Thread (19 messages) flat view 19 messages, 5 authors, 12d ago

Re: [PATCH 1/2] dt-bindings: net: qcom,bam-dmux: Add qcom,shikra-bam-dmux compatible

From: Stephan Gerhold <hidden>
Date: 2026-07-14 07:11:32
Also in: linux-arm-msm, linux-devicetree, lkml

On Tue, Jul 14, 2026 at 11:02:31AM +0530, Vishnu Santhosh wrote:
On platforms where the modem DMAs into the BAM-DMUX RX data buffers and
the XPU enforces per-region access control, each individually
DMA-mapped RX buffer consumes an XPU resource group. With only ~16
groups available, the per-buffer mappings exhaust the table and inbound
transfers fault.

Add qcom,shikra-bam-dmux as an additional compatible for the Shikra SoC,
paired with the generic qcom,bam-dmux fallback, so the driver can match
on it via its of_device_id table.

Co-developed-by: Deepak Kumar Singh <redacted>
Signed-off-by: Deepak Kumar Singh <redacted>
Signed-off-by: Vishnu Santhosh <redacted>
IMHO (the DT maintainers might disagree) this is not a different
BAM DMUX hardware block on Shikra, just a different firmware
configuration. I'm sure the existing SoCs also have those XPU blocks,
they just don't make use of it.

Personally, I would rather describe this with an optional "qcom,vmid"
property similar to your bam-dma patch, allowed for all SoCs.

Thanks,
Stephan
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