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[1/2] arm64: dts: qcom: msm8916: Make blsp_dma controlled-remotely

Message ID 20231204-msm8916-blsp-dma-remote-v1-1-3e49c8838c8d@gerhold.net
State Accepted
Commit 7c45b6ddbcff01f9934d11802010cfeb0879e693
Headers show
Series [1/2] arm64: dts: qcom: msm8916: Make blsp_dma controlled-remotely | expand

Commit Message

Stephan Gerhold Dec. 4, 2023, 10:21 a.m. UTC
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/msm8916.dtsi#L1466-1472

Cc: <stable@vger.kernel.org> # 6.5
Fixes: a0e5fb103150 ("arm64: dts: qcom: Add msm8916 BLSP device nodes")
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
---
This should only be backported to v6.5+ since it depends on commit
8975dd41a9db ("dmaengine: qcom: bam_dma: allow omitting
num-{channels,ees}") which landed in v6.5.
---
 arch/arm64/boot/dts/qcom/msm8916.dtsi | 1 +
 1 file changed, 1 insertion(+)
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Patch

diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi b/arch/arm64/boot/dts/qcom/msm8916.dtsi
index e8a14dd7e7c2..7f8327b0dbdb 100644
--- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
@@ -2155,6 +2155,7 @@  blsp_dma: dma-controller@7884000 {
 			clock-names = "bam_clk";
 			#dma-cells = <1>;
 			qcom,ee = <0>;
+			qcom,controlled-remotely;
 		};
 
 		blsp_uart1: serial@78af000 {