Re: [Intel-gfx] [PATCH] drm/i915: Disable DC5 before going to DC9

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Apr 20, 2022 at 10:21:19PM +0300, Imre Deak wrote:
> On Wed, Apr 20, 2022 at 03:09:21PM -0400, Rodrigo Vivi wrote:
> > According to BSPec:
> > 	Sequence to Allow DC9:
> > 		1. Follow Sequence to Disallow DC5.
> > 
> > which is:
> > 	Sequence to Disallow DC5 and DC6
> > 		Set DC_STATE_EN Dynamic DC State Enable = "Disable".
> > 
> > I understand that we haven't had any issue so far. But since
> > DC9 is a software thing, it is better to disable DC5 before
> > to avoid any conflict. And respect the spec to avoid potential
> > future issues.
> > 
> > Cc: Imre Deak <imre.deak@intel.com>
> > Cc: Anshuman Gupta <anshuman.gupta@intel.com>
> > Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display_power.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
> > index 6a5695008f7c..b3cf5182044f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_power.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display_power.c
> > @@ -883,6 +883,9 @@ static void bxt_enable_dc9(struct drm_i915_private *dev_priv)
> >  {
> >  	assert_can_enable_dc9(dev_priv);
> >  
> > +	/* Disable DC5 before enabling DC9 */
> > +	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
> 
> For DC9 DMC should be disabled already, along with DC states and other
> dependencies like power well 1, etc. That happens in
> bxt/icl_display_core_uninit().

but that wasn't on the suspend_late path... but Anusha is right and
probably the check in the assert is already enough for now... if we
notice that assert is coming we do something else...

I was willing to avoid indirection and the risk of changing something
and this dc5 disable getting forgotten, but with the assert we are
probably good...

let's just ignore this patch...

> 
> > +
> >  	drm_dbg_kms(&dev_priv->drm, "Enabling DC9\n");
> >  	/*
> >  	 * Power sequencer reset is not needed on
> > -- 
> > 2.34.1
> >