drm/i915: precompute pipe bpp before touching the hw

The procedure has now 3 steps:

1. Compute the bpp that the plane will output, this is done in
   pipe_config_set_bpp and stored into pipe_config->pipe_bpp. Also,
   this function clamps the pipe_bpp to whatever limit the EDID of any
   connected output specifies.
2. Adjust the pipe_bpp in the encoder and crtc functions, according to
   whatever constraints there are.
3. Decide whether to use dither by comparing the stored plane bpp with
   computed pipe_bpp.

There are a few slight functional changes in this patch:
- LVDS connector are now also going through the EDID clamping. But in
  a 2nd change we now unconditionally force the lvds bpc value - this
  shouldn't matter in reality when the panel setup is consistent, but
  better safe than sorry.
- HDMI now forces the pipe_bpp to the selected value - I think that's
  what we actually want, since otherwise at least the pixelclock
  computations are wrong (I'm not sure whether the port would accept
  e.g. 10 bpc when in 12bpc mode). Contrary to the old code, we pick
  the next higher bpc value, since otherwise there's no way to make
  use of the 12 bpc mode (since the next patch will remove the 12bpc
  plane format, it doesn't exist).

Both of these changes are due to the removal of the

	pipe_bpp = min(display_bpp, plane_bpp);

statement.

Another slight change is the reworking of the dp bpc code:
- For the mode_valid callback it's sufficient to only check whether
  the mode would fit at the lowest bpc.
- The bandwidth computation code is a bit restructured: It now walks
  all available bpp values in an outer loop and the codeblock that
  computes derived values (once a good configuration is found) has been
  moved out of the for loop maze. This is prep work to allow us to
  successively fall back on bpc values, and also correctly support bpc
  values != 8 or 6.

v2: Rebased on top of Paulo Zanoni's little refactoring to use more
drm dp helper functions.

v3: Rebased on top of Jani's eDP bpp fix and Ville's limited color
range work.

v4: Remove the INTEL_MODE_DP_FORCE_6BPC #define, no longer needed.

v5: Remove intel_crtc->bpp, too, and fix up the 12bpc check in the
hdmi code. Also fixup the bpp check in intel_dp.c, it'll get reworked
in a later patch though again.

v6: Fix spelling in a comment.

v7: Debug output improvements for the bpp computation.

v8: Fixup 6bpc lvds check - dual-link and 8bpc mode are different
things!

v9: Reinstate the fix to properly ignore the firmware edp bpp ... this
was lost in a rebase.

v10: Both g4x and vlv lack 12bpc pipes, so don't enforce that we have
that. Still unsure whether this is the way to go, but at least 6bpc
for a 8bpc hdmi output seems to work.

v11: And g4x/vlv also lack 12bpc hdmi support, so only support high
depth on DP. Adjust the code.

v12: Rebased.

v13: Split out the introduction of pipe_config->dither|pipe_bpp, as
requested from Jesse Barnes.

v14: Split out the special 6BPC handling for DP, as requested by Jesse
Barnes.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

4 files changed, 100 insertions, 156 deletions

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 3d09df0d4b9d..6c6b0124f17d 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -945,9 +945,7 @@ void intel_ddi_set_pipe_settings(struct drm_crtc *crtc)
                         temp |= TRANS_MSA_12_BPC;
                         break;
                 default:
-                        temp |= TRANS_MSA_8_BPC;
-                        WARN(1, "%d bpp unsupported by DDI function\n",
-                             intel_crtc->config.pipe_bpp);
+                        BUG();
                 }
                 I915_WRITE(TRANS_MSA_MISC(cpu_transcoder), temp);
         }
@@ -983,8 +981,7 @@ void intel_ddi_enable_transcoder_func(struct drm_crtc *crtc)
                 temp |= TRANS_DDI_BPC_12;
                 break;
         default:
-                WARN(1, "%d bpp unsupported by transcoder DDI function\n",
-                     intel_crtc->config.pipe_bpp);
+                BUG();
         }
 
         if (crtc->mode.flags & DRM_MODE_FLAG_PVSYNC)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4cc46ef9ca9f..14397726d3ac 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4076,142 +4076,6 @@ static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
                 && !(dev_priv->quirks & QUIRK_LVDS_SSC_DISABLE);
 }
 
