[Intel-gfx] [RFC 3/3] drm/i915/icl: Calculate DPLL params for DSI

[Ville Syrjälä]

On Thu, Sep 20, 2018 at 08:49:52AM +0000, Kulkarni, Vandita wrote:
> 
> 
> > -----Original Message-----
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Sent: Friday, September 14, 2018 9:39 PM
> > To: Kulkarni, Vandita <vandita.kulkarni at intel.com>
> > Cc: intel-gfx at lists.freedesktop.org; Nikula, Jani <jani.nikula at intel.com>;
> > Zanoni, Paulo R <paulo.r.zanoni at intel.com>
> > Subject: Re: [Intel-gfx] [RFC 3/3] drm/i915/icl: Calculate DPLL params for DSI
> > 
> > On Fri, Sep 14, 2018 at 12:24:14PM +0530, Vandita Kulkarni wrote:
> > > From: Madhav Chauhan <madhav.chauhan at intel.com>
> > >
> > > This patch calculate various DPLL dividers and parameters for DSI
> > > encoder and adjust AFE clock for DSI. For DSI, 8x clock is AFE clock.
> > >
> > > v2: Extend haswell_crtc_compute_clock() for Gen11 DSI
> > > v3: Rebase
> > >
> > > Signed-off-by: Madhav Chauhan <madhav.chauhan at intel.com>
> > > Signed-off-by: Vandita Kulkarni <vandita.kulkarni at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c  | 4 +++-
> > > drivers/gpu/drm/i915/intel_dpll_mgr.c | 7 ++++++-
> > >  2 files changed, 9 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > > b/drivers/gpu/drm/i915/intel_display.c
> > > index 6928dcc..1a44c5e 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -9238,10 +9238,12 @@ void hsw_disable_pc8(struct drm_i915_private
> > > *dev_priv)  static int haswell_crtc_compute_clock(struct intel_crtc *crtc,
> > >  				      struct intel_crtc_state *crtc_state)  {
> > > +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> > >  	struct intel_atomic_state *state =
> > >  		to_intel_atomic_state(crtc_state->base.state);
> > >
> > > -	if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DSI)) {
> > > +	if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DSI) ||
> > > +				 IS_ICELAKE(dev_priv)) {
> > >  		struct intel_encoder *encoder =
> > >  			intel_get_crtc_new_encoder(state, crtc_state);
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > index 36ed155..5175e44 100644
> > > --- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > +++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > @@ -22,6 +22,7 @@
> > >   */
> > >
> > >  #include "intel_drv.h"
> > > +#include "intel_dsi.h"
> > >
> > >  /**
> > >   * DOC: Display PLLs
> > > @@ -2532,7 +2533,11 @@ static bool icl_calc_dpll_state(struct
> > intel_crtc_state *crtc_state,
> > >  		ret = icl_calc_tbt_pll(dev_priv, clock, &pll_params);
> > >  	else if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI))
> > >  		ret = cnl_ddi_calculate_wrpll(clock, dev_priv, &pll_params);
> > > -	else
> > > +	else if (encoder->type == INTEL_OUTPUT_DSI) {
> > > +		struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
> > > +		ret = cnl_ddi_calculate_wrpll(intel_dsi->bitrate_khz/5,
> > 
> > Missing port_clock=whatever in compute config?
> As per the spec I see that for mipi dsi on icl,
> 8x clock = AFE clock.
> And 8x clock is calculated and stored already as pixel_clk * bpp / lane_count
> Hence we are using already calculate 8x clock variable here and divide by/5 because later in the function it
> gets multiplied by 5 for afe clock.
> 
> port_clock is assigned to pixel clock as I see. 

port_clock can basically be anything you want. It's really up to the
encoder to define it. For DP it's the freq (1.62ghz, 2.7ghz, etc.), for
HDMI it's the TMDS character rate, for SDVO it's the multiplied pixel
clock, etc.

I suppose that means that currently port_clock is the output from the
dpll in pretty much all cases. Sticking to that same rule will make DSI
look less special and thus easier to understand for everyone.

> Please let me know if we have to use math around the port clock and pass that value, than passing 8x clock.
> 
> Thanks,
> Vandita
> > 
> > > +					      dev_priv, &pll_params);
> > > +	} else
> > >  		ret = icl_calc_dp_combo_pll(dev_priv, clock, &pll_params);
> > >
> > >  	if (!ret)
> > > --
> > > 1.9.1
> > >
> > > _______________________________________________
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> > > Intel-gfx at lists.freedesktop.org
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> > 
> > --
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel