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Mon, 21 Sep 2026 04:44:54 -0700 (PDT) X-Received: by 2002:ad4:5ca8:0:b0:912:127c:d7f6 with SMTP id 6a1803df08f44-913fc9782acmr1419036d6.4.1789991093948; Mon, 21 Sep 2026 04:44:53 -0700 (PDT) Received: from [192.168.202.12] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6aa67e35d64sm4266508a12.30.2026.09.21.04.44.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Sep 2026 04:44:52 -0700 (PDT) Message-ID: <15daa9f3-162c-43fd-b22e-0194b82f602c@oss.qualcomm.com> Date: Mon, 21 Sep 2026 13:44:50 +0200 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 0/8] arm64: dts: qcom: Add t-power-on-us property for PCIe root ports To: Manivannan Sadhasivam , Krishna Chaitanya Chundru 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 References: <20260911-t_pwr_on-v1-0-c9eee197d082@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-GUID: nG2drxvJNHi1orjENa5C89awDzXyQWPP X-Authority-Analysis: v=2.4 cv=dPczC+Zb c=1 sm=1 tr=0 ts=6ab118b6 cx=c_pps a=oc9J++0uMp73DTRD5QyR2A==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=Ei8_fX62Guvo6lbYW7UA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=iYH6xdkBrDN1Jqds4HTS:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIxMDE3MCBTYWx0ZWRfXw/fD0pwBQ9Yv UHGGxCerNyozfjqOmpeBZenaD+J7H5c7cmFDCly2Q8+YPUlSa5n3I7pm6lAX4s0/PVeNnawu8L1 gs8MQlP0YvFARCKFUazPZVnUW2tLXKMjOqyIpInwPS1LIrF7qnLiuam/E1tn/y3Z5g8O3+t2zg6 XcsoIw3XWVK1OG4Ge72xHqWg+41Uk0i3pZO4J4Cpv1KVzH1vKwE7h7zAZAIPFT/bVDlRYsRcfM/ FNKrQzBOlZCQNStUC737AHXoN0Kb1aTb0usQDcWtw6H3tyRvzYMgzEzyxb+kEl/oC0NSKfKp93G MMl0jF6W7VsRKT9Cy7tS2HZviZZjuY+1tKIAlBUa1JDQ829rwd56Xb6XaerCZKBstvG920BWhdV qBkf1SSosr0Gar9q1q7quFAdtnl5toAd6qB7l+3lSHbfCqPwbVe76U3g8TTSrKgzKprlZ16PucO T5svGkjevD8LFYsC0Yw== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIxMDE3MCBTYWx0ZWRfX27cbewTJh9Hg krnFvNBXjjsu/eOrjG3ZLWGY1WYdFpAibR/3GqMduy3U09kJN9yNtuFWkcd1RwlJ1RjkBkGzggb gVpbpBUz7HFJKgsMoFobRwYBQDS+gTw= X-Proofpoint-ORIG-GUID: nG2drxvJNHi1orjENa5C89awDzXyQWPP 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=2026-09-21_04,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 adultscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609210170 On 9/21/26 1:34 PM, Manivannan Sadhasivam wrote: > On Mon, Sep 21, 2026 at 04:40:43PM +0530, Krishna Chaitanya Chundru wrote: >> >> >> On 9/21/2026 2:09 PM, Konrad Dybcio wrote: >>> On 9/11/26 8:50 AM, Krishna Chaitanya Chundru wrote: >>>> The Qualcomm PCIe host controller driver added support for parsing the >>>> -power-on-us property[1] from each Root Port node and programming it as >>>> art of host initialization (PCI: qcom: Program T_POWER_ON) [2]. Prior to >>>> this, T_POWER_ON was expected to be programmed correctly in hardware or >>>> by the bootloader, but not all targets support this, which can lead to an >>>> incorrectly calculated LTR_L1.2_THRESHOLD in aspm.c and improper L1.2 exit >>>> behavior. >>> This is a good problem description. Does it have observable effects >>> that could also be mentioned here, beyond perhaps lspci reporting >>> an odd value? >> we haven't seen direct problem till now, but we might seen some issue due to >> incorrect LTR_L1.2_THRESHOLD value. > > Can you specify what issue can be seen without this series? I'd assume the > link will fail to enter L1.2 and will result in slightly more power drain as > the link can only enter L1.1. Would that produce an explicit warning message somewhere? i.e. can I reasonably be able to tell I'm missing this change and I need it? (if not, this is of course not a blocker, but the answer to that question is always worth sharing) Konrad