-/**
- * intel_choose_pipe_bpp_dither - figure out what color depth the pipe should send
- * @crtc: CRTC structure
- * @mode: requested mode
- *
- * A pipe may be connected to one or more outputs.  Based on the depth of the
- * attached framebuffer, choose a good color depth to use on the pipe.
- *
- * If possible, match the pipe depth to the fb depth.  In some cases, this
- * isn't ideal, because the connected output supports a lesser or restricted
- * set of depths.  Resolve that here:
- *    LVDS typically supports only 6bpc, so clamp down in that case
- *    HDMI supports only 8bpc or 12bpc, so clamp to 8bpc with dither for 10bpc
- *    Displays may support a restricted set as well, check EDID and clamp as
- *      appropriate.
- *    DP may want to dither down to 6bpc to fit larger modes
- *
- * RETURNS:
- * Dithering requirement (i.e. false if display bpc and pipe bpc match,
- * true if they don't match).
- */
-static bool intel_choose_pipe_bpp_dither(struct drm_crtc *crtc,
-                                         struct drm_framebuffer *fb,
-                                         unsigned int *pipe_bpp,
-                                         struct drm_display_mode *mode)
-{
-        struct drm_device *dev = crtc->dev;
-        struct drm_i915_private *dev_priv = dev->dev_private;
-        struct drm_connector *connector;
-        struct intel_encoder *intel_encoder;
-        unsigned int display_bpc = UINT_MAX, bpc;
-
-        /* Walk the encoders & connectors on this crtc, get min bpc */
-        for_each_encoder_on_crtc(dev, crtc, intel_encoder) {
-
-                if (intel_encoder->type == INTEL_OUTPUT_LVDS) {
-                        unsigned int lvds_bpc;
-
-                        if ((I915_READ(PCH_LVDS) & LVDS_A3_POWER_MASK) ==
-                            LVDS_A3_POWER_UP)
-                                lvds_bpc = 8;
-                        else
-                                lvds_bpc = 6;
-
-                        if (lvds_bpc < display_bpc) {
-                                DRM_DEBUG_KMS("clamping display bpc (was %d) to LVDS (%d)\n", display_bpc, lvds_bpc);
-                                display_bpc = lvds_bpc;
-                        }
-                        continue;
-                }
-
-                /* Not one of the known troublemakers, check the EDID */
-                list_for_each_entry(connector, &dev->mode_config.connector_list,
-                                    head) {
-                        if (connector->encoder != &intel_encoder->base)
-                                continue;
-
-                        /* Don't use an invalid EDID bpc value */
-                        if (connector->display_info.bpc &&
-                            connector->display_info.bpc < display_bpc) {
-                                DRM_DEBUG_KMS("clamping display bpc (was %d) to EDID reported max of %d\n", display_bpc, connector->display_info.bpc);
-                                display_bpc = connector->display_info.bpc;
-                        }
-                }
-
-                if (intel_encoder->type == INTEL_OUTPUT_EDP) {
-                        /* Use VBT settings if we have an eDP panel */
-                        unsigned int edp_bpc = dev_priv->edp.bpp / 3;
-
-                        if (edp_bpc && edp_bpc < display_bpc) {
-                                DRM_DEBUG_KMS("clamping display bpc (was %d) to eDP (%d)\n", display_bpc, edp_bpc);
-                                display_bpc = edp_bpc;
-                        }
-                        continue;
-                }
-
-                /*
-                 * HDMI is either 12 or 8, so if the display lets 10bpc sneak
-                 * through, clamp it down.  (Note: >12bpc will be caught below.)
-                 */
-                if (intel_encoder->type == INTEL_OUTPUT_HDMI) {
-                        if (display_bpc > 8 && display_bpc < 12) {
-                                DRM_DEBUG_KMS("forcing bpc to 12 for HDMI\n");
-                                display_bpc = 12;
-                        } else {
-                                DRM_DEBUG_KMS("forcing bpc to 8 for HDMI\n");
-                                display_bpc = 8;
-                        }
-                }
-        }
-
-        if (mode->private_flags & INTEL_MODE_DP_FORCE_6BPC) {
-                DRM_DEBUG_KMS("Dithering DP to 6bpc\n");
-                display_bpc = 6;
-        }
-
-        /*
-         * We could just drive the pipe at the highest bpc all the time and
-         * enable dithering as needed, but that costs bandwidth.  So choose
-         * the minimum value that expresses the full color range of the fb but
-         * also stays within the max display bpc discovered above.
-         */
-
-        switch (fb->depth) {
-        case 8:
-                bpc = 8; /* since we go through a colormap */
-                break;
-        case 15:
-        case 16:
-                bpc = 6; /* min is 18bpp */
-                break;
-        case 24:
-                bpc = 8;
-                break;
-        case 30:
-                bpc = 10;
-                break;
-        case 48:
-                bpc = 12;
-                break;
-        default:
-                DRM_DEBUG("unsupported depth, assuming 24 bits\n");
-                bpc = min((unsigned int)8, display_bpc);
-                break;
-        }
-
-        display_bpc = min(display_bpc, bpc);
-
-        DRM_DEBUG_KMS("setting pipe bpc to %d (max display bpc %d)\n",
-                      bpc, display_bpc);
-
-        *pipe_bpp = display_bpc * 3;
-
-        return display_bpc != bpc;
-}
-
 static int vlv_get_refclk(struct drm_crtc *crtc)
 {
         struct drm_device *dev = crtc->dev;
@@ -4665,10 +4529,6 @@ static int i9xx_crtc_mode_set(struct drm_crtc *crtc,
         const intel_limit_t *limit;
         int ret;
 
