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[144.178.202.139]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b26e36ae75dsm15882366b.8.2025.09.19.02.49.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Sep 2025 02:49:21 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 19 Sep 2025 11:49:20 +0200 Message-Id: Cc: "Vincent Knecht" , "Bryan O'Donoghue" , "Rob Herring" , "Krzysztof Kozlowski" , "Conor Dooley" , , , Subject: Re: [PATCH 1/3] arm64: dts: qcom: msm8916: Add missing MDSS reset From: "Luca Weiss" To: "Stephan Gerhold" , "Bjorn Andersson" , "Konrad Dybcio" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20250915-msm8916-resets-v1-0-a5c705df0c45@linaro.org> <20250915-msm8916-resets-v1-1-a5c705df0c45@linaro.org> In-Reply-To: <20250915-msm8916-resets-v1-1-a5c705df0c45@linaro.org> Hi Stephan, On Mon Sep 15, 2025 at 3:28 PM CEST, Stephan Gerhold wrote: > On most MSM8916 devices (aside from the DragonBoard 410c), the bootloader > already initializes the display to show the boot splash screen. In this > situation, MDSS is already configured and left running when starting Linu= x. > To avoid side effects from the bootloader configuration, the MDSS reset c= an > be specified in the device tree to start again with a clean hardware stat= e. > > The reset for MDSS is currently missing in msm8916.dtsi, which causes > errors when the MDSS driver tries to re-initialize the registers: > > dsi_err_worker: status=3D6 > dsi_err_worker: status=3D6 > dsi_err_worker: status=3D6 > ... > > It turns out that we have always indirectly worked around this by buildin= g > the MDSS driver as a module. Before v6.17, the power domain was temporari= ly > 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 thi= s > resulted in broken behavior, but notably only when the MDSS driver was > built-in instead of a module. Do you have a link to the patch that causes this behavior? I've tried looking through the git log for drivers/gpu/drm/msm/ but couldn't find anything that looks relevant. FWIW a similar change to this was also necessary for sc7280 (as done by Bjorn) and for sm6350 (will send the patches very soon). And happily enough for me, with v6.17 and that reset, a long-standing issue on sm7225-fairphone-fp4 has been resolved that the display init seems to somehow fail the first time after bootup, with the screen needing to be turned off once and back on to work. I traced this back to some power domain behavior as well back then. > "mdss_gdsc needs to be off before mdss/dpu probe, this can happen with > genpd_power_off_unused but not guaranteed" Anyways, I'm hoping this is not just a coincidence it works now but will stay working on my device. Just the reset in the past didn't seem to affect anything. Regards Luca > > Cc: stable@vger.kernel.org > Fixes: 305410ffd1b2 ("arm64: dts: msm8916: Add display support") > Signed-off-by: Stephan Gerhold > --- > arch/arm64/boot/dts/qcom/msm8916.dtsi | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi b/arch/arm64/boot/dts/= qcom/msm8916.dtsi > index b50c7e6e0bfcd35ab4f8b84aeabe214fd60e8d7c..de0c10b54c86c7795b7a0d1ec= d80652e60e117b6 100644 > --- a/arch/arm64/boot/dts/qcom/msm8916.dtsi > +++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi > @@ -1562,6 +1562,8 @@ mdss: display-subsystem@1a00000 { > =20 > interrupts =3D ; > =20 > + resets =3D <&gcc GCC_MDSS_BCR>; > + > interrupt-controller; > #interrupt-cells =3D <1>; > =20