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Wed, 14 Oct 2026 09:14:48 -0700 (PDT) X-Received: by 2002:a05:620a:439e:b0:93e:54fc:2c79 with SMTP id af79cd13be357-93ebd264008mr2745441985a.5.1791994488098; Wed, 14 Oct 2026 09:14:48 -0700 (PDT) Received: from [192.168.226.26] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c3eda043cbfsm2141866b.55.2026.10.14.09.14.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Oct 2026 09:14:47 -0700 (PDT) Message-ID: <3d8158f1-8c26-4866-a318-abaad47f75ac@oss.qualcomm.com> Date: Wed, 14 Oct 2026 18:14:43 +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 RFC 03/16] OPP: Retry failed default single-clock transitions To: Dmitry Baryshkov , Konrad Dybcio Cc: Stephen Boyd , Brian Masney , Jerome Brunet , Viresh Kumar , Nishanth Menon , "Rafael J. Wysocki" , Pavel Machek , Len Brown , Greg Kroah-Hartman , Danilo Krummrich , Johan Hovold , Ulf Hansson , Bjorn Andersson , Abel Vesa , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Neil Armstrong , Mike Tipton , Taniya Das , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, driver-core@lists.linux.dev, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org References: <20261014-topic-qc_clk_dvfs-v1-0-3041b788e9f7@oss.qualcomm.com> <20261014-topic-qc_clk_dvfs-v1-3-3041b788e9f7@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: AW1haW4tMjYxMDE0MDA2NCBTYWx0ZWRfXx3fbp03FZcTo okWUOLWEKE9FU9E1Ki3FvM+du4NHhJuZmBu2ZEnbbcb6BzCT3od+rfShKUws6OAEU4SA5MzACOe sznNWU5OoOMFB21sFeXTX3xxT+icET67Y7dZMOb2c/yjdEmIojcAa7OEKVeoyMIkcUzduScPaDs Ma0vJZ0kd0ApPAKPjOloyFO/F/8s2micL3l7M3H5d9Ebg609yMgmx53nqV09Dzi9b7DDqriE3lB aO3FjhiFyKowl+MEsvXY/Sz8ANcdf5aeelczhujPhccr7wkSYBHk7KYL20qYLZTrTmllMUwnT7M 3WcgRM0038qkONZ6t71yxo1DNOiZ+22AdBCMEgQ9awOJcBXk4XkLq64yVTUJ1qYb6UusnUh8Ur+ Mpo+f45JBQJB1W78VXs7QhqbBFEpNcX35IayCnBBGopZNfzIQoBM15hZjmPDor34460yZ4NMyZm axU2EJo7k78pF85XJkQ== X-Proofpoint-GUID: Yg2_mgdyG9X4md75P-aEiPIDkMGpBGk5 X-Authority-Analysis: v=2.4 cv=P6avFSAu c=1 sm=1 tr=0 ts=6acfaa79 cx=c_pps a=oc9J++0uMp73DTRD5QyR2A==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=EUspDBNiAAAA:8 a=tSyx0q1tghd3iirTVWYA:9 a=QEXdDO2ut3YA:10 a=iYH6xdkBrDN1Jqds4HTS:22 X-Proofpoint-ORIG-GUID: Yg2_mgdyG9X4md75P-aEiPIDkMGpBGk5 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDE0MDA2NCBTYWx0ZWRfXwTwia4qN3/Zp kLb/QQscCHKmIi2fI5x6yHsN3UnTNVd5FyIMHWK1iHHJvJU6iTafVWWiXjNdnVhSgH3GKQGAwei lz6bTMUeKKzN5w3GtU5J9Zr7go6q6G0= 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=2026-10-13_01,2026-10-14_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 suspectscore=0 clxscore=1015 impostorscore=0 malwarescore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610140064 On 10/14/26 3:35 PM, Dmitry Baryshkov wrote: > On Wed, Oct 14, 2026 at 02:19:03PM +0200, Konrad Dybcio wrote: >> From: Konrad Dybcio >> >> A failed OPP transition need not leave the clock at the last successful >> OPP's frequency. If hardware changed before the error, the default >> single-clock path can subsequently skip a necessary retry because its > > What is a necessary retry? Shouldn't it be: try, rollback if it fails? The failure scenario is: opp-table { opp-400000000 { // low }; opp-1000000000 { // high }; }'; 1. The device is running at Low. OPP caches 400 MHz and the Low OPP. 2. A driver requests High. - OPP raises the voltage to 0.95 V. - clk_set_rate(..., 1 GHz) changes the clock, but returns an error - Assume clk_get_rate() can report the resulting 1 GHz rate. 3. The transition returns an error, so current_opp still points to Low. 4. The caller tries to recover by requesting Low again. Perhaps I should have included that in the commit message. Konrad