Re: [PATCH 3/3] drm/i915: Share cdclk code for BDW and BXT

Ville Syrjälä
2015-10-27T14:31:59Z

On Tue, Oct 27, 2015 at 03:43:03PM +0200, Jani Nikula wrote:
> On Tue, 27 Oct 2015, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > The difference betwen the BXT and BDW cdclk code boils down to two
> > things: claming the cdclk to the maximum supported, and panel fitter
> > downscaling ratio
> >
> > Unifying the the max cdclk clamping is easy, just do it.
> >
> > And as far as the panel fitter is concerned, SKL+ already (ab)use the
> > pch pfit state for its pipe scaler information, so it will compute the
> > adjusted pixel rate correctly.
> >
> > So we can just use the BDW code for BXT, as long as we lift the BXT
> > pixel rate -> cdclk selection into the correct place.
>
> I don't like the direction taken by this patch.
>
> We have the platform specific functions to keep stuff platform
> specific. Now you claim bdw and bxt are almost the same, yet the
> functions are filled with conditionals on the platform. I value having
> straightforward and readable platform specific hooks much higher than
> the slight reduction in line count.

I agree that it's not all that nice. The real problem is that the current
cdclk function pointers are just too high level. They really should
be at the calc_cdclk and set_cdclk level. But fixing that would require
actually dealing with the gmch pfit, and stuffing the power domain
hack (assuming we still need it) and the pfi programming for vlv/chv
into the lower level functions. And looks like no one has bothered to do
any of that.

>
> BR,
> Jani.
>
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_display.c | 87 +++++++++++++-----------------------
> > 1 file changed, 30 insertions(+), 57 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 978f543..0c782c7 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -5932,25 +5932,6 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
> > return 200000;
> > }
> >
> > -static int broxton_calc_cdclk(struct drm_i915_private *dev_priv,
> > - int max_pixclk)
> > -{
> > - /*
> > - * FIXME:
> > - * - set 19.2MHz bypass frequency if there are no active pipes
> > - */
> > - if (max_pixclk > 576000)
> > - return 624000;
> > - else if (max_pixclk > 384000)
> > - return 576000;
> > - else if (max_pixclk > 288000)
> > - return 384000;
> > - else if (max_pixclk > 144000)
> > - return 288000;
> > - else
> > - return 144000;
> > -}
> > -
> > /* Compute the max pixel clock for new configuration. Uses atomic state if
> > * that's non-NULL, look at current state otherwise. */
> > static int intel_mode_max_pixclk(struct drm_device *dev,
> > @@ -5990,21 +5971,6 @@ static int valleyview_modeset_calc_cdclk(struct drm_atomic_state *state)
> > return 0;
> > }
> >
> > -static int broxton_modeset_calc_cdclk(struct drm_atomic_state *state)
> > -{
> > - struct drm_device *dev = state->dev;
> > - struct drm_i915_private *dev_priv = dev->dev_private;
> > - int max_pixclk = intel_mode_max_pixclk(dev, state);
> > -
> > - if (max_pixclk < 0)
> > - return max_pixclk;
> > -
> > - to_intel_atomic_state(state)->cdclk =
> > - broxton_calc_cdclk(dev_priv, max_pixclk);
> > -
> > - return 0;
> > -}
> > -
> > static void vlv_program_pfi_credits(struct drm_i915_private *dev_priv)
> > {
> > unsigned int credits, default_credits;
> > @@ -9497,14 +9463,6 @@ void hsw_disable_pc8(struct drm_i915_private *dev_priv)
> > intel_prepare_ddi(dev);
> > }
> >
> > -static void broxton_modeset_commit_cdclk(struct drm_atomic_state *old_state)
> > -{
> > - struct drm_device *dev = old_state->dev;
> > - unsigned int req_cdclk = to_intel_atomic_state(old_state)->cdclk;
> > -
> > - broxton_set_cdclk(dev, req_cdclk);
> > -}
> > -
> > /* compute the max rate for new configuration */
> > static int ilk_max_pixel_rate(struct drm_atomic_state *state)
> > {
> > @@ -9621,14 +9579,31 @@ static int broadwell_modeset_calc_cdclk(struct drm_atomic_state *state)
> > * FIXME should also account for plane ratio
> > * once 64bpp pixel formats are supported.
> > */
> > - if (max_pixclk > 540000)
> > - cdclk = 675000;
> > - else if (max_pixclk > 450000)
> > - cdclk = 540000;
> > - else if (max_pixclk > 337500)
> > - cdclk = 450000;
> > - else
> > - cdclk = 337500;
> > + if (IS_BROXTON(dev_priv)) {
> > + /*
> > + * FIXME:
> > + * - set 19.2MHz bypass frequency if there are no active pipes
> > + */
> > + if (max_pixclk > 576000)
> > + cdclk = 624000;
> > + else if (max_pixclk > 384000)
> > + cdclk = 576000;
> > + else if (max_pixclk > 288000)
> > + cdclk = 384000;
> > + else if (max_pixclk > 144000)
> > + cdclk = 288000;
> > + else
> > + cdclk = 144000;
> > + } else {
> > + if (max_pixclk > 540000)
> > + cdclk = 675000;
> > + else if (max_pixclk > 450000)
> > + cdclk = 540000;
> > + else if (max_pixclk > 337500)
> > + cdclk = 450000;
> > + else
> > + cdclk = 337500;
> > + }
> >
> > /*
> > * FIXME move the cdclk caclulation to
> > @@ -9650,7 +9625,10 @@ static void broadwell_modeset_commit_cdclk(struct drm_atomic_state *old_state)
> > struct drm_device *dev = old_state->dev;
> > unsigned int req_cdclk = to_intel_atomic_state(old_state)->cdclk;
> >
> > - broadwell_set_cdclk(dev, req_cdclk);
> > + if (IS_BROXTON(dev))
> > + broxton_set_cdclk(dev, req_cdclk);
> > + else
> > + broadwell_set_cdclk(dev, req_cdclk);
> > }
> >
> > static int haswell_crtc_compute_clock(struct intel_crtc *crtc,
> > @@ -14619,7 +14597,7 @@ static void intel_init_display(struct drm_device *dev)
> > dev_priv->display.fdi_link_train = hsw_fdi_link_train;
> > }
> >
> > - if (IS_BROADWELL(dev)) {
> > + if (IS_BROADWELL(dev) || IS_BROXTON(dev)) {
> > dev_priv->display.modeset_commit_cdclk =
> > broadwell_modeset_commit_cdclk;
> > dev_priv->display.modeset_calc_cdclk =
> > @@ -14629,11 +14607,6 @@ static void intel_init_display(struct drm_device *dev)
> > valleyview_modeset_commit_cdclk;
> > dev_priv->display.modeset_calc_cdclk =
> > valleyview_modeset_calc_cdclk;
> > - } else if (IS_BROXTON(dev)) {
> > - dev_priv->display.modeset_commit_cdclk =
> > - broxton_modeset_commit_cdclk;
> > - dev_priv->display.modeset_calc_cdclk =
> > - broxton_modeset_calc_cdclk;
> > }
> >
> > switch (INTEL_INFO(dev)->gen) {
>
> --
> Jani Nikula, Intel Open Source Technology Center

--
Ville Syrjälä
Intel OTC