On Mon, Dec 16, 2024 at 08:36:46PM +0300, Murad Masimov wrote:
> The values returned by the driver after processing the contents of the
> Shunt Voltage Register and the Shunt Limit Registers do not correspond to the
> 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, the
> result is incorrect. Moreover, the PGA shift calculated with the
> tmp51x_get_pga_shift function is relevant only to the Shunt Voltage Register,
> 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 setting.
> 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 = 8, and regval = 1000 0011 0000 0000, then the decimal value must
> be -32000, but the value calculated by the driver will be 33536.
>
> * Shunt Limit Register
> If regval = 1000 0011 0000 0000, then the decimal value must be -32000, but
> the value calculated by the driver will be 768, if PGA = 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 sensor chips.")
> Signed-off-by: Murad Masimov <m.masimov@xxxxxxxxx>
Applied, after fixing checkpatch complaints.
Guenter
