Re: [Intel-gfx] [PATCH 4/4] drm/i915/dsi: Ungate clock before enabling the phy

From: "Kulkarni, Vandita" <vandita.kulkarni@intel.com>
To: "Kulkarni, Vandita" <vandita.kulkarni@intel.com>,
	"Nikula, Jani" <jani.nikula@intel.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>
Cc: "Deak, Imre" <imre.deak@intel.com>,
	"Roper, Matthew D" <matthew.d.roper@intel.com>
Subject: Re: [Intel-gfx] [PATCH 4/4] drm/i915/dsi: Ungate clock before enabling the phy
Date: Tue, 19 Oct 2021 11:43:59 +0000	[thread overview]
Message-ID: <e8ac1de6651549b2a62ea25217ac9cd3@intel.com> (raw)
In-Reply-To: <a9ed33b941ed4a2cb8c8375c0ce81281@intel.com>

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of
> Kulkarni, Vandita
> Sent: Tuesday, October 19, 2021 5:03 PM
> To: Nikula, Jani <jani.nikula@intel.com>; intel-gfx@lists.freedesktop.org
> Cc: Deak, Imre <imre.deak@intel.com>; Roper, Matthew D
> <matthew.d.roper@intel.com>
> Subject: Re: [Intel-gfx] [PATCH 4/4] drm/i915/dsi: Ungate clock before
> enabling the phy
> 
> > -----Original Message-----
> > From: Nikula, Jani <jani.nikula@intel.com>
> > Sent: Tuesday, October 19, 2021 3:48 PM
> > To: Kulkarni, Vandita <vandita.kulkarni@intel.com>; intel-
> > gfx@lists.freedesktop.org
> > Cc: Deak, Imre <imre.deak@intel.com>; Roper, Matthew D
> > <matthew.d.roper@intel.com>; Kulkarni, Vandita
> > <vandita.kulkarni@intel.com>
> > Subject: Re: [PATCH 4/4] drm/i915/dsi: Ungate clock before enabling
> > the phy
> >
> > On Mon, 18 Oct 2021, Vandita Kulkarni <vandita.kulkarni@intel.com>
> wrote:
> > > For the PHY enable/disable signalling to propagate between Dispaly
> > > and PHY, DDI clocks need to be running when enabling the PHY.
> > >
> >
> > A bspec reference would be useful:
> >
> > Bspec: NNN

Bspec: 49187

> >
> > > Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/icl_dsi.c | 8 +++-----
> > >  1 file changed, 3 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c
> > b/drivers/gpu/drm/i915/display/icl_dsi.c
> > > index 8c166f92f8bd..77cd01ecfa80 100644
> > > --- a/drivers/gpu/drm/i915/display/icl_dsi.c
> > > +++ b/drivers/gpu/drm/i915/display/icl_dsi.c
> > > @@ -1135,8 +1135,6 @@ static void
> > >  gen11_dsi_enable_port_and_phy(struct intel_encoder *encoder,
> > >  			      const struct intel_crtc_state *crtc_state)  {
> > > -	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > > -
> > >  	/* step 4a: power up all lanes of the DDI used by DSI */
> > >  	gen11_dsi_power_up_lanes(encoder);
> > >
> > > @@ -1146,6 +1144,8 @@ gen11_dsi_enable_port_and_phy(struct
> > intel_encoder *encoder,
> > >  	/* step 4c: configure voltage swing and skew */
> > >  	gen11_dsi_voltage_swing_program_seq(encoder);
> > >
> > > +	gen11_dsi_ungate_clocks(encoder);
> > > +
> > >  	/* enable DDI buffer */
> > >  	gen11_dsi_enable_ddi_buffer(encoder);
> > >
> > > @@ -1161,9 +1161,7 @@ gen11_dsi_enable_port_and_phy(struct
> > intel_encoder *encoder,
> > >  	/* Step (4h, 4i, 4j, 4k): Configure transcoder */
> > >  	gen11_dsi_configure_transcoder(encoder, crtc_state);
> > >
> > > -	/* Step 4l: Gate DDI clocks */
> > > -	if (DISPLAY_VER(dev_priv) == 11)
> > > -		gen11_dsi_gate_clocks(encoder);
> > > +	gen11_dsi_gate_clocks(encoder);
> >
> > So how does this relate to
> > 991d9557b0c4 ("drm/i915/tgl/dsi: Gate the ddi clocks after pll
> > mapping")
> 
> As per the latest bspec, this change doesn't seem to be valid anymore.
> It is marked with removed tag.
> When TGL got added this change came in.
> 
> But now with ADL the whole thing is marked as removed.

And the gating is now added after enabling DDI Buffer 

> So, Do you suggest that I submit a revert for this change ?
> 
> Thanks,
> Vandita
> >
> > >  }
> > >
> > >  static void gen11_dsi_powerup_panel(struct intel_encoder *encoder)
> >
> > --
> > Jani Nikula, Intel Open Source Graphics Center