Unverified Commit c7ecb6a6 authored by James Calligeros's avatar James Calligeros Committed by Mark Brown
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ASoC: tas2770: Fix order of operations for temperature calculation 



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: ff73e278 ("ASoC: tas2770: expose die temp to hwmon")
Signed-off-by: default avatarJames Calligeros <jcalligeros99@gmail.com>
Link: https://patch.msgid.link/20260425-tas27xx-hwmon-fixes-v1-3-83c13b8e8f54@gmail.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 4cfb5971

sound/soc/codecs/tas2770.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}