drm/i915/dsc/mtl: Enable alternate ICH method

DSC 1.2 is supported from MTL, hence program ICH accordingly.

Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220817124516.284456-2-jani.nikula@intel.com

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

@@ -597,6 +597,8 @@ static void intel_dsc_pps_configure(const struct intel_crtc_state *crtc_state)
 		DSC_VER_MIN_SHIFT |
 		vdsc_cfg->bits_per_component << DSC_BPC_SHIFT |
 		vdsc_cfg->line_buf_depth << DSC_LINE_BUF_DEPTH_SHIFT;
+	if (vdsc_cfg->dsc_version_minor == 2)
+		pps_val |= DSC_ALT_ICH_SEL;
 	if (vdsc_cfg->block_pred_enable)
 		pps_val |= DSC_BLOCK_PREDICTION;
 	if (vdsc_cfg->convert_rgb)

drivers/gpu/drm/i915/i915_reg.h

@@ -8003,6 +8003,7 @@ enum skl_power_gate {
 #define ICL_DSC1_PICTURE_PARAMETER_SET_0(pipe)	_MMIO_PIPE((pipe) - PIPE_B, \
 							   _ICL_DSC1_PICTURE_PARAMETER_SET_0_PB, \
 							   _ICL_DSC1_PICTURE_PARAMETER_SET_0_PC)
+#define  DSC_ALT_ICH_SEL		(1 << 20)
 #define  DSC_VBR_ENABLE			(1 << 19)
 #define  DSC_422_ENABLE			(1 << 18)
 #define  DSC_COLOR_SPACE_CONVERSION	(1 << 17)