On 10/13/2021 7:28 PM, Alex Deucher wrote:
On Wed, Oct 13, 2021 at 12:14 AM Lazar, Lijo <lijo.lazar@xxxxxxx> wrote:
On 10/13/2021 8:40 AM, Luben Tuikov wrote:
Some ASIC support low-power functionality for the whole ASIC or just
an IP block. When in such low-power mode, some sysfs interfaces would
report a frequency of 0, e.g.,
$cat /sys/class/drm/card0/device/pp_dpm_sclk
0: 500Mhz
1: 0Mhz *
2: 2200Mhz
$_
An operating frequency of 0 MHz doesn't make sense, and this interface
is designed to report only operating clock frequencies, i.e. non-zero,
and possibly the current one.
When in this low-power state, round to the smallest
operating frequency, for this interface, as follows,
Would rather avoid this -
1) It is manipulating FW reported value. If at all there is an uncaught
issue in FW reporting of frequency values, that is masked here.
2) Otherwise, if 0MHz is described as GFX power gated case, this
provides a convenient interface to check if GFX is power gated.
If seeing a '0' is not pleasing, consider changing to something like
"NA" - not available (frequency cannot be fetched at the moment).
I don't think this interface is really supposed to be the way to get
the current clock, although some use it that way. It's supposed to
show the DPM states and which are active. conflating the interface
with other information confuses things in my opinion. Why is the
current clock less than the minimum clock? Whether or not an IP is
turned off or in deep sleep or not is independent of DPM states. When
the IP is active, it will never go below the minimum DPM level. If we
want to query deep sleep or gfxoff we can use the amdgpu_pm_info
debugfs interface or add some other new interface.
The idea of DPM level is deprecated with fine grained clock which
provides only min and max. For fine grained clock, we fetch the current
clock frequency and show it as an artificial DPM level between min/max.
That itself should have confused users but it is not which means the
users use the * to fetch the current frequency and not really bothered
about the DPM level per se.
Also, some ASICs define 'min' as as the least possible freq (that
happens during a throttle) and not the DPM level 0 min in the
traditional sense (that is defined as idle frequency which doesn't come
into min/max levels). It's usually from the idle frequency that GFX gets
power gated. Showing a * against min in such cases would be confusing
because that could be misinterpreted as a throttle scenario.
Thanks,
Lijo
Alex
Thanks,
Lijo
$cat /sys/class/drm/card0/device/pp_dpm_sclk
0: 500Mhz *
1: 2200Mhz
$_
Luben Tuikov (5):
drm/amd/pm: Slight function rename
drm/amd/pm: Rename cur_value to curr_value
drm/amd/pm: Rename freq_values --> freq_value
dpm/amd/pm: Sienna: 0 MHz is not a current clock frequency
dpm/amd/pm: Navi10: 0 MHz is not a current clock frequency
.../gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c | 60 +++++++++------
.../amd/pm/swsmu/smu11/sienna_cichlid_ppt.c | 73 ++++++++++++-------
2 files changed, 86 insertions(+), 47 deletions(-)
