overlays: Add pcie-32bit-dma overlay #4216
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pelwell
reviewed
Mar 15, 2021
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Doh - and the name of the overlay is wrong in the README. |
In order to accommodate full PCI DMA access to memory on newer BCM2711 revisions, we're forced to map PCIe's view of physical memory with an offset. This offset makes DMA addressing dependent on having 64bit support on the PCI device's side. Which isn't always the case. In order to mitigate this, introduce the pcie-32bit-dma overlay which will forbid firmware from updating the default inbound memory window. The default setting, albeit limited to accessing the lower 3GB of memory, will allow for 32bit DMA addresses at the expense of having to bounce buffers. Link: raspberrypi#4197 Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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Fixed! It's amazing how I consistently get this sort of thing wrong... |
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Thanks - I'll back-port to 5.10. |
popcornmix
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Mar 23, 2021
kernel: Make rpi poe fan less noisy in cool environments See: raspberrypi/linux#4222 kernel: overlays: Add pcie-32bit-dma overlay See: raspberrypi/linux#4216 kernel: ARM: dts: bcm2711: Add aliases for additional SPIs kernel: Revert i2c: bcm2835: Handle untimely DONE signal See: Hexxeh/rpi-firmware#261
popcornmix
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Mar 23, 2021
kernel: Make rpi poe fan less noisy in cool environments See: raspberrypi/linux#4222 kernel: overlays: Add pcie-32bit-dma overlay See: raspberrypi/linux#4216 kernel: ARM: dts: bcm2711: Add aliases for additional SPIs kernel: Revert i2c: bcm2835: Handle untimely DONE signal See: #261
This was referenced Jan 25, 2024
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In order to accommodate full PCI DMA access to memory on newer BCM2711
revisions, we're forced to map PCIe's view of physical memory with an
offset. This offset makes DMA addressing dependent on having 64bit
support on the PCI device's side. Which isn't always the case.
In order to mitigate this, introduce the pcie-32bit-dma overlay which
will forbid firmware from updating the default inbound memory window.
The default setting, albeit limited to accessing the lower 3GB of
memory, will allow for 32bit DMA addresses at the expense of having to
bounce buffers.
Link: #4197
Signed-off-by: Nicolas Saenz Julienne nsaenzjulienne@suse.de