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Tue, 05 May 2026 02:39:13 -0700 (PDT) X-Received: by 2002:a17:90b:4cc2:b0:35a:1762:92fc with SMTP id 98e67ed59e1d1-3650cefe95bmr13046918a91.26.1777973953118; Tue, 05 May 2026 02:39:13 -0700 (PDT) Received: from [10.92.176.206] ([202.46.23.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36528ad3154sm8656896a91.2.2026.05.05.02.39.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 May 2026 02:39:12 -0700 (PDT) Message-ID: Date: Tue, 5 May 2026 15:09:08 +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 1/2] thermal: qcom: tsens: atomic temperature read with hardware-guided retries To: Daniel Lezcano , Amit Kucheria , Thara Gopinath , "Rafael J . Wysocki" , Daniel Lezcano , Zhang Rui , Lukasz Luba Cc: linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, manaf.pallikunhi@oss.qualcomm.com References: <20260430054422.2461150-1-priyansh.jain@oss.qualcomm.com> <20260430054422.2461150-2-priyansh.jain@oss.qualcomm.com> <0d95cd5b-01a8-44b6-bd4c-a7e5fa81e181@oss.qualcomm.com> <1dd4746c-e93b-479f-8aed-ea9a21a03316@oss.qualcomm.com> Content-Language: en-US From: Priyansh Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: YbiL6WNyVJUBYyEXgzBBq2cNhu1x5Ece X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA1MDA4OSBTYWx0ZWRfXzBpTD7eFzqaG q7655Tc2q/53Co6PUH+UsVkZ3VZMHOUSQUsSgL6VAT5h1Ydq3wlLzHNT3TcCR5K6PYZk584ig6D XeD7WwSGGWZtIplt7DQ596/9CTZ7irqxs1XS5/59jm1PoEwZDXkK/wUYg0ppFy15ea+xvSsFEUM m6Fps5pILE3mcLolrQVlq26nP6tH1YvM48KlEgOKHqCTad/O5BquOsV5KCbIrivO8ah9AI0E1Vd CPZC/MU2PWMuKgelzTyEUtwjLJzuTbXgM+Ez6CLfc2581fp1yqPvOyHyVENGPGq/3zuNPIw8Sk1 D2/Pif2KCrAKMAyZDnmH/1mEnqESZ7Lnkqlm+oh5surKT0sp2lslDFEk1Jf3bKgNNM6jKRKrhuW 8e2CdUBCuvKzWJ8sDJRouBETMXtjnizVuIHquDyCGiDk3NjHMzYkrDcQajslIqcKHghxd2zs+BW Rhp459PEkpQURCTQG7Q== X-Authority-Analysis: v=2.4 cv=K+AS2SWI c=1 sm=1 tr=0 ts=69f9bac2 cx=c_pps a=UNFcQwm+pnOIJct1K4W+Mw==:117 a=j4ogTh8yFefVWWEFDRgCtg==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=c_rVVchIZH2FoSNRXpoA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=uKXjsCUrEbL0IQVhDsJ9:22 X-Proofpoint-GUID: YbiL6WNyVJUBYyEXgzBBq2cNhu1x5Ece 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=2026-05-05_02,2026-04-30_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 spamscore=0 adultscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605050089 On 05-05-2026 03:05 pm, Daniel Lezcano wrote: > On 5/5/26 10:48, Priyansh Jain wrote: > > [ ... ] > >>>>> >>>>> int prev = INTMAX; >>>>> >>>>> /* >>>>>   * An explanation ... >>>>>   */ >>>>> >>>>> for (i = 0; i < max_retry; i++) { >>>>> >>>>>      int value, valid; >>>>> >>>>>      ret = regmap_field_read(priv->rf[field], &status); >>>>>      if (ret) >>>>>          return ret; >>>>> >>>>>      value = FIELD_GET(priv->feat->last_temp_mask, status); >>>>> >>>>>      valid = FIELD_GET(priv->feat->valid_bit, status) >>>>>      if (valid) >>>>>          return value; >>>>> >>>>>      if (value == prev) >>>>>          return value; >>>>> >>>>>      prev = value; >>>>> } >>>>> >>>>> return -EAGAIN; >>>>> >>>>> (Not tested) >>>> This approach has some misalignment with the HW recommendations. >>>> As per the HW guidelines, 3 back‑to‑back reads must be performed >>>> until a valid read is observed. >>>> b or c should be returned only if none of the three reads(a,b,c) >>>> report the valid bit not set. >>> >>> Right I missed the point the HW recommendations is to read 3 times in >>> any case. Maybe replace if (value == prev) continue; ? >>> >> We need to store all three readings because, if all of them are >> invalid, we must compare the first, second, and third reads using the >> following logic: >> >> if a == b, return b >> else if b == c, return c >> else return -EAGAIN >> >> Given this requirement, comparing (value == prev) inside the read loop >> would not be correct, as it does not preserve all three samples for >> the final comparison. > > I tried the different combinations and comparing inside the loop should > work. But the optimization introduces an implicit inference not helping > for the clarity of the code and probably prone to errors in case of > changes. So probably simpler to keep your approach. Please add a comment > above the if a == b return b else ... > > Thanks Thanks , will go ahead with my approach and will add a comment before comparison code . Thanks, Priyansh > >   -- Daniel