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Thu, 22 Oct 2026 09:58:48 -0700 (PDT) Received: from [192.168.1.9] ([106.222.235.141]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ada48876ebsm5013445a91.1.2026.10.22.09.58.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Oct 2026 09:58:47 -0700 (PDT) Message-ID: Date: Thu, 22 Oct 2026 22:28:42 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: dts: qcom: shikra: Drop CPU critical trips To: Abel Vesa Cc: Konrad Dybcio , Bjorn Andersson , Konrad Dybcio , Abel Vesa , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260924-shikra_crit_trip-v1-1-730c48fa998e@oss.qualcomm.com> <53c6b966-a6ff-4b91-a2b7-d7faee5a6605@oss.qualcomm.com> <3a87d077-8b8b-4bcb-9f5a-03920ef3d38b@oss.qualcomm.com> <727ru4mlgn2bf7ta42ww7772mekk6bea7sni5b2h556pk3c6xw@4atjqo2ygylo> <194cdf44-059d-4d03-8cef-d674ba37006b@oss.qualcomm.com> Content-Language: en-US From: Gaurav Kohli In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: -GG6GgkAF9KCXp8XSdvsMcFZH_rQCAGR X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIyMDA2NyBTYWx0ZWRfX9ec5XfdFvkJB 6hWh4bj16ZL+nzGX3Cdz5sZzGV/mmGbXjzZ3JOlMnPT/SP8qaAACtPlJ98g6Gs+RhYIBxJvJdRG JRa9xG2I4MMgJdZiJMcvJ3s45K/BNHy4H7PbAGKST+Fbu6TagQgcORU9zOBU9bnbA9TRrhRYxrQ CzSjvvNoxHsvUyNG30iB+HLvuhIHWcauldso8L5NpW1dAnZ3z2W3tam1FR/7jtP41XA1TVB1Ivu ohkPpNluhBKT3Dt8YunVsqun1OSX9kSu5pcWXGCfC85fpGdqt/krYHlVOb833OF3imb6adWbNsv DNvmigkXZn55SIxVo9wx3EAzMa+nVjxx4ZBJlRPUmfWb/8kpIsA9fv7mEibxyDxExN/6Ecs7Htp jogkEVYWF7JT1QLhTiTwTiQt3s4D2pPKQ3w8kNmoQkWLacRB3oTO+wqmLM5iiCLCXGc+8TrWugh 12qQj0C+5DXWtsFQFzg== X-Proofpoint-GUID: -GG6GgkAF9KCXp8XSdvsMcFZH_rQCAGR X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIyMDA2NyBTYWx0ZWRfX0jxAwSzjofKy gxcmJiFVrLBuSspkl+pGKZMn0p9d4l7hbbRjUdrFg5i6bO8zd2tuJaXE9HuaucDrMALXf5GA0++ 2Cylb6iA7G54zCRd2rBscl+3cTbrFkM= X-Authority-Analysis: v=2.4 cv=UaHE26SN c=1 sm=1 tr=0 ts=6ada40ca cx=c_pps a=vVfyC5vLCtgYJKYeQD43oA==:117 a=8wa5AUNoahJ04lRaSfAPWg==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=NRCdo2LqAGfow365lYEA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=rl5im9kqc5Lf4LNbBjHf:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-22_05,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 spamscore=0 malwarescore=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610220067 On 10/21/2026 5:36 PM, Abel Vesa wrote: > On 26-10-21 17:12:11, Gaurav Kohli wrote: >> >> >> On 10/20/2026 6:26 PM, Abel Vesa wrote: >>> On 26-10-19 20:03:47, Gaurav Kohli wrote: >>>> >>>> >>>> On 10/15/2026 4:43 PM, Konrad Dybcio wrote: >>>>> On 9/25/26 12:24 PM, Gaurav Kohli wrote: >>>>>> >>>>>> >>>>>> On 9/25/2026 3:13 PM, Abel Vesa wrote: >>>>>>> On 26-09-24 19:52:32, Gaurav Kohli wrote: >>>>>>>> Shikra firmware handles CPU thermal mitigation up to 117 C, while >>>>>>>> Linux CPU critical trips trigger at 115 C. This can shut the system >>>>>>>> down before firmware reaches the end of its mitigation range. >>>>>>>> >>>>>>>> Drop the critical trips from the CPU thermal zones and leave the hot >>>>>>>> trips, non-CPU critical trips and GPUSS passive cooling map unchanged. >>>>>>> >>>>>>> I thought that was the whole point of having the critical trips set to >>>>>>> 115 C, so that the kernel can gracefully shut down before firmware cuts >>>>>>> it off. >>>>>>> >>>>>>> What happens if CPU gets to 117 C and the critical trips are removed? >>>>>>> How will firmware thermal mitigation handle it? >>>>>> >>>>>> Thanks Abel for review. >>>>>> >>>>>> For the CPU thermal zones on this SoC, hardware-side mitigation is already available at 115 C and 117 C, and hardware shutdown is at 120 C. Because of that, a Linux critical trip at 115 C is not very useful. It overlaps with the hardware mitigation range and can trigger shutdown before the firmware thermal sequence has completed. >>>>> >>>>> Does the hardware mitigation just pull the plug, or does it signal >>>>> to the OS that it's about to? We absolutely need the OS to be aware, >>>>> so that e.g. the filesystem will be synced. >>>> >>>> Thanks Konrad for the review. >>>> >>>> The OS is not notified before the final HW shutdown at 120 C. There is also >>>> no useful margin for a Linux critical trip here, firmware/HW mitigation >>>> starts at 115/117 C and hw shutdown is at 120. >>>> >>>> So 115 C overlaps with firmware mitigation, while placing it higher is >>>> too close to HW shutdown to be useful. >>> >>> But having the 115 C one will allow the kernel to take all the necessary >>> steps to bring the system down gracefully, while relying solely on the >>> firmware will just kill the system before kernel can do anything. >> >> Thanks Abel for the review. >> >> On this target, 115/117 C firmware mitigation is throttling/prevention, not >> shutdown. The final HW shutdown threshold is 120 C. >> >> The 115 C Linux critical trip therefore starts shutdown exactly when >> firmware mitigation begins. Moving it higher also leaves too little margin >> before 120 C. >> >> So this patch drops only the CPU critical trips. Would you prefer keeping a >> Linux critical trip at 118 C ? > > Yes. Again, we don't want the firmware to crash the system before kernel > has a chance to bring it down gracefully. Sure, will add at 118. > > But how does the firmware mitigation (throttling/prevention) is done? > Shouldn't kernel be aware of such thing ? LMH hardware handles the CPU frequency throttling. The kernel is aware of LMH events through the cpufreq driver’s interrupt/polling path. thanks Gaurav