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Mon, 16 Dec 2024 20:37:16 +0300 (MSK) Received: from GS-NOTE-190.mt.ru (10.0.246.113) by mmail-p-exch02.mt.ru (81.200.124.62) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.1544.4; Mon, 16 Dec 2024 20:37:13 +0300 From: Murad Masimov To: Eric Tremblay CC: Jean Delvare , Guenter Roeck , , , , Murad Masimov Subject: [PATCH 1/3] hwmon: (tmp513) Fix interpretation of values of Shunt Voltage and Limit Registers Date: Mon, 16 Dec 2024 20:36:46 +0300 Message-ID: <20241216173648.526-2-m.masimov@maxima.ru> X-Mailer: git-send-email 2.46.0.windows.1 In-Reply-To: <20241216173648.526-1-m.masimov@maxima.ru> References: <20241216173648.526-1-m.masimov@maxima.ru> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: mt-exch-01.mt.ru (91.220.120.210) To mmail-p-exch02.mt.ru (81.200.124.62) X-KSMG-Rule-ID: 7 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Lua-Profiles: 189867 [Dec 16 2024] X-KSMG-AntiSpam-Version: 6.1.1.7 X-KSMG-AntiSpam-Envelope-From: m.masimov@mt-integration.ru X-KSMG-AntiSpam-Rate: 0 X-KSMG-AntiSpam-Status: not_detected X-KSMG-AntiSpam-Method: none X-KSMG-AntiSpam-Auth: dmarc=none header.from=maxima.ru;spf=none smtp.mailfrom=mt-integration.ru;dkim=none X-KSMG-AntiSpam-Info: LuaCore: 47 0.3.47 57010b355d009055a5b6c34e0385c69b21a4e07f, {rep_avail}, {Tracking_smtp_not_equal_from}, {Tracking_from_domain_doesnt_match_to}, 81.200.124.62:7.1.2;mt-integration.ru:7.1.1;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;127.0.0.199:7.1.2;ksmg02.maxima.ru:7.1.1;maxima.ru:7.1.1, {Tracking_smtp_domain_mismatch}, {Tracking_smtp_domain_2level_mismatch}, FromAlignment: n, ApMailHostAddress: 81.200.124.62 X-MS-Exchange-Organization-SCL: -1 X-KSMG-AntiSpam-Interceptor-Info: scan successful X-KSMG-AntiPhishing: Clean X-KSMG-LinksScanning: Clean X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 2.0.1.6960, bases: 2024/12/16 14:34:00 #26899616 X-KSMG-AntiVirus-Status: Clean, skipped Content-Type: text/plain; charset="utf-8" The values returned by the driver after processing the contents of the Shunt Voltage Register and the Shunt Limit Registers do not correspond to t= he TMP512/TMP513 specifications. A raw register value is converted to a signed integer value by a sign extension in accordance with the algorithm provided= in the specification, but due to the off-by-one error in the sign bit index, t= he result is incorrect. Moreover, the PGA shift calculated with the tmp51x_get_pga_shift function is relevant only to the Shunt Voltage Registe= r, but is also applied to the Shunt Limit Registers. According to the TMP512 and TMP513 datasheets, the Shunt Voltage Register (= 04h) is 13 to 16 bit two's complement integer value, depending on the PGA settin= g. The Shunt Positive (0Ch) and Negative (0Dh) Limit Registers are 16-bit two's complement integer values. Below are some examples: * Shunt Voltage Register If PGA =3D 8, and regval =3D 1000 0011 0000 0000, then the decimal value mu= st be -32000, but the value calculated by the driver will be 33536. * Shunt Limit Register If regval =3D 1000 0011 0000 0000, then the decimal value must be -32000, b= ut the value calculated by the driver will be 768, if PGA =3D 1. Fix sign bit index, and also correct misleading comment describing the tmp51x_get_pga_shift function. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 59dfa75e5d82 ("hwmon: Add driver for Texas Instruments TMP512/513 se= nsor chips.") Signed-off-by: Murad Masimov --- drivers/hwmon/tmp513.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/tmp513.c b/drivers/hwmon/tmp513.c index 926d28cd3fab..d401cb55de14 100644 --- a/drivers/hwmon/tmp513.c +++ b/drivers/hwmon/tmp513.c @@ -182,7 +182,7 @@ struct tmp51x_data { struct regmap *regmap; }; -// Set the shift based on the gain 8=3D4, 4=3D3, 2=3D2, 1=3D1 +// Set the shift based on the gain: 8 -> 1, 4 -> 2, 2 -> 3, 1 -> 4 static inline u8 tmp51x_get_pga_shift(struct tmp51x_data *data) { return 5 - ffs(data->pga_gain); @@ -204,7 +204,9 @@ static int tmp51x_get_value(struct tmp51x_data *data, u= 8 reg, u8 pos, * 2's complement number shifted by one to four depending * on the pga gain setting. 1lsb =3D 10uV */ - *val =3D sign_extend32(regval, 17 - tmp51x_get_pga_shift(data)); + *val =3D sign_extend32(regval, + reg =3D=3D TMP51X_SHUNT_CURRENT_RESULT ? + 16 - tmp51x_get_pga_shift(data) : 15); *val =3D DIV_ROUND_CLOSEST(*val * 10 * MILLI, data->shunt_uohms); break; case TMP51X_BUS_VOLTAGE_RESULT: -- 2.39.2