drm/amdgpu: clear RB_OVERFLOW bit when enabling interrupts

Why:
Setting IH_RB_WPTR register to 0 will not clear the RB_OVERFLOW bit
if RB_ENABLE is not set.

How to fix:
Set WPTR_OVERFLOW_CLEAR bit after RB_ENABLE bit is set.
The RB_ENABLE bit is required to be set, together with
WPTR_OVERFLOW_ENABLE bit so that setting WPTR_OVERFLOW_CLEAR bit
would clear the RB_OVERFLOW.
Signed-off-by: Danijel Slivka <danijel.slivka@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/ih_v6_0.c

@@ -135,6 +135,34 @@ static int ih_v6_0_toggle_ring_interrupts(struct amdgpu_device *adev,
 
 	tmp = RREG32(ih_regs->ih_rb_cntl);
 	tmp = REG_SET_FIELD(tmp, IH_RB_CNTL, RB_ENABLE, (enable ? 1 : 0));
+
+	if (enable) {
+		/* Unset the CLEAR_OVERFLOW bit to make sure the next step
+		 * is switching the bit from 0 to 1
+		 */
+		tmp = REG_SET_FIELD(tmp, IH_RB_CNTL, WPTR_OVERFLOW_CLEAR, 0);
+		if (amdgpu_sriov_vf(adev) && amdgpu_sriov_reg_indirect_ih(adev)) {
+			if (psp_reg_program(&adev->psp, ih_regs->psp_reg_id, tmp))
+				return -ETIMEDOUT;
+		} else {
+			WREG32_NO_KIQ(ih_regs->ih_rb_cntl, tmp);
+		}
+
+		/* Clear RB_OVERFLOW bit */
+		tmp = REG_SET_FIELD(tmp, IH_RB_CNTL, WPTR_OVERFLOW_CLEAR, 1);
+		if (amdgpu_sriov_vf(adev) && amdgpu_sriov_reg_indirect_ih(adev)) {
+			if (psp_reg_program(&adev->psp, ih_regs->psp_reg_id, tmp))
+				return -ETIMEDOUT;
+		} else {
+			WREG32_NO_KIQ(ih_regs->ih_rb_cntl, tmp);
+		}
+
+		/* Unset the CLEAR_OVERFLOW bit immediately so new overflows
+		 * can be detected.
+		 */
+		tmp = REG_SET_FIELD(tmp, IH_RB_CNTL, WPTR_OVERFLOW_CLEAR, 0);
+	}
+
 	/* enable_intr field is only valid in ring0 */
 	if (ih == &adev->irq.ih)
 		tmp = REG_SET_FIELD(tmp, IH_RB_CNTL, ENABLE_INTR, (enable ? 1 : 0));