-        /* temporary hack */
-        intel_crtc->config.dither =
-                adjusted_mode->private_flags & INTEL_MODE_DP_FORCE_6BPC;
-
         for_each_encoder_on_crtc(dev, crtc, encoder) {
                 switch (encoder->type) {
                 case INTEL_OUTPUT_LVDS:
@@ -5673,10 +5533,7 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
         intel_crtc_update_cursor(crtc, true);
 
         /* determine panel color depth */
-        dither = intel_choose_pipe_bpp_dither(crtc, fb,
-                                              &intel_crtc->config.pipe_bpp,
-                                              adjusted_mode);
-        intel_crtc->config.dither = dither;
+        dither = intel_crtc->config.dither;
         if (is_lvds && dev_priv->lvds_dither)
                 dither = true;
 
@@ -5841,10 +5698,7 @@ static int haswell_crtc_mode_set(struct drm_crtc *crtc,
         intel_crtc_update_cursor(crtc, true);
 
         /* determine panel color depth */
-        dither = intel_choose_pipe_bpp_dither(crtc, fb,
-                                              &intel_crtc->config.pipe_bpp,
-                                              adjusted_mode);
-        intel_crtc->config.dither = dither;
+        dither = intel_crtc->config.dither;
 
         DRM_DEBUG_KMS("Mode for pipe %d:\n", pipe);
         drm_mode_debug_printmodeline(mode);
@@ -7525,14 +7379,72 @@ static void intel_modeset_commit_output_state(struct drm_device *dev)
         }
 }
 
+static int
+pipe_config_set_bpp(struct drm_crtc *crtc,
+                    struct drm_framebuffer *fb,
+                    struct intel_crtc_config *pipe_config)
+{
+        struct drm_device *dev = crtc->dev;
+        struct drm_connector *connector;
+        int bpp;
+
+        switch (fb->depth) {
+        case 8:
+                bpp = 8*3; /* since we go through a colormap */
+                break;
+        case 15:
+        case 16:
+                bpp = 6*3; /* min is 18bpp */
+                break;
+        case 24:
+                bpp = 8*3;
+                break;
+        case 30:
+                bpp = 10*3;
+                break;
+        case 48:
+                bpp = 12*3;
+                break;
+        default:
+                DRM_DEBUG_KMS("unsupported depth\n");
+                return -EINVAL;
+        }
+
+        if (fb->depth > 24 && !HAS_PCH_SPLIT(dev)) {
+                DRM_DEBUG_KMS("high depth not supported on gmch platforms\n");
+                return -EINVAL;
+        }
+
+        pipe_config->pipe_bpp = bpp;
+
+        /* Clamp display bpp to EDID value */
+        list_for_each_entry(connector, &dev->mode_config.connector_list,
+                            head) {
+                if (connector->encoder && connector->encoder->crtc != crtc)
+                        continue;
+
+                /* Don't use an invalid EDID bpc value */
+                if (connector->display_info.bpc &&
+                    connector->display_info.bpc * 3 < bpp) {
+                        DRM_DEBUG_KMS("clamping display bpp (was %d) to EDID reported max of %d\n",
+                                      bpp, connector->display_info.bpc*3);
+                        pipe_config->pipe_bpp = connector->display_info.bpc*3;
+                }
+        }
+
+        return bpp;
+}
+
 static struct intel_crtc_config *
 intel_modeset_pipe_config(struct drm_crtc *crtc,
+                          struct drm_framebuffer *fb,
                           struct drm_display_mode *mode)
 {
         struct drm_device *dev = crtc->dev;
         struct drm_encoder_helper_funcs *encoder_funcs;
         struct intel_encoder *encoder;
         struct intel_crtc_config *pipe_config;
+        int plane_bpp;
 
         pipe_config = kzalloc(sizeof(*pipe_config), GFP_KERNEL);
         if (!pipe_config)
@@ -7541,6 +7453,10 @@ intel_modeset_pipe_config(struct drm_crtc *crtc,
         drm_mode_copy(&pipe_config->adjusted_mode, mode);
         drm_mode_copy(&pipe_config->requested_mode, mode);
 
