bcm2711 PCIe Interrupt Pins B through D not functional

Open
#4,666 5 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
linux
Domain
embedded-iot, operating-systems

Research direction

Start with arch/arm/boot/dts/bcm2711.dtsi and compare its PCIe interrupt map with the attached bcm2711-pcie-int.zip change, particularly the entries for pins B through E. Validate the map on a Raspberry Pi Compute Module 4 with PCIe peripherals using those pins, and confirm that MSI behavior remains unaffected.

Written by the indexing model from the issue text.

Description

This pertains to Linux for the Raspberry Pi version 5.10.74 and the
included Device Tree definition files. The file
"arch/arm/boot/dts/bcm2711.dtsi" only defines an interrupt for PCIe
interrupt Pin A. Devices that use interrupt Pins C, D, or E will not
function properly because they cannot request interrupts.

Existing definition of interrupt map for PCIe in "bcm2711.dtsi":

interrupt-map-mask = <0x0 0x0 0x0 0x7>;
interrupt-map = <0 0 0 1 &gicv2 GIC_SPI 143
		IRQ_TYPE_LEVEL_HIGH>;

The work around or correction to the interrupt map is this:

interrupt-map-mask = <0x0 0x0 0x0 0xFF>;
interrupt-map =
	<0 0 0 1
		&gicv2 GIC_SPI 143 IRQ_TYPE_LEVEL_HIGH>,
	<0 0 0 2
		&gicv2 GIC_SPI 144 IRQ_TYPE_LEVEL_HIGH>,
	<0 0 0 3
		&gicv2 GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>,
	<0 0 0 4
		&gicv2 GIC_SPI 146 IRQ_TYPE_LEVEL_HIGH>;

I tested this change on the Raspberry Pi Compute Module 4 and
associated IO board. There is not enough documentation for the
interrupt controllers in the BCM2711 for me to verify that the
assigned interrupt request numbers are valid. The pins do have to use
different interrupt request numbers, or the associated interrupt
handler is not called.

This problem affects any PCIe peripherals or bus multiplexers that use
interrupt Pins C through E, either directly or indirectly due to
interrupt "swizzling" (rotation). The problem does not affect the
operation of Message Signaled Interrupts (MSI) on the PCIe interface
because they use a different set of interrupt request lines.

A modified "bcm2711.dtsi" is attached. Search for initials "EWW".

bcm2711-pcie-int.zip

Dominant language
C
Stars
13.2k
Forks
5.5k
Avg merge
2d 21h
Merged PRs (30d)
21

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from raspberrypi/linux

All issues in raspberrypi/linux

Similar issues

More C issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.