RE: [PATCH] drm/amdgpu: Add sysfs file for VBIOS

["Deucher, Alexander" <Alexander.Deucher-5C7GfCeVMHo@public.gmane.org>]

> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces@lists.freedesktop.org] On Behalf
> Of Felix Kuehling
> Sent: Friday, August 25, 2017 3:34 PM
> To: amd-gfx@lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: Add sysfs file for VBIOS
> 
> I think the power measurement is a bit of a hack right now. It requires
> pinging the SMU twice to start and stop the measurement, and waiting for
> some time (but not too long) in between. I think if we want to expose
> this via hwmon, we'll need to have some kind of timer that polls it in
> regular intervals in the background and updates a value that can be
> queried through HWMon without delay.

I don't know that hwmon has any requirements with respect to delay.  I think a slight delay in reading it back through hwmon is preferable to a background thread polling it. Regular polling may also have negative impacts on performance or stability, depending on how it was validated.

Alex

> 
> Regards,
>   Felix
> 
> 
> On 2017-08-25 11:56 AM, Deucher, Alexander wrote:
> >> -----Original Message-----
> >> From: amd-gfx [mailto:amd-gfx-bounces@lists.freedesktop.org] On
> Behalf
> >> Of Russell, Kent
> >> Sent: Friday, August 25, 2017 9:00 AM
> >> To: StDenis, Tom; Christian König; amd-gfx@lists.freedesktop.org
> >> Subject: RE: [PATCH] drm/amdgpu: Add sysfs file for VBIOS
> >>
> >> There is GPU Power usage reported through amdgpu_pm_info, which
> also
> >> has some other information as well. I'd like that in sysfs, but I am unsure if
> >> we are  allowed to due to the other information reported there.
> > For power and voltage, I believe there are standard hwmon interfaces.  It
> would probably be best to expose it via those.  For clocks/pcie, I think you
> can already determine them via the existing pp sysfs interfaces.
> >
> > Alex
> >
> >>  Kent
> >>
> >> -----Original Message-----
> >> From: StDenis, Tom
> >> Sent: Friday, August 25, 2017 8:58 AM
> >> To: Christian König; Russell, Kent; amd-gfx@lists.freedesktop.org
> >> Subject: Re: [PATCH] drm/amdgpu: Add sysfs file for VBIOS
> >>
> >> On 25/08/17 08:56 AM, Christian König wrote:
> >>> Hi Kent,
> >>>
> >>> agree on the VBIOS dump file, that clearly belongs to debugsf.
> >>>
> >>> The power usage stuff I can't say much about cause I'm not deeply into
> >>> this, but keep in mind the restriction for sysfs:
> >>> 1. It's a stable interface. So it must be very well designed.
> >>> 2. Only one value per file. I think the power stuff doesn't fulfill
> >>> that requirement at the moment.
> >> What "power" stuff are we talking about?  The sensors interface or the
> >> pm_info or something else?
> >>
> >> Keep in mind umr uses the sensors debugfs file in --top mode.
> >>
> >> Tom
> >> _______________________________________________
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