Re: [PATCH 2/3] drm/i915: fix CFB size calculation

Zanoni, Paulo R
2015-10-01T17:48:28Z

Em Qui, 2015-10-01 às 15:23 +0300, Ville Syrjälä escreveu:
> On Thu, Oct 01, 2015 at 03:14:13PM +0300, Ville Syrjälä wrote:
> > On Wed, Sep 30, 2015 at 05:05:44PM -0300, Paulo Zanoni wrote:
> > > We were considering the whole framebuffer height, but the spec
> > > says we
> > > should only consider the active display height size. There were
> > > still
> > > some unclear questions based on the spec, but the hardware guys
> > > clarified them for us. According to them:
> > >
> > > - CFB size = CFB stride * Number of lines FBC writes to CFB
> > > - CFB stride = plane stride / compression limit
> > > - Number of lines FBC writes to CFB = MIN(plane source height,
> > > maximum
> > > number of lines FBC writes to CFB)
> > > - Plane source height =
> > > - pipe source height (PIPE_SRCSZ register) (before SKL)
> > > - plane size register height (PLANE_SIZE register) (SKL+)
> > > - Maximum number of lines FBC writes to CFB =
> > > - plane source height (before HSW)
> > > - 2048 (HSW+)
> > >
> > > For the plane source height, I could just have made our code do
> > > I915_READ() in order to be more future proof, but since it's not
> > > cool
> > > to do register reads I decided to just recalculate the values we
> > > use
> > > when we actually write to those registers.
> > >
> > > With this patch, depending on your machine configuration, a lot
> > > of the
> > > kms_frontbuffer_tracking subtests that used to result in a SKIP
> > > due to
> > > not enough stolen memory still start resulting in a PASS.
> > >
> > > v2: Use the clipped src size instead of pipe_src_h (Ville).
> > > v3: Use the appropriate information provided by the hardware
> > > guys.
> > >
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > > ---
> > > drivers/gpu/drm/i915/intel_fbc.c | 58
> > > +++++++++++++++++++++++++++++++++++++---
> > > 1 file changed, 54 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_fbc.c
> > > b/drivers/gpu/drm/i915/intel_fbc.c
> > > index 1b2ebb2..d53f73f 100644
> > > --- a/drivers/gpu/drm/i915/intel_fbc.c
> > > +++ b/drivers/gpu/drm/i915/intel_fbc.c
> > > @@ -698,9 +698,60 @@ void intel_fbc_cleanup_cfb(struct
> > > drm_i915_private *dev_priv)
> > > mutex_unlock(&dev_priv->fbc.lock);
> > > }
> > >
> > > -static int intel_fbc_setup_cfb(struct drm_i915_private
> > > *dev_priv, int size,
> > > - int fb_cpp)
> > > +/*
> > > + * For SKL+, the plane source size used by the hardware is based
> > > on the value we
> > > + * write to the PIPE_SIZE register. For BDW-, the hardware looks
> > > at the value we
> > > + * wrote to PIPESRC.
> > > + */
> > > +static void intel_fbc_get_plane_source_sizes(struct intel_crtc
> > > *crtc,
> > > + int *width, int
> > > *height)
> >
> > size in my mind already includes width and height, so plural _sizes
> > doesn't make much sense to me.
> >
> > > {
> > > + struct drm_i915_private *dev_priv = crtc->base.dev
> > > ->dev_private;
> > > + struct intel_plane_state *plane_state =
> > > + to_intel_plane_state(crtc->base.primary
> > > ->state);
> > > + int w, h;
> > > +
> > > + if (INTEL_INFO(dev_priv)->gen >= 9) {
> > > + if (intel_rotation_90_or_270(plane_state
> > > ->base.rotation)) {
> > > + w = drm_rect_height(&plane_state->src)
> > > >> 16;
> > > + h = drm_rect_width(&plane_state->src) >>
> > > 16;
> > > + } else {
> > > + w = drm_rect_width(&plane_state->src) >>
> > > 16;
> > > + h = drm_rect_height(&plane_state->src)
> > > >> 16;
> > > + }
> >
> > You can just use this same code for all platforms.

This code is trying to recalculate the values we use to write to
PIPESRC and PIPE_SIZE because that's what the HW is using. Since on the
older platforms we use crtc->pipe_src_x for PIPESRC, I think the
correct thing to do is to check those values.

> >
> > Actually I'm not sure what we should do wrt. rotation. Do we
> > support
> > FBC with 90/270 degree rotation? The scanout happens in a rotated
> > fashion, so swapping the dimensions like you do would seem like the
> > right thing. But not sure.
>
> While writing my reply tothe GTT tracking offset patch, I realized
> that
> 90/270 degree rotation requires Y-tiling, so since we're currently
> limiting FBC to X-tiling we can never get here with 90/270 degree
> rotation.

But SKL FBC does support Y tiling (even though our code doesn't), so
keeping the checks as they are would help preventing future problems.

>
> >
> > > + } else {
> > > + w = crtc->config->pipe_src_w;
> > > + h = crtc->config->pipe_src_h;
> > > + }
> > > +
> > > + if (width)
> > > + *width = w;
> > > + if (height)
> > > + *height = h;
> > > +}
> > > +
> > > +static int intel_fbc_calculate_cfb_size(struct intel_crtc *crtc)
> > > +{
> > > + struct drm_i915_private *dev_priv = crtc->base.dev
> > > ->dev_private;
> > > + struct drm_framebuffer *fb = crtc->base.primary->fb;
> > > + int lines;
> > > +
> > > + intel_fbc_get_plane_source_sizes(crtc, NULL, &lines);
> > > + if (INTEL_INFO(dev_priv)->gen >= 7)
> > > + lines = min(lines, 2048);
> > > +
> > > + return lines * fb->pitches[0];
> > > +}
> > > +
> > > +static int intel_fbc_setup_cfb(struct intel_crtc *crtc)
> > > +{
> > > + struct drm_i915_private *dev_priv = crtc->base.dev
> > > ->dev_private;
> > > + struct drm_framebuffer *fb = crtc->base.primary->fb;
> > > + int size, fb_cpp;
> > > +
> > > + size = intel_fbc_calculate_cfb_size(crtc);
> > > + fb_cpp = drm_format_plane_cpp(fb->pixel_format, 0);
> >
> > Can we just all it 'cpp' please. We already have too many names for
> > the

I was just moving things around...

> > same thing. Someone could also do a small search&replace to unify
> > the
> > whatever we have currently.

Someone could patch the drm_format_plane_cpp() function so that it at
least explains what CPP is supposed to mean in this context (Colors Per
Pixel? Countofbytes Per Pixel?). Or rename the function to
drm_format_pane_bpp() to make the name match the description.

> >
> > > +
> > > if (size <= dev_priv->fbc.uncompressed_size)
> > > return 0;
> > >
> > > @@ -897,8 +948,7 @@ static void __intel_fbc_update(struct
> > > drm_i915_private *dev_priv)
> > > goto out_disable;
> > > }
> > >
> > > - if (intel_fbc_setup_cfb(dev_priv, obj->base.size,
> > > - drm_format_plane_cpp(fb
> > > ->pixel_format, 0))) {
> > > + if (intel_fbc_setup_cfb(intel_crtc)) {
> > > set_no_fbc_reason(dev_priv,
> > > FBC_STOLEN_TOO_SMALL);
> > > goto out_disable;
> > > }
> > > --
> > > 2.5.3
> >
> > --
> > Ville Syrjälä
> > Intel OTC
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx