arm64: dts: qcom: msm8939: Add missing MDSS reset

commit f73c82c855e186e9b67125e3eee743960320e43c upstream.

On most MSM8939 devices, the bootloader already initializes the display to
show the boot splash screen. In this situation, MDSS is already configured
and left running when starting Linux. To avoid side effects from the
bootloader configuration, the MDSS reset can be specified in the device
tree to start again with a clean hardware state.

The reset for MDSS is currently missing in msm8939.dtsi, which causes
errors when the MDSS driver tries to re-initialize the registers:

 dsi_err_worker: status=6
 dsi_err_worker: status=6
 dsi_err_worker: status=6
 ...

It turns out that we have always indirectly worked around this by building
the MDSS driver as a module. Before v6.17, the power domain was temporarily
turned off until the module was loaded, long enough to clear the register
contents. In v6.17, power domains are not turned off during boot until
sync_state() happens, so this is no longer working. Even before v6.17 this
resulted in broken behavior, but notably only when the MDSS driver was
built-in instead of a module.

Cc: stable@vger.kernel.org
Fixes: 61550c6c156c ("arm64: dts: qcom: Add msm8939 SoC")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250915-msm8916-resets-v1-2-a5c705df0c45@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/boot/dts/qcom/msm8939.dtsi b/arch/arm64/boot/dts/qcom/msm8939.dtsi
index effa3aaeb250540b511147e219fd875526479e14..39493f75c0dced2fe2b63e44197e80d7de831e86 100644 (file)
--- a/arch/arm64/boot/dts/qcom/msm8939.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8939.dtsi
@@ -1218,6 +1218,8 @@
 
                        power-domains = <&gcc MDSS_GDSC>;
 
+                       resets = <&gcc GCC_MDSS_BCR>;
+
                        #address-cells = <1>;
                        #size-cells = <1>;
                        #interrupt-cells = <1>;