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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b083527f84sm17441355ad.18.2026.03.20.03.02.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Mar 2026 03:02:05 -0700 (PDT) Message-ID: <4c75f644-2c06-48b1-a72b-1b84be7ba4ab@oss.qualcomm.com> Date: Fri, 20 Mar 2026 18:02:00 +0800 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] cpufreq: conservative: Reset requested_freq on limits change To: Viresh Kumar , "Rafael J. Wysocki" Cc: linux-pm@vger.kernel.org, Vincent Guittot , Sumit Semwal , Lifeng Zheng , linux-kernel@vger.kernel.org, zhongqiu.han@oss.qualcomm.com References: Content-Language: en-US From: Zhongqiu Han In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzIwMDA3NyBTYWx0ZWRfX+bOjs6Sa3S0k otfhujDxQ3zpZa3wl7GpHaJUtJqClO0nQzK9boWrZcoDSCtCWSkmybxxQxGvm83mXIe00/ZgT3d sWNGGaeZQIHrDRhfzxmB4cGFGxDg9uVct+k1gGjb8/U7c2Fq9AfE0CbQn7kk5t8jUYfWsVszW0i AHt8uBkOzkxZiwlXppWTyY0Vc+FP1Wo3cZVL0l8PRMb1hki7Yuqfil6k+dKOcRe9DJQde/H4B0u R6zXOcNU6y74RqmOOLvTFo/8BYJzqHZZ9pYFSxyD1wiLAO9Jze11KiF78/2RwBMvoRLx1THu4UA rdzC7LmcP1ekHVCFBPF6hfUZ7XLenzLPFuLUG7G5VUIXR3Q5Riph43ji//NGTzaiAJhgxHKdXm6 +fZq56BdJbxmZmHe8PIMkIUF1OGusB12mZyFnUZvBT4OvbktKkzfcqsbX2vxadrH/+2P+b/HHeM Sj1hvTz45iEugQQkCTg== X-Proofpoint-GUID: EVubm5Tuxhn6FU7Y-nJR6cOwS2l5hmQ6 X-Proofpoint-ORIG-GUID: EVubm5Tuxhn6FU7Y-nJR6cOwS2l5hmQ6 X-Authority-Analysis: v=2.4 cv=Y/D1cxeN c=1 sm=1 tr=0 ts=69bd1b1e cx=c_pps a=MTSHoo12Qbhz2p7MsH1ifg==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=VwQbUJbxAAAA:8 a=i0EeH86SAAAA:8 a=EUspDBNiAAAA:8 a=KKAkSRfTAAAA:8 a=tFKV1D7yu5sg3FCBrf4A:9 a=QEXdDO2ut3YA:10 a=GvdueXVYPmCkWapjIL-Q:22 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-20_01,2026-03-19_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 phishscore=0 bulkscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603200077 On 3/20/2026 5:38 PM, Viresh Kumar wrote: > A recently reported issue highlighted that the cached requested_freq > is not guaranteed to stay in sync with policy->cur. If the platform > changes the actual CPU frequency after the governor sets one (e.g. > due to platform-specific frequency scaling) and a re-sync occurs > later, policy->cur may diverge from requested_freq. > > This can lead to incorrect behavior in the conservative governor. > For example, the governor may assume the CPU is already running at > the maximum frequency and skip further increases even though there > is still headroom. > > Avoid this by resetting the cached requested_freq to policy->cur on > detecting a change in policy limits. > Reviewed-by: Zhongqiu Han > Reported-by: Lifeng Zheng > Tested-by: Lifeng Zheng > Link: https://lore.kernel.org/all/20260210115458.3493646-1-zhenglifeng1@huawei.com/ > Signed-off-by: Viresh Kumar > --- > [v2] > - Completely different design to solve the problem. > > drivers/cpufreq/cpufreq_conservative.c | 12 ++++++++++++ > drivers/cpufreq/cpufreq_governor.c | 3 +++ > drivers/cpufreq/cpufreq_governor.h | 1 + > 3 files changed, 16 insertions(+) > > diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c > index e0e847764511..df01d33993d8 100644 > --- a/drivers/cpufreq/cpufreq_conservative.c > +++ b/drivers/cpufreq/cpufreq_conservative.c > @@ -313,6 +313,17 @@ static void cs_start(struct cpufreq_policy *policy) > dbs_info->requested_freq = policy->cur; > } > > +static void cs_limits(struct cpufreq_policy *policy) > +{ > + struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data); > + > + /* > + * The limits have changed, so may have the current frequency. Reset > + * requested_freq to avoid any unintended outcomes due to the mismatch. > + */ > + dbs_info->requested_freq = policy->cur; > +} > + > static struct dbs_governor cs_governor = { > .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"), > .kobj_type = { .default_groups = cs_groups }, > @@ -322,6 +333,7 @@ static struct dbs_governor cs_governor = { > .init = cs_init, > .exit = cs_exit, > .start = cs_start, > + .limits = cs_limits, > }; > > #define CPU_FREQ_GOV_CONSERVATIVE (cs_governor.gov) > diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c > index 36eb7aee4bcd..acf101878733 100644 > --- a/drivers/cpufreq/cpufreq_governor.c > +++ b/drivers/cpufreq/cpufreq_governor.c > @@ -563,6 +563,7 @@ EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop); > > void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy) > { > + struct dbs_governor *gov = dbs_governor_of(policy); > struct policy_dbs_info *policy_dbs; > > /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */ > @@ -574,6 +575,8 @@ void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy) > mutex_lock(&policy_dbs->update_mutex); > cpufreq_policy_apply_limits(policy); > gov_update_sample_delay(policy_dbs, 0); > + if (gov->limits) > + gov->limits(policy); > mutex_unlock(&policy_dbs->update_mutex); > > out: > diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h > index 168c23fd7fca..1462d59277bd 100644 > --- a/drivers/cpufreq/cpufreq_governor.h > +++ b/drivers/cpufreq/cpufreq_governor.h > @@ -138,6 +138,7 @@ struct dbs_governor { > int (*init)(struct dbs_data *dbs_data); > void (*exit)(struct dbs_data *dbs_data); > void (*start)(struct cpufreq_policy *policy); > + void (*limits)(struct cpufreq_policy *policy); > }; > > static inline struct dbs_governor *dbs_governor_of(struct cpufreq_policy *policy) -- Thx and BRs, Zhongqiu Han