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

["Kulkarni, Vandita" <vandita.kulkarni@intel.com>]

> -----Original Message-----
> From: Nikula, Jani <jani.nikula@intel.com>
> Sent: Tuesday, October 19, 2021 5:16 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>
> Subject: RE: [PATCH 4/4] drm/i915/dsi: Ungate clock before enabling the phy
> 
> On Tue, 19 Oct 2021, "Kulkarni, Vandita" <vandita.kulkarni@intel.com>
> wrote:
> >> -----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
> >>
> >> > 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.
> > So, Do you suggest that I submit a revert for this change ?
> 
> No, just an explanation and maybe that commit reference in the commit
> message.

Okay, will do that.

Thanks,
Vandita 
> 
> BR,
> Jani.
> 
> >
> > Thanks,
> > Vandita
> >>
> >> >  }
> >> >
> >> >  static void gen11_dsi_powerup_panel(struct intel_encoder *encoder)
> >>
> >> --
> >> Jani Nikula, Intel Open Source Graphics Center
> 
> --
> Jani Nikula, Intel Open Source Graphics Center