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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 [1] 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.
[1]: https://git.codelinaro.org/clo/la/kernel/msm-3.10/-/blob/LA.BR.1.2.9.1-02310-8x16.0/arch/arm/boot/dts/qcom/msm8939-common.dtsi#L866-872
Cc: stable@vger.kernel.org # 6.5
Fixes: 61550c6c15 ("arm64: dts: qcom: Add msm8939 SoC")
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20231204-msm8916-blsp-dma-remote-v1-2-3e49c8838c8d@gerhold.net
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.