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Fri, 12 Jun 2026 01:47:49 -0700 (PDT) Date: Fri, 12 Jun 2026 09:47:47 +0100 From: William Bright To: Vladimir Zapolskiy Cc: Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Ram Boukobza , Tendai Makumire Subject: Re: [PATCH v2] arm64: dts: qcom: sm8550: add SDHC4 controller node Message-ID: References: <20260427-sm8550-sdhc4-support-v2-1-a4241f43ecd5@imd-tec.com> <5a5cbf8f-07ef-419a-8d30-c1b0b2786312@linaro.org> <00643a25-040a-4bec-8324-f52b30d84f9f@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <00643a25-040a-4bec-8324-f52b30d84f9f@linaro.org> On Thu, Jun 11, 2026 at 10:48:34AM +0300, Vladimir Zapolskiy wrote: > Looks like the SDHC driver behaves expectedly then. For me it's hard to say > what may be the rootcause, I believe the lower bus frequency should be fine, > so it sounds like a hardware issue, but could it be PCB/board specific one? > > If you find a chance to copy the SDHC driver (and its small dependencies) > from Android and test it on your board, and if it also fails, then it might > be well concluded that something is wrong with hardware, still it won't be > quite convincing that the SoC SDHC is to blame here. > > Hope it helps. > > -- > Best wishes, > Vladimir My colleague Tendai () had the same issue with dll-tuning failing in SDR50 when working on the downstream 5.15 msm kernel [1]. It does sound like a potential SI issue so I will try the following: - Sweeping the drive-strength values for the sdhc_4 lines to see if I can find a set of values that work - Scoping the lines to check SI when performing dll-tuning, our board is very dense so this is challenging. I am guessing this patch is only acceptable to be upstreamed once we get to the bottom of why dll-tuning is failing? [1] https://github.com/imd-tec/meta-imdt-qcom/tree/kirkstone/patches/msm-kernel/files Many thanks, Will