drm/i915: Fix pipe_bpp readout for BXT/GLK DSI

The only bpc information in pipe registers for BXT/GLK DSI
is the PIPEMISC dither bpc. Let's try to use that to read
out pipe_bpp on these platforms. However, I'm not sure if
this will be correctly populated by the GOP since bspec
suggests it's only needed if dithering is actually enabled.
If not I guess we'll have to go one step further and
extract pipe_bpp from the DSI pixel format when dithering
is disabled.

Cc: Hans de Goede <hdegoede@redhat.com>
Fixes: ca0b04db14a5 ("drm/i915/dsi: Fix pipe_bpp for handling for 6 bpc pixel-formats")
References: https://bugs.freedesktop.org/show_bug.cgi?id=109516
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190405141349.11950-1-ville.syrjala@linux.intel.com
(cherry picked from commit 499653501baf27d26e73cb5ce744869df3400509)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/i915/vlv_dsi.c b/drivers/gpu/drm/i915/vlv_dsi.c
index 6403728..31c93c3 100644 (file)
--- a/drivers/gpu/drm/i915/vlv_dsi.c
+++ b/drivers/gpu/drm/i915/vlv_dsi.c
@@ -256,6 +256,28 @@ static void band_gap_reset(struct drm_i915_private *dev_priv)
        mutex_unlock(&dev_priv->sb_lock);
 }
 
+static int bdw_get_pipemisc_bpp(struct intel_crtc *crtc)
+{
+       struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+       u32 tmp;
+
+       tmp = I915_READ(PIPEMISC(crtc->pipe));
+
+       switch (tmp & PIPEMISC_DITHER_BPC_MASK) {
+       case PIPEMISC_DITHER_6_BPC:
+               return 18;
+       case PIPEMISC_DITHER_8_BPC:
+               return 24;
+       case PIPEMISC_DITHER_10_BPC:
+               return 30;
+       case PIPEMISC_DITHER_12_BPC:
+               return 36;
+       default:
+               MISSING_CASE(tmp);
+               return 0;
+       }
+}
+
 static int intel_dsi_compute_config(struct intel_encoder *encoder,
                                    struct intel_crtc_state *pipe_config,
                                    struct drm_connector_state *conn_state)
@@ -1071,6 +1093,8 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
        bpp = mipi_dsi_pixel_format_to_bpp(
                        pixel_format_from_register_bits(fmt));
 
+       pipe_config->pipe_bpp = bdw_get_pipemisc_bpp(crtc);
+
        /* Enable Frame time stamo based scanline reporting */
        adjusted_mode->private_flags |=
                        I915_MODE_FLAG_GET_SCANLINE_FROM_TIMESTAMP;