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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82739d4d826sm13646384b3a.10.2026.03.02.07.50.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Mar 2026 07:50:27 -0800 (PST) Sender: Guenter Roeck Message-ID: <58c0e46e-fa58-40ba-91f0-235a4cef034c@roeck-us.net> Date: Mon, 2 Mar 2026 07:50:24 -0800 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] (ina2xx) Drop bus_voltage_shift configuration To: Jonas Rebmann Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, Ian Ray References: <20260302-ina2xx-shift-v1-1-4ff5b7b76d51@pengutronix.de> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: <20260302-ina2xx-shift-v1-1-4ff5b7b76d51@pengutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi, On 3/2/26 07:26, Jonas Rebmann wrote: > The INA219 has the lowest three bits of the bus voltage register > zero-reserved and the bus_voltage_shift ina2xx_config field was > introduced to accommodate for that. > > The INA234 has four bits of the bus voltage, of the shunt voltage, and > of the current registers zero-reserved but the latter two were > implemented by choosing a 16x higher conversion constant instead of a > separate field specifying a bit shift. > > For consistency and simplicity, drop bus_voltage_shift and adapt the > conversion constants for INA219 and INA234 accordingly, yielding the > same measurement values. > This isn't about simplicity, it is about correctness. The datasheet for INA234 says for the lower 4 bits: Always returns 0. Remove these bits from the full result by doing a right arithmetic shift which is what we should do for all chips with reserved bits instead of assuming that the reserved bits always return 0. Thanks, Guenter > Signed-off-by: Jonas Rebmann > --- > drivers/hwmon/ina2xx.c | 15 ++++----------- > 1 file changed, 4 insertions(+), 11 deletions(-) > > diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c > index 836e15a5a780..d7c894d7353c 100644 > --- a/drivers/hwmon/ina2xx.c > +++ b/drivers/hwmon/ina2xx.c > @@ -151,7 +151,6 @@ struct ina2xx_config { > bool has_update_interval; > int calibration_value; > int shunt_div; > - int bus_voltage_shift; > int bus_voltage_lsb; /* uV */ > int power_lsb_factor; > }; > @@ -172,8 +171,7 @@ static const struct ina2xx_config ina2xx_config[] = { > .config_default = INA219_CONFIG_DEFAULT, > .calibration_value = 4096, > .shunt_div = 100, > - .bus_voltage_shift = 3, > - .bus_voltage_lsb = 4000, > + .bus_voltage_lsb = 500, > .power_lsb_factor = 20, > .has_alerts = false, > .has_ishunt = false, > @@ -184,7 +182,6 @@ static const struct ina2xx_config ina2xx_config[] = { > .config_default = INA226_CONFIG_DEFAULT, > .calibration_value = 2048, > .shunt_div = 400, > - .bus_voltage_shift = 0, > .bus_voltage_lsb = 1250, > .power_lsb_factor = 25, > .has_alerts = true, > @@ -196,8 +193,7 @@ static const struct ina2xx_config ina2xx_config[] = { > .config_default = INA226_CONFIG_DEFAULT, > .calibration_value = 2048, > .shunt_div = 400, /* 2.5 µV/LSB raw ADC reading from INA2XX_SHUNT_VOLTAGE */ > - .bus_voltage_shift = 4, > - .bus_voltage_lsb = 25600, > + .bus_voltage_lsb = 1600, > .power_lsb_factor = 32, > .has_alerts = true, > .has_ishunt = false, > @@ -207,7 +203,6 @@ static const struct ina2xx_config ina2xx_config[] = { > [ina260] = { > .config_default = INA260_CONFIG_DEFAULT, > .shunt_div = 400, > - .bus_voltage_shift = 0, > .bus_voltage_lsb = 1250, > .power_lsb_factor = 8, > .has_alerts = true, > @@ -219,7 +214,6 @@ static const struct ina2xx_config ina2xx_config[] = { > .config_default = SY24655_CONFIG_DEFAULT, > .calibration_value = 4096, > .shunt_div = 400, > - .bus_voltage_shift = 0, > .bus_voltage_lsb = 1250, > .power_lsb_factor = 25, > .has_alerts = true, > @@ -281,8 +275,7 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg, > val = DIV_ROUND_CLOSEST((s16)regval, data->config->shunt_div); > break; > case INA2XX_BUS_VOLTAGE: > - val = (regval >> data->config->bus_voltage_shift) * > - data->config->bus_voltage_lsb; > + val = regval * data->config->bus_voltage_lsb; > val = DIV_ROUND_CLOSEST(val, 1000); > break; > case INA2XX_POWER: > @@ -387,7 +380,7 @@ static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, long val) > return clamp_val(val, 0, SHRT_MAX); > case INA2XX_BUS_VOLTAGE: > val = clamp_val(val, 0, 200000); > - val = (val * 1000) << data->config->bus_voltage_shift; > + val = val * 1000; > val = DIV_ROUND_CLOSEST(val, data->config->bus_voltage_lsb); > return clamp_val(val, 0, USHRT_MAX); > case INA2XX_POWER: > > --- > base-commit: f08c5de5f61a117ba5326d3d5b86e884077da2d0 > change-id: 20260302-ina2xx-shift-89ed2c5d2e72 > > Best regards, > -- > Jonas Rebmann >