31 and Bank 1 GPIO 32 to 54.

To make it just a little less straightforward the Pi only supports one single FIQ , that's one only for the entire peripheral block including all the standard devices like GPIO, I2C, SPI, DMA, USB etc etc. To make FIQ support work with the GPIO device we decided to add a setting that specified whether to enable it for Bank 0 or Bank 1, the other bank remains as IRQ so that all of the normal functionality still works.

While making and testing the change we did realize that an extra interrupt is available for all GPIO banks so that a single interrupt (which can be FIQ) covers every available pin, we need to adjust the architecture of the driver slightly to accommodate this so it is on the list for future updates now that it is confirmed that FIQ is a useful addition to the GPIO.

Hope that makes sense.
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rvanspaa
Posts: 27
Joined: Sat Nov 11, 2017 3:04 am

Re: {Request IRQ/FIQ}

Postby rvanspaa » Sun Jun 02, 2019 9:59 pm

Thanks for the explanation, and sorry to have troubled you. :oops:
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Ultibo
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Re: {Request IRQ/FIQ}

Postby Ultibo » Sun Jun 02, 2019 11:25 pm

rvanspaa wrote:Thanks for the explanation, and sorry to have troubled you. :oops:

No trouble at all, we really do want everyone to understand how Ultibo works so we're always happy to answer questions.
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