RE: [PATCH 1/3] drm/i915/ddi: add helper to compute DDI clock frequency

> Subject: Re: [PATCH 1/3] drm/i915/ddi: add helper to compute DDI clock
> frequency
> 
> On Tue, 11 Aug 2026, Suraj Kandpal <[email protected]> wrote:
> > Add intel_ddi_link_symbol_clock() to return the DDI clock frequency
> > for a given port clock:
> >   DP 8b/10b : rate / 10
> 
> rate
> 
> >   DP 128b/132b (UHBR) : rate / 32
> 
> (10/32) * rate
> 
> >   HDMI FRL  : rate / 18
> 
> (10/18) * rate
> 
> >   HDMI TMDS : rate
> 

Sure will update these

Regards,
Suraj Kandpal

> >
> > The DP case reuses intel_dp_link_symbol_clock().
> > This will help in upcoming commits to decide value to be written in
> > DDI_CLK_VALFREQ.
> >
> > Signed-off-by: Suraj Kandpal <[email protected]>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c | 11 +++++++++++
> > drivers/gpu/drm/i915/display/intel_ddi.h |  1 +
> >  2 files changed, 12 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c
> > b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index bf5788c5bbd3..dd9064592ec9 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -1529,6 +1529,17 @@ int intel_ddi_level(struct intel_encoder *encoder,
> >  	return level;
> >  }
> >
> > +int intel_ddi_link_symbol_clock(struct intel_encoder *encoder, int
> > +clock) {
> > +	if (intel_encoder_is_dp(encoder))
> > +		return intel_dp_link_symbol_clock(clock);
> > +
> > +	if (intel_hdmi_is_frl(clock))
> > +		return DIV_ROUND_CLOSEST(clock * 10, 18);
> > +
> > +	return clock;
> > +}
> > +
> >  static void
> >  hsw_set_signal_levels(struct intel_encoder *encoder,
> >  		      const struct intel_crtc_state *crtc_state) diff --git
> > a/drivers/gpu/drm/i915/display/intel_ddi.h
> > b/drivers/gpu/drm/i915/display/intel_ddi.h
> > index 580ecb09b8b6..239d5a403f91 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.h
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.h
> > @@ -81,6 +81,7 @@ void intel_ddi_sanitize_encoder_pll_mapping(struct
> > intel_encoder *encoder);  int intel_ddi_level(struct intel_encoder *encoder,
> >  		    const struct intel_crtc_state *crtc_state,
> >  		    int lane);
> > +int intel_ddi_link_symbol_clock(struct intel_encoder *encoder, int
> > +clock);
> >  void intel_ddi_update_active_dpll(struct intel_atomic_state *state,
> >  				  struct intel_encoder *encoder,
> >  				  struct intel_crtc *crtc);
> 
> --
> Jani Nikula, Intel