4ed22f1e52
On ATSM the PL1 limit is disabled at power up. The previous uapi assumed
that the PL1 limit is always enabled and therefore did not have a notion of
a disabled PL1 limit. This results in erroneous PL1 limit values when the
PL1 limit is disabled. For example at power up, the disabled ATSM PL1 limit
was previously shown as 0 which means a low PL1 limit whereas the limit
being disabled actually implies a high effective PL1 limit value.
To get round this problem, the PL1 limit uapi is expanded to include a
special value 0 to designate a disabled PL1 limit. A read value of 0 means
that the PL1 power limit is disabled, writing 0 disables the limit.
The link between this patch and the bugs mentioned below is as follows:
* Because on ATSM the PL1 power limit is disabled on power up and there
were no means to enable it, we previously implemented the means to
enable the limit when the PL1 hwmon entry (power1_max) was written to.
* Now there is a IGT igt@i915_hwmon@hwmon_write which (a) reads orig value
from all hwmon sysfs (b) does a bunch of random writes and finally (c)
restores the orig value read. On ATSM since the orig value is 0, when
the IGT restores the 0 value, the PL1 limit is now enabled with a value
of 0.
* PL1 limit of 0 implies a low PL1 limit which causes GPU freq to fall to
100 MHz. This causes GuC FW load and several IGT's to start timing out
and gives rise to these Intel CI bugs. After this patch, writing 0 would
disable the PL1 limit instead of enabling it, avoiding the freq drop
issue.
v2: Add explanation for bugs mentioned below (Rodrigo)
v3: Eliminate race during PL1 disable and verify (Tvrtko)
Change return to -ENODEV if verify fails (Tvrtko)
Link: https://gitlab.freedesktop.org/drm/intel/-/issues/8062
Link: https://gitlab.freedesktop.org/drm/intel/-/issues/8060
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230401024146.1826092-1-ashutosh.dixit@intel.com
2.7 KiB
What: /sys/devices/.../hwmon/hwmon/in0_input Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RO. Current Voltage in millivolt.
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/power1_max Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RW. Card reactive sustained (PL1/Tau) power limit in microwatts.
The power controller will throttle the operating frequency
if the power averaged over a window (typically seconds)
exceeds this limit. A read value of 0 means that the PL1
power limit is disabled, writing 0 disables the
limit. Writing values > 0 will enable the power limit.
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/power1_rated_max Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RO. Card default power limit (default TDP setting).
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/power1_max_interval Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RW. Sustained power limit interval (Tau in PL1/Tau) in milliseconds over which sustained power is averaged.
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/power1_crit Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RW. Card reactive critical (I1) power limit in microwatts.
Card reactive critical (I1) power limit in microwatts is exposed
for client products. The power controller will throttle the
operating frequency if the power averaged over a window exceeds
this limit.
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/curr1_crit Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RW. Card reactive critical (I1) power limit in milliamperes.
Card reactive critical (I1) power limit in milliamperes is
exposed for server products. The power controller will throttle
the operating frequency if the power averaged over a window
exceeds this limit.
Only supported for particular Intel i915 graphics platforms.
What: /sys/devices/.../hwmon/hwmon/energy1_input Date: February 2023 KernelVersion: 6.2 Contact: intel-gfx@lists.freedesktop.org Description: RO. Energy input of device or gt in microjoules.
For i915 device level hwmon devices (name "i915") this
reflects energy input for the entire device. For gt level
hwmon devices (name "i915_gtN") this reflects energy input
for the gt.
Only supported for particular Intel i915 graphics platforms.