Re: [Intel-gfx] [PATCH v2 05/20] drm/i915: Make skl_compute_dbuf_slices() behave consistently for all platforms

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Mon, Mar 02, 2020 at 04:50:37PM +0200, Ville Syrjälä wrote:
> On Tue, Feb 25, 2020 at 05:30:57PM +0000, Lisovskiy, Stanislav wrote:
> > On Tue, 2020-02-25 at 19:11 +0200, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > Currently skl_compute_dbuf_slices() returns 0 for any inactive pipe
> > > on
> > > icl+, but returns BIT(S1) on pre-icl for any pipe (whether it's
> > > active or
> > > not). Let's make the behaviour consistent and always return 0 for any
> > > inactive pipe.
> > > 
> > > Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_pm.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > > b/drivers/gpu/drm/i915/intel_pm.c
> > > index a2e78969c0df..640f4c4fd508 100644
> > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > @@ -4408,7 +4408,7 @@ static u8 skl_compute_dbuf_slices(const struct
> > > intel_crtc_state *crtc_state,
> > >  	 * For anything else just return one slice yet.
> > >  	 * Should be extended for other platforms.
> > >  	 */
> > > -	return BIT(DBUF_S1);
> > > +	return active_pipes & BIT(pipe) ? BIT(DBUF_S1) : 0;
> > 
> > I think the initial idea was this won't be even called if there 
> > are no active pipes at all - skl_ddb_get_pipe_allocation_limits would
> > bail out immediately. If there were some active pipes - then we will
> > have to use slice S1 anyway - because there were simply no other slices
> > available. If some pipes were inactive - they are currently skipped by
> > !crtc_state->hw.active check - so I would just keep it simple and don't
> > call this function for non-active pipes at all.
> 
> That's just going to make the caller more messy by forcing it to
> check for active_pipes 0 vs. not. Ie. we'd be splitting the
> responsibility of computing the dbuf slices for this pipe between
> skl_compute_dbuf_slices() and its caller. Not a good idea IMO.

Let's ramp it up. As I understood from your comments we still need dbuf_state.
I would anyway add another table for handling this in some unified manner at least,
however don't want to spend another couple of month discussing that :)

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>


> 
> -- 
> Ville Syrjälä
> Intel
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