drm/radeon: avoid turning off spread spectrum for used pll

If spread spectrum is enabled and in use for a given pll we
should not turn it off as it will lead to turning off display
for crtc that use the pll (this behavior was observed on chelsea
edp).
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -444,11 +444,28 @@ union atom_enable_ss {
 static void atombios_crtc_program_ss(struct radeon_device *rdev,
 				     int enable,
 				     int pll_id,
+				     int crtc_id,
 				     struct radeon_atom_ss *ss)
 {
+	unsigned i;
 	int index = GetIndexIntoMasterTable(COMMAND, EnableSpreadSpectrumOnPPLL);
 	union atom_enable_ss args;
 
+	if (!enable) {
+		for (i = 0; i < 6; i++) {
+			if (rdev->mode_info.crtcs[i] &&
+			    rdev->mode_info.crtcs[i]->enabled &&
+			    i != crtc_id &&
+			    pll_id == rdev->mode_info.crtcs[i]->pll_id) {
+				/* one other crtc is using this pll don't turn
+				 * off spread spectrum as it might turn off
+				 * display on active crtc
+				 */
+				return;
+			}
+		}
+	}
+
 	memset(&args, 0, sizeof(args));
 
 	if (ASIC_IS_DCE5(rdev)) {
@@ -1028,7 +1045,7 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
 		radeon_compute_pll_legacy(pll, adjusted_clock, &pll_clock, &fb_div, &frac_fb_div,
 					  &ref_div, &post_div);
 
-	atombios_crtc_program_ss(rdev, ATOM_DISABLE, radeon_crtc->pll_id, &ss);
+	atombios_crtc_program_ss(rdev, ATOM_DISABLE, radeon_crtc->pll_id, radeon_crtc->crtc_id, &ss);
 
 	atombios_