[Bug 110213] Used pwm value is lesser than the requested value

[Bug 110213] Used pwm value is lesser than the requested value

[bugzilla-daemon]

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https://bugs.freedesktop.org/show_bug.cgi?id=110213

            Bug ID: 110213
           Summary: Used pwm value is lesser than the requested value
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/AMDgpu
          Assignee: dri-devel@lists.freedesktop.org
          Reporter: jpalaciosdev@gmail.com

Created attachment 143743
  --> https://bugs.freedesktop.org/attachment.cgi?id=143743&action=edit
dmesg

On manual fan control through pwm interface, the used value on pwm1 is lesser
that the requested value (except for maximum).
For example:
echo 1 > /sys/class/drm/card0/device/hwmon/hwmon1/pwm1_enable

echo 10 > /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
cat /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
5

echo 100 > /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
cat /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
96

echo 254 > /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
cat /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
249

The maximum value works as expected:
echo 255 > /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
cat /sys/class/drm/card0/device/hwmon/hwmon1/pwm1
255

Other info:
Hardware: MSI RX480 Gaming (Polaris)
Kernel: linux 5.0.2

Please, let me know if more info is needed.
Thanks.

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[Bug 110213] Used pwm value is lesser than the requested value

[bugzilla-daemon]

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https://bugs.freedesktop.org/show_bug.cgi?id=110213

Alex Deucher <alexdeucher@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |NOTABUG

--- Comment #1 from Alex Deucher <alexdeucher@gmail.com> ---
The hwmon API specifies the range as 0-255, but the hw actually has a different
range.  The conversion between ranges for read and writes accounts for the
difference.  See smu7_fan_ctrl_get_fan_speed_percent() and
smu7_fan_ctrl_set_fan_speed_percent() smu7_thermal.c and
amdgpu_hwmon_get_pwm1() and amdgpu_hwmon_set_pwm1() amdgpu_pm.c.

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