arch/arm64/bcm2711: DMA driver implementation - #19815
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This commit introduces support for the BCM2711's 16 DMA channels, including the 4 DMA Lite and 4 DMA4 channels. It uses the NuttX DMA standard upper-half for compatibility with other drivers. The intention is for the majority of these channels to be used internally by other BCM2711 peripheral drivers. As such, each peripheral should be allocated an appropriate channel for its exclusive use (i.e. DMA4 channels for intensive peripherals like EMMC, frame buffer and networking, DMA Lite for low-data peripherals like a UART console).
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Workflows cancelled since this is very much a WIP. |
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Aug 12, 2026
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| #define BCM_DMA(n) (BCM_DMA0_BASE + 0x100 * (n)) | ||
| #define BCM_DMA15 (BCM_DMA15_BASE) |
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@linguini1 why to create a separated BCM_DMA15? Can't BCM_DMA(15) be used?
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NOTE
This PR is a WIP. I am opening it as a draft because:
It looks like I had discovered this a while ago on #8773 but never heard back from the author. If anyone has used this DMA driver, or anyone at Xiaomi might be willing to document it/provide a test application to verify correctness of my driver that would be awesome!
Summary
This commit introduces support for the BCM2711's 16 DMA channels, including the 4 DMA Lite and 4 DMA4 channels. It uses the NuttX DMA standard upper-half for compatibility with other drivers. The intention is for the majority of these channels to be used internally by other BCM2711 peripheral drivers. As such, each peripheral should be allocated an appropriate channel for its exclusive use (i.e. DMA4 channels for intensive peripherals like EMMC, frame buffer and networking, DMA Lite for low-data peripherals like a UART console).
Impact
Pre-cursor to a network driver (#16953) for the RPi4B Ethernet, which is the last milestone for my GSoC contract #18507.
Full support for DMA interfaces which should provide a large speedup for all
peripherals who later integrate this approach.
Testing
N/A, this is still a draft.