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Mon, 24 Aug 2026 00:17:11 -0700 (PDT) X-Received: by 2002:a05:6a00:a225:b0:847:8b11:5966 with SMTP id d2e1a72fcca58-851f9a8e890mr31621407b3a.1.1787555830650; Mon, 24 Aug 2026 00:17:10 -0700 (PDT) Received: from [10.218.35.45] ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc199e4b1e1sm719767a12.21.2026.08.24.00.17.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Aug 2026 00:17:10 -0700 (PDT) Message-ID: Date: Mon, 24 Aug 2026 12:47:05 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] PCI: qcom: Add register dump support for PCIe Link Down events To: Konrad Dybcio , Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org References: <20260811-regdump-v1-1-f22db3fb37c2@oss.qualcomm.com> Content-Language: en-US From: Krishna Chaitanya Chundru In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: FbBEWsk6c_ZuxOLzZ9eOIGEIKRaCzWRI X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI0MDA2MyBTYWx0ZWRfX1Kj3hQ8Z9IPQ z2VEe1mex5f8P9+4BEJJfvyERPeRHRoqiWW5rBf62aDkMhvjvwG7xOisN1T7J5jyVa2R8kRbtiU XTJkGPCzU+t30jiLHr7srfo6Snmca6/4jTQ7MYm59nndi4dgvNCSydTzpAY69Fv9v1tUkWI2lDZ LjZyHoqCntRTLgdNXt14sghji//SEkEph1679uMpafQMWIYQjsJ40NNcdbGSqagIFcx/jXv9CBo cLfA+Cl71guI5zs+WblBBodxme6UiEEXDrFjfDAwT9q2GYMVq3OIG40tHjSilKOSbfdR1vms/Vl FbhAEBC0/r8jefzVIGsOluGnplq+6bh1tBgpN2bWpwW01uerN512Qcdux0JjvRS5nla4J3GJoKc LwQ8j6gFkjcxGTFsVhNJI7ntNz5SDDOKhJ2GKliJlN/EDOVzn9BRURkfsqLesbmyHMCuK+1JZep mi8a6CIPAsYfz+0WLLw== X-Proofpoint-GUID: FbBEWsk6c_ZuxOLzZ9eOIGEIKRaCzWRI X-Proofpoint-Spam-Info: AW1haW4tMjYwODI0MDA2MyBTYWx0ZWRfXzUdCncobd0fV BlST/9zIla91/viGmywSpwZnoxnA1fuugKRENZqVH16VQ3mHiOrLsPR6ikFX5iv/Vf5i5l3Jeq/ GtkI94ZW9EmvEq8ajhmtGiNduzLr0T4= X-Authority-Analysis: v=2.4 cv=BNuDalQG c=1 sm=1 tr=0 ts=6a8beff8 cx=c_pps a=m5Vt/hrsBiPMCU0y4gIsQw==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=vLIU9tNIHzR1clMQrv8A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=IoOABgeZipijB_acs4fv: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=2026-08-24_02,2026-08-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 adultscore=0 malwarescore=0 clxscore=1015 bulkscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608240063 On 8/19/2026 4:15 PM, Konrad Dybcio wrote: > On 8/11/26 6:12 PM, Krishna Chaitanya Chundru wrote: >> When the PCIe link goes down unexpectedly, being able to inspect the >> state of key controller registers at the time of failure is valuable >> for root-causing the issue. > In this current form, does this patch not cause the splats to appear > for non-fatal linkdowns (e.g. hot-unplug)? I agree, but there is no way to differentiate, like link down is from the hot unplug or actual link down. For actual link down we can use it for debugging. >> If a storage endpoint is present downstream, the dump is printed >> directly via dev_err() so it is visible in dmesg immediately, since a >> devcoredump read from userspace could otherwise race with a storage >> failure. Otherwise, the buffer is handed to the devcoredump framework >> so it can be collected from /sys/class/devcoredump/ for offline >> analysis. > I think this is a bit too much, a single implementation is enough. we had a discussion with mani, mani doesn't want to dump these registers in dmesg, that is why we are using devcoredump. And in case of NVMe or storage devices and if the rootfs is in that storage, devcoredump may not work,  that is why we are dumping the regs in dmesg in case of storage devices. - Krishna Chaitanya. > > Konrad