drm/i915/gvt: Handle EDP_PSR_IMR and EDP_PSR_IIR for BXT.

BXT supports EDP. However since GVT-g only simulate DP monitor
to guest and handles EDP_PSR_IMR and EDP_PSR_IIR as default MMIO
r/w. If guest r/w these IMR/IIR, GVT-g won't simulate the real
HW behavior and below warning is printed:
--------
Interrupt register 0x64838 is not zero: 0xffffffff
WARNING: CPU: 1 PID: 1 at drivers/gpu/drm/i915/i915_irq.c:161
gen3_assert_iir_is_zero+0x34/0xa0

Call Trace:
gen8_de_irq_postinstall+0xad/0x330
gen8_irq_postinstall+0x23/0x80
drm_irq_install+0xb5/0x130
i915_driver_load+0xafd/0xf70
--------
Since GVT-g won't simulate EDP to guest, always set EDP_PSR_IMR
and EDP_PSR_IIR IMR/IIR to 0.
Signed-off-by: Colin Xu <colin.xu@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/handlers.c

@@ -1584,6 +1584,13 @@ static int bxt_gt_disp_pwron_write(struct intel_vgpu *vgpu,
 	return 0;
 }
 
+static int bxt_edp_psr_imr_iir_write(struct intel_vgpu *vgpu,
+		unsigned int offset, void *p_data, unsigned int bytes)
+{
+	vgpu_vreg(vgpu, offset) = 0;
+	return 0;
+}
+
 static int mmio_read_from_hw(struct intel_vgpu *vgpu,
 		unsigned int offset, void *p_data, unsigned int bytes)
 {
@@ -3182,6 +3189,9 @@ static int init_bxt_mmio_info(struct intel_gvt *gvt)
 	MMIO_D(HSW_TVIDEO_DIP_GCP(TRANSCODER_B), D_BXT);
 	MMIO_D(HSW_TVIDEO_DIP_GCP(TRANSCODER_C), D_BXT);
 
+	MMIO_DH(EDP_PSR_IMR, D_BXT, NULL, bxt_edp_psr_imr_iir_write);
+	MMIO_DH(EDP_PSR_IIR, D_BXT, NULL, bxt_edp_psr_imr_iir_write);
+
 	MMIO_D(RC6_CTX_BASE, D_BXT);
 
 	MMIO_D(GEN8_PUSHBUS_CONTROL, D_BXT);