[Intel-gfx] drm/i915/slpc: Update freq min/max softlimits

[Chris Wilson]

On Sun, Aug 21, 2016 at 09:39:17PM +0530, Kamble, Sagar A wrote:
> 
> 
> On 8/21/2016 2:09 PM, Chris Wilson wrote:
> >On Sun, Aug 21, 2016 at 11:39:22AM +0530, Kamble, Sagar A wrote:
> >>
> >>On 8/20/2016 1:32 PM, Chris Wilson wrote:
> >>>On Sat, Aug 20, 2016 at 10:39:25AM +0530, Sagar Arun Kamble wrote:
> >>>>+	obj = dev_priv->guc.slpc.vma->obj;
> >>>>+	if (obj) {
> >>>OOPS.
> >>Fixed in next series.
> >>>>+		intel_slpc_query_task_state(dev_priv);
> >>>>+
> >>>>+		page = i915_gem_object_get_page(obj, 0);
> >>>>+		if (page)
> >>>>+			pv = kmap_atomic(page);
> >>>>+	}
> >>>>+
> >>>>+	if (pv) {
> >>>>+		data = *(struct slpc_shared_data *) pv;
> >>>>+		kunmap_atomic(pv);
> >>>Can kmap_atomic return zero?
> >>Fixed in next series.
> >>>>+
> >>>>+		/*
> >>>>+		 * TODO: Define separate variables for slice and unslice
> >>>>+		 *	 frequencies for driver state variable.
> >>>>+		 */
> >>>>+		dev_priv->rps.max_freq_softlimit =
> >>>>+				data.task_state_data.freq_unslice_max;
> >>>>+		dev_priv->rps.min_freq_softlimit =
> >>>>+				data.task_state_data.freq_unslice_min;
> >>>These are user values, you do not get to arbitrarily rewrite them.
> >>>
> >>>You control dev_priv->rps.[min|max]_freq.
> >>With SLPC, GuC firmware SLPC S/W requested frequency be operated in
> >>the softlimits analogous to
> >>Host softlimits. Limits might be different with SLPC and can be
> >>controlled through regular interfaces.
> >>dev_priv->rps.[min|max]_freq are HW Min/Max.
> >Exactly. The soft limits are *only* set by the user. They are not to
> >modified by the driver. (The caveat would be a dynamic update of the hw
> >range, but that too should never be required.)
> >-Chris
> This initialization is similar to following from intel_init_gt_powersave
>         dev_priv->rps.max_freq_softlimit = dev_priv->rps.max_freq;
>         dev_priv->rps.min_freq_softlimit = dev_priv->rps.min_freq;
> I assume min_freq is hw min(RPn). With SLPC, min_freq(RPn) will not
> be requested.
> SLPC operating range today is (>Rpe, Rp0) so I wanted user to know
> the min_softlimit being initialized by SLPC by default.

Hmm, my mistake here was thinking this was more than a one off. Setting
the initial soft (user) range on startup is fine. Continually changing
them after userspace registration is not. (The value the user writes
into the limit is what should be read back - without very good reason,
such as the hard limits changing).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre