[Intel-gfx] [PATCH v2 1/3] drm/i915: Fix up CNL cdclk related limits

[Pandiyan, Dhinakaran]

On Mon, 2017-07-10 at 21:11 +0300, Ville Syrjälä wrote:
> On Mon, Jul 10, 2017 at 05:34:11PM +0000, Pandiyan, Dhinakaran wrote:
> > 
> > 
> > 
> > On Mon, 2017-07-10 at 16:02 +0300, ville.syrjala at linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > 
> > > Follow the GLK path when computing cdclk and related limits. CNL
> > > pipes also produce two pixels per clock, so that's what we should
> > > really use. However for the purposes of pixel rate calculations we
> > > will assume one pixel per clock to keep the voltage higher, at least
> > > until the missing voltage scaling for DDI clocks is implemented.
> > > 
> > 
> > Does the lack of  correct voltage scaling implementation affect only
> > intel_compute_max_dotclk()? i.e., allowing a pixel rate of
> > 2*max_cdclk_freq? Or does it mean cnl_calc_cdclk() cannot take into
> > account pixel_rate <= 2*cdclk_freq for any frequency?
> > 
> > 
> > With this patch, 
> > bdw_adjust_min_pipe_pixel_rate() compares pixel_rate to 2*cdclk
> > cnl_calc_cdclk() compares pixel_rate to 1*cdclk.
> > Isn't that a discrepancy?
> 
> Hmm. Yeah. I suppose I should just squash this with patch 2/3. My
> original intention for this separate patch was to respect the 2x
> limit rather than the 1x limit. But since we couldn't do that I
> suppose the justification for this patch has pretty much gone
> away, and as you point out, it just leads to a mess.
> 
> The combination of patches 1/3+2/3 should still do the right thing
> because we no longer use the pixel rate in the audio workarounds.
> 

I just took a look at 2/3, squashing does solve the problem. I'll review
the combined patch when you send it.

-DK 

> > 
> > 
> > > For the HBR2 vs. audio issue the limit should more correctly be 336
> > > MHz, but the GLK limit of 316.8 MHz works just as well and results
> > > in picking at least 336 MHz. Also toss in some related w/a numbers.
> > 
> > In this case, _adjust_min_pipe_pixel_rate() will return pixel_rate as
> > 633.6 MHz, followed by cnl_calc_cdclk() returning 528 MHz cdclk. But,
> > isn't the correct workaround cdclk 336 MHz?
> > 
> > 
> > > 
> > > v2: Assume 1 pixel per clock for the purposes of max pixel rate
> > >     calculation until DDI clock voltage scaling is handled
> > > 
> > > Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> > > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_cdclk.c | 20 ++++++++++++++------
> > >  1 file changed, 14 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c
> > > index 1241e5891b29..4b8eb6a7d852 100644
> > > --- a/drivers/gpu/drm/i915/intel_cdclk.c
> > > +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> > > @@ -1752,12 +1752,13 @@ static int bdw_adjust_min_pipe_pixel_rate(struct intel_crtc_state *crtc_state,
> > >  	    crtc_state->has_audio &&
> > >  	    crtc_state->port_clock >= 540000 &&
> > >  	    crtc_state->lane_count == 4) {
> > > -		if (IS_CANNONLAKE(dev_priv))
> > > -			pixel_rate = max(316800, pixel_rate);
> > > -		else if (IS_GEMINILAKE(dev_priv))
> > > +		if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv)) {
> > > +			/* Display WA #1145: glk,cnl */
> > >  			pixel_rate = max(2 * 316800, pixel_rate);
> > > -		else
> > > +		} else if (IS_GEN9(dev_priv) || IS_BROADWELL(dev_priv)) {
> > > +			/* Display WA #1144: skl,bxt */
> > >  			pixel_rate = max(432000, pixel_rate);
> > > +		}
> > >  	}
> > >  
> > >  	/* According to BSpec, "The CD clock frequency must be at least twice
> > > @@ -1766,7 +1767,7 @@ static int bdw_adjust_min_pipe_pixel_rate(struct intel_crtc_state *crtc_state,
> > >  	 * two pixels per clock.
> > >  	 */
> > >  	if (crtc_state->has_audio && INTEL_GEN(dev_priv) >= 9) {
> > > -		if (IS_GEMINILAKE(dev_priv))
> > > +		if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
> > >  			pixel_rate = max(2 * 2 * 96000, pixel_rate);
> > >  		else
> > >  			pixel_rate = max(2 * 96000, pixel_rate);
> > > @@ -1999,7 +2000,14 @@ static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv)
> > >  {
> > >  	int max_cdclk_freq = dev_priv->max_cdclk_freq;
> > >  
> > > -	if (IS_GEMINILAKE(dev_priv))
> > > +	if (INTEL_GEN(dev_priv) >= 10)
> > > +		/*
> > > +		 * FIXME: Allow '2 * max_cdclk_freq'
> > > +		 * once DDI clock voltage requirements are
> > > +		 * handled correctly.
> > > +		 */
> > > +		return max_cdclk_freq;
> > > +	else if (IS_GEMINILAKE(dev_priv))
> > >  		/*
> > >  		 * FIXME: Limiting to 99% as a temporary workaround. See
> > >  		 * glk_calc_cdclk() for details.
>