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Thu, 03 Sep 2026 07:40:55 -0700 (PDT) X-Received: by 2002:ac5:c84a:0:b0:5c7:d15b:5f2a with SMTP id 71dfb90a1353d-5c7d2809352mr1626554e0c.2.1788446449511; Thu, 03 Sep 2026 07:40:49 -0700 (PDT) Received: from [192.168.202.12] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-3a3705866acsm147251fa.18.2026.09.03.07.40.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Sep 2026 07:40:48 -0700 (PDT) Message-ID: Date: Thu, 3 Sep 2026 16:40:44 +0200 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/6] PCI: of: Avoid config reads for disabled bridge nodes To: sophon@radxa.com, Bjorn Helgaas , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Bartosz Golaszewski , Linus Walleij Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-gpio@vger.kernel.org, Stephen Chen , Junhao Xie References: <20260901-q8b-dts-v1-0-7de0b6a73d08@radxa.com> <20260901-q8b-dts-v1-1-7de0b6a73d08@radxa.com> <8c2eaba0-c1bd-4db0-bbc8-5ae3b3d9a13c@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTAzMDEyNyBTYWx0ZWRfX1olxuALFdK/P iW9Hs6FnDX91BieAhQpLg42yyLN/YscV6sZQeuZi30K4mRyEMo10C8EfLdTZGff8ijd2qdKjMkA OLyPvuMdaYlmdlQ4jtchmus6yGT/CzNQJ/pSH2i8Ooo8GbXxNvostmXz9VzZ3XrKktytC46Yb8j MULHANTbh42a46xNqr+iHtCuXLNkLeT21eouYuNglVOyTqOMLKSTbIEcjCSew8k/8qZrS3jLcjQ 06Vk8OEUz1EjeYghTp9XpVQbFOLGsWG2PoiVnna3PJkCXOp6Eff2DfEUqXaABkPIOhr89F8UK/i QhfZcD3m1ODsz3dPLnXWpQ7bNunmx6kUjrb+6lSiA5bTLOVnVIzqgu+TLrFCbsS3QfOi368IP9t WgcQr4dg8JdhIPJEHUyp+G1ZtSNloHzc/cBFJjAEaWDLS1RrQXPaOArIRVgCRouwi9a3BPIKEYl 173EZCisFTxJTq9ZjWA== X-Proofpoint-ORIG-GUID: qfqd89p5MndyiKCdse7hhzl37jK6gbcw X-Proofpoint-Spam-Info: AW1haW4tMjYwOTAzMDEyNyBTYWx0ZWRfX9ps/5MrBCaCn w61Laf3OaRQwcp9BnKrlQmP8ccMZHFB0FEdSs5UbRJFNgIvzoUKosSJyRrw9LAH6hmiH8M917vU e5vSkdu4x/dGDM/0eLXe8UkDiFE6KhM= X-Proofpoint-GUID: qfqd89p5MndyiKCdse7hhzl37jK6gbcw X-Authority-Analysis: v=2.4 cv=J4GaKgnS c=1 sm=1 tr=0 ts=6a9986f8 cx=c_pps a=P2rfLEam3zuxRRdjJWA2cw==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=DJpcGTmdVt4CTyJn9g5Z:22 a=z2R-DqfiRA8ArFDFZ6YA:9 a=QEXdDO2ut3YA:10 a=ODZdjJIeia2B_SHc_B0f:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-03_04,2026-09-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 bulkscore=0 suspectscore=0 phishscore=0 clxscore=1015 spamscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609030127 On 9/2/26 11:31 AM, Xilin Wu wrote: > On 9/2/2026 4:43 PM, Konrad Dybcio wrote: >> On 9/1/26 10:47 AM, Xilin Wu wrote: >>> The TC9563 PCI power-control driver powers off external downstream ports >>> whose device tree nodes have status = "disabled". >>> >>> On the Radxa Dragon Q8B, reading the Vendor ID from one of these >>> powered-off port functions during PCI enumeration raises an Arm SError >>> instead of returning an all-ones PCI error response. This prevents the >>> board from completing boot. >> >> I agree with the premise of the patch, but I'd like to understand why >> that happens - do you have any details? > > Unfortunately, I don't have further details. The downstream kernel also includes a similar workaround, so I suspect it's related to how the TC9563 chip is designed. I'm curious in why the port is still advertised on the bus if the i2c interface writes some magic bits to "disable" it on the IC side.. but perhaps that's just how that IC behaves and we can't do anything about it? Konrad