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ASoC: tas2770: Fix order of operations for temperature calculation

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The order of operations to derive the temperature from the temp
register values was wrong, since 1000 / 16 is not an integer. This
resulted in the calculated temperature value deviating from the
value represented by the registers slightly, which was most obvious
when the registers were zeroed (-92.265 *C vs the expected -93.000 *C).

Scale the reading before dividing the whole thing by 16 to correct
this.

Fixes: ff73e27801 ("ASoC: tas2770: expose die temp to hwmon")
Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
Link: https://patch.msgid.link/20260425-tas27xx-hwmon-fixes-v1-3-83c13b8e8f54@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
James Calligeros
2026-04-25 10:44:05 +10:00
committed by Mark Brown
parent 4cfb5971c2
commit c7ecb6a619
1 changed files with 2 additions and 2 deletions
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4
sound/soc/codecs/tas2770.c
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@@ -624,7 +624,7 @@ static int tas2770_read_die_temp(struct tas2770_priv *tas2770, long *result)
/*
* As per datasheet: divide register by 16 and subtract 93 to get
* degrees Celsius. hwmon requires millidegrees. Let's avoid rounding
* errors by subtracting 93 * 16 then multiplying by 1000 / 16.
* errors by subtracting 93 * 16 and scaling before dividing.
*
* NOTE: The ADC registers are initialised to 0 on reset. This means
* that the temperature will read -93 *C until the chip is brought out
@@ -633,7 +633,7 @@ static int tas2770_read_die_temp(struct tas2770_priv *tas2770, long *result)
* value read back from its registers will be the last value sampled
* before entering software shutdown.
*/
*result = (reading - (93 * 16)) * (1000 / 16);
*result = (reading - (93 * 16)) * 1000 / 16;
return 0;
}