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

commit cf3ca18775 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Luuk Paulussen 2019-12-06 12:16:59 +13:00 committed by Greg Kroah-Hartman
parent 2d00fec60c
commit 0387ee1b95
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);
}