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[2/2] arm64: dts: qcom: msm8939: Make blsp_dma controlled-remotely

Message ID 20231204-msm8916-blsp-dma-remote-v1-2-3e49c8838c8d@gerhold.net
State New
Headers
Series arm64: dts: qcom: msm8916/39: Make blsp_dma controlled-remotely |

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/msm8939-common.dtsi#L866-872

Cc: <stable@vger.kernel.org> # 6.5
Fixes: 61550c6c156c ("arm64: dts: qcom: Add msm8939 SoC")
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/msm8939.dtsi | 1 +
 1 file changed, 1 insertion(+)

Comments

Bryan O'Donoghue Dec. 4, 2023, 10:59 a.m. UTC | #1 
On 04/12/2023 11:21, Stephan Gerhold wrote:
> 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: 61550c6c156c ("arm64: dts: qcom: Add msm8939 SoC")
> 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/msm8939.dtsi | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/msm8939.dtsi b/arch/arm64/boot/dts/qcom/msm8939.dtsi
> index 95610a32750a..9eb8f1ceee99 100644
> --- a/arch/arm64/boot/dts/qcom/msm8939.dtsi
> +++ b/arch/arm64/boot/dts/qcom/msm8939.dtsi
> @@ -1761,6 +1761,7 @@ blsp_dma: dma-controller@7884000 {
>   			clock-names = "bam_clk";
>   			#dma-cells = <1>;
>   			qcom,ee = <0>;
> +			qcom,controlled-remotely;
>   		};
>   
>   		blsp_uart1: serial@78af000 {
> 

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
diff mbox series

Patch

diff --git a/arch/arm64/boot/dts/qcom/msm8939.dtsi b/arch/arm64/boot/dts/qcom/msm8939.dtsi
index 95610a32750a..9eb8f1ceee99 100644
--- a/arch/arm64/boot/dts/qcom/msm8939.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8939.dtsi
@@ -1761,6 +1761,7 @@  blsp_dma: dma-controller@7884000 {
 			clock-names = "bam_clk";
 			#dma-cells = <1>;
 			qcom,ee = <0>;
+			qcom,controlled-remotely;
 		};
 
 		blsp_uart1: serial@78af000 {