The blsp_dma controller is shared between the different subsystems, which is why it is already initialized by the firmware. We should not reinitialize it from Linux to avoid potential other users of the DMA engine to misbehave.
In mainline this can be described using the "qcom,controlled-remotely" property. In the downstream/vendor kernel from Qualcomm there is an opposite "qcom,managed-locally" property. This property is *not* set for the qcom,sps-dma@7884000 so adding "qcom,controlled-remotely" upstream matches the behavior of the downstream/vendor kernel.
Adding this seems to fix some weird issues with UART where both input/output becomes garbled with certain obscure firmware versions on some devices.
Signed-off-by: Stephan Gerhold stephan@gerhold.net --- Stephan Gerhold (2): arm64: dts: qcom: msm8916: Make blsp_dma controlled-remotely arm64: dts: qcom: msm8939: Make blsp_dma controlled-remotely
arch/arm64/boot/dts/qcom/msm8916.dtsi | 1 + arch/arm64/boot/dts/qcom/msm8939.dtsi | 1 + 2 files changed, 2 insertions(+) --- base-commit: adcad44bd1c73a5264bff525e334e2f6fc01bb9b change-id: 20231204-msm8916-blsp-dma-remote-516df8aac521
Best regards,