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Subject[PATCH] hwmon: corsair-psu: update calculation of LINEAR11 values
Changes the way how LINEAR11 values are calculated. The new method
increases the precision of 2-3 digits.

old method:
corsairpsu-hid-3-1
Adapter: HID adapter
v_in: 230.00 V
v_out +12v: 12.00 V
v_out +5v: 5.00 V
v_out +3.3v: 3.00 V
psu fan: 0 RPM
vrm temp: +44.0°C
case temp: +37.0°C
power total: 152.00 W
power +12v: 112.00 W
power +5v: 38.00 W
power +3.3v: 5.00 W
curr in: N/A
curr +12v: 9.00 A
curr +5v: 7.00 A
curr +3.3v: 1000.00 mA

new method:
corsairpsu-hid-3-1
Adapter: HID adapter
v_in: 230.00 V
v_out +12v: 12.16 V
v_out +5v: 5.01 V
v_out +3.3v: 3.30 V
psu fan: 0 RPM
vrm temp: +44.5°C
case temp: +37.8°C
power total: 148.00 W
power +12v: 108.00 W
power +5v: 37.00 W
power +3.3v: 4.50 W
curr in: N/A
curr +12v: 9.25 A
curr +5v: 7.50 A
curr +3.3v: 1.50 A

Co-developed-by: Jack Doan <me@jackdoan.com>
Signed-off-by: Jack Doan <me@jackdoan.com>
Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
---
drivers/hwmon/corsair-psu.c | 30 ++++++++----------------------
1 file changed, 8 insertions(+), 22 deletions(-)

diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
index 99494056f4bd..b0953eeeb2d3 100644
--- a/drivers/hwmon/corsair-psu.c
+++ b/drivers/hwmon/corsair-psu.c
@@ -119,27 +119,13 @@ struct corsairpsu_data {
};

/* some values are SMBus LINEAR11 data which need a conversion */
-static int corsairpsu_linear11_to_int(const int val)
+static int corsairpsu_linear11_to_int(const u16 val, const int scale)
{
- int exp = (val & 0xFFFF) >> 0x0B;
- int mant = val & 0x7FF;
- int i;
-
- if (exp > 0x0F)
- exp -= 0x20;
- if (mant > 0x3FF)
- mant -= 0x800;
- if ((mant & 0x01) == 1)
- ++mant;
- if (exp < 0) {
- for (i = 0; i < -exp; ++i)
- mant /= 2;
- } else {
- for (i = 0; i < exp; ++i)
- mant *= 2;
- }
+ const int exp = ((s16)val) >> 11;
+ const int mant = (((s16)(val & 0x7ff)) << 5) >> 5;
+ const int result = mant * scale;

- return mant;
+ return (exp >= 0) ? (result << exp) : (result >> -exp);
}

static int corsairpsu_usb_cmd(struct corsairpsu_data *priv, u8 p0, u8 p1, u8 p2, void *data)
@@ -249,14 +235,14 @@ static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, l
case PSU_CMD_RAIL_AMPS:
case PSU_CMD_TEMP0:
case PSU_CMD_TEMP1:
- *val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000;
+ *val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1000);
break;
case PSU_CMD_FAN:
- *val = corsairpsu_linear11_to_int(tmp & 0xFFFF);
+ *val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1);
break;
case PSU_CMD_RAIL_WATTS:
case PSU_CMD_TOTAL_WATTS:
- *val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000000;
+ *val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1000000);
break;
case PSU_CMD_TOTAL_UPTIME:
case PSU_CMD_UPTIME:
--
2.30.1
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