drm/i915/dsc: add basic hardware state readout support

Add basic hardware state readout for DSC, and check the most relevant
details in the state checker.

v2:
- check for DSC power before reading its state
- check if source supports DSC at all

As a side effect, this should also get the power domains for the enabled
DSC on takeover, and subsequently disable DSC if it's not needed.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3fb018cf9bd9a4c275aab389b6ec0f2a4e938bb9.1575974743.git.jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -4294,6 +4294,8 @@ void intel_ddi_get_config(struct intel_encoder *encoder,
 	if (WARN_ON(transcoder_is_dsi(cpu_transcoder)))
 		return;
 
+	intel_dsc_get_config(encoder, pipe_config);
+
 	temp = I915_READ(TRANS_DDI_FUNC_CTL(cpu_transcoder));
 	if (temp & TRANS_DDI_PHSYNC)
 		flags |= DRM_MODE_FLAG_PHSYNC;

drivers/gpu/drm/i915/display/intel_display.c

@@ -13301,6 +13301,10 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 	PIPE_CONF_CHECK_I(sync_mode_slaves_mask);
 	PIPE_CONF_CHECK_I(master_transcoder);
 
+	PIPE_CONF_CHECK_I(dsc.compression_enable);
+	PIPE_CONF_CHECK_I(dsc.dsc_split);
+	PIPE_CONF_CHECK_I(dsc.compressed_bpp);
+
 #undef PIPE_CONF_CHECK_X
 #undef PIPE_CONF_CHECK_I
 #undef PIPE_CONF_CHECK_BOOL

drivers/gpu/drm/i915/display/intel_vdsc.c

@@ -864,6 +864,55 @@ static void intel_dsc_pps_configure(struct intel_encoder *encoder,
 	}
 }
 
+void intel_dsc_get_config(struct intel_encoder *encoder,
+			  struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct drm_dsc_config *vdsc_cfg = &crtc_state->dsc.config;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+	enum pipe pipe = crtc->pipe;
+	enum intel_display_power_domain power_domain;
+	intel_wakeref_t wakeref;
+	u32 dss_ctl1, dss_ctl2, val;
+
+	if (!intel_dsc_source_support(encoder, crtc_state))
+		return;
+
+	power_domain = intel_dsc_power_domain(crtc_state);
+
+	wakeref = intel_display_power_get_if_enabled(dev_priv, power_domain);
+	if (!wakeref)
+		return;
+
+	if (crtc_state->cpu_transcoder == TRANSCODER_EDP) {
+		dss_ctl1 = I915_READ(DSS_CTL1);
+		dss_ctl2 = I915_READ(DSS_CTL2);
+	} else {
+		dss_ctl1 = I915_READ(ICL_PIPE_DSS_CTL1(pipe));
+		dss_ctl2 = I915_READ(ICL_PIPE_DSS_CTL2(pipe));
+	}
+
+	crtc_state->dsc.compression_enable = dss_ctl2 & LEFT_BRANCH_VDSC_ENABLE;
+	if (!crtc_state->dsc.compression_enable)
+		goto out;
+
+	crtc_state->dsc.dsc_split = (dss_ctl2 & RIGHT_BRANCH_VDSC_ENABLE) &&
+		(dss_ctl1 & JOINER_ENABLE);
+
+	/* FIXME: add more state readout as needed */
+
+	/* PPS1 */
+	if (cpu_transcoder == TRANSCODER_EDP)
+		val = I915_READ(DSCA_PICTURE_PARAMETER_SET_1);
+	else
+		val = I915_READ(ICL_DSC0_PICTURE_PARAMETER_SET_1(pipe));
+	vdsc_cfg->bits_per_pixel = val;
+	crtc_state->dsc.compressed_bpp = vdsc_cfg->bits_per_pixel >> 4;
+out:
+	intel_display_power_put(dev_priv, power_domain, wakeref);
+}
+
 static void intel_dsc_dsi_pps_write(struct intel_encoder *encoder,
 				    const struct intel_crtc_state *crtc_state)
 {

drivers/gpu/drm/i915/display/intel_vdsc.h

@@ -18,6 +18,8 @@ void intel_dsc_enable(struct intel_encoder *encoder,
 void intel_dsc_disable(const struct intel_crtc_state *crtc_state);
 int intel_dsc_compute_params(struct intel_encoder *encoder,
 			     struct intel_crtc_state *pipe_config);
+void intel_dsc_get_config(struct intel_encoder *encoder,
+			  struct intel_crtc_state *crtc_state);
 enum intel_display_power_domain
 intel_dsc_power_domain(const struct intel_crtc_state *crtc_state);