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hwmon: (adt7475) Make volt2reg return same reg as reg2volt input

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reg2volt returns the voltage that matches a given register value.
Converting this back the other way with volt2reg didn't return the same
register value because it used truncation instead of rounding.

This meant that values read from sysfs could not be written back to sysfs
to set back the same register value.

With this change, volt2reg will return the same value for every voltage
previously returned by reg2volt (for the set of possible input values)

Signed-off-by: Luuk Paulussen <luuk.paulussen@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20191205231659.1301-1-luuk.paulussen@alliedtelesis.co.nz
cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Luuk Paulussen 2019-12-06 12:16:59 +13:00 committed by Guenter Roeck
parent e51a7dda29
commit cf3ca18775
1 changed files with 3 additions and 2 deletions
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5
drivers/hwmon/adt7475.c
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@ -294,9 +294,10 @@ static inline u16 volt2reg(int channel, long volt, u8 bypass_attn)
long reg;
if (bypass_attn & (1 << channel))
reg = (volt * 1024) / 2250;
reg = DIV_ROUND_CLOSEST(volt * 1024, 2250);
else
reg = (volt * r[1] * 1024) / ((r[0] + r[1]) * 2250);
reg = DIV_ROUND_CLOSEST(volt * r[1] * 1024,
(r[0] + r[1]) * 2250);
return clamp_val(reg, 0, 1023) & (0xff << 2);
}