+        plane_bpp = pipe_config_set_bpp(crtc, fb, pipe_config);
+        if (plane_bpp < 0)
+                goto fail;
+
         /* Pass our mode to the connectors and the CRTC to give them a chance to
          * adjust it according to limitations or connector properties, and also
          * a chance to reject the mode entirely.
@@ -7569,12 +7485,20 @@ intel_modeset_pipe_config(struct drm_crtc *crtc,
                 }
         }
 
+        /* temporary hack until the DP code doesn't use the 6BPC flag any more */
+        if (pipe_config->adjusted_mode.private_flags & INTEL_MODE_DP_FORCE_6BPC)
+                pipe_config->pipe_bpp = 6*8;
+
         if (!(intel_crtc_compute_config(crtc, pipe_config))) {
                 DRM_DEBUG_KMS("CRTC fixup failed\n");
                 goto fail;
         }
         DRM_DEBUG_KMS("[CRTC:%d]\n", crtc->base.id);
 
+        pipe_config->dither = pipe_config->pipe_bpp != plane_bpp;
+        DRM_DEBUG_KMS("plane bpp: %i, pipe bpp: %i, dithering: %i\n",
+                      plane_bpp, pipe_config->pipe_bpp, pipe_config->dither);
+
         return pipe_config;
 fail:
         kfree(pipe_config);
@@ -7866,7 +7790,7 @@ int intel_set_mode(struct drm_crtc *crtc,
          * pieces of code that are not yet converted to deal with mutliple crtcs
          * changing their mode at the same time. */
         if (modeset_pipes) {
-                pipe_config = intel_modeset_pipe_config(crtc, mode);
+                pipe_config = intel_modeset_pipe_config(crtc, fb, mode);
                 if (IS_ERR(pipe_config)) {
                         ret = PTR_ERR(pipe_config);
                         pipe_config = NULL;
@@ -8305,8 +8229,6 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
         dev_priv->plane_to_crtc_mapping[intel_crtc->plane] = &intel_crtc->base;
         dev_priv->pipe_to_crtc_mapping[intel_crtc->pipe] = &intel_crtc->base;
 
-        intel_crtc->config.pipe_bpp = 24; /* default for pre-Ironlake */
-
         drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 0731ba660aac..b206a0db7716 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -791,6 +791,19 @@ bool intel_hdmi_compute_config(struct intel_encoder *encoder,
         if (HAS_PCH_SPLIT(dev) && !HAS_DDI(dev))
                 pipe_config->has_pch_encoder = true;
 
+        /*
+         * HDMI is either 12 or 8, so if the display lets 10bpc sneak
+         * through, clamp it down. Note that g4x/vlv don't support 12bpc hdmi
+         * outputs.
+         */
+        if (pipe_config->pipe_bpp > 8*3 && HAS_PCH_SPLIT(dev)) {
+                DRM_DEBUG_KMS("forcing bpc to 12 for HDMI\n");
+                pipe_config->pipe_bpp = 12*3;
+        } else {
+                DRM_DEBUG_KMS("forcing bpc to 8 for HDMI\n");
+                pipe_config->pipe_bpp = 8*3;
+        }
+
         return true;
 }
 
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 9d6ed91b443d..7b6d07b6a02d 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -310,6 +310,7 @@ static bool intel_lvds_compute_config(struct intel_encoder *intel_encoder,
         struct drm_display_mode *mode = &pipe_config->requested_mode;
         struct intel_crtc *intel_crtc = lvds_encoder->base.new_crtc;
         u32 pfit_control = 0, pfit_pgm_ratios = 0, border = 0;
+        unsigned int lvds_bpp;
         int pipe;
 
         /* Should never happen!! */
@@ -321,6 +322,17 @@ static bool intel_lvds_compute_config(struct intel_encoder *intel_encoder,
         if (intel_encoder_check_is_cloned(&lvds_encoder->base))
                 return false;
 
+        if ((I915_READ(lvds_encoder->reg) & LVDS_A3_POWER_MASK) ==
+            LVDS_A3_POWER_UP)
+                lvds_bpp = 8*3;
+        else
+                lvds_bpp = 6*3;
+
+        if (lvds_bpp != pipe_config->pipe_bpp) {
+                DRM_DEBUG_KMS("forcing display bpp (was %d) to LVDS (%d)\n",
+                              pipe_config->pipe_bpp, lvds_bpp);
+                pipe_config->pipe_bpp = lvds_bpp;
+        }
         /*
          * We have timings from the BIOS for the panel, put them in
          * to the adjusted mode.  The CRTC will be set up for this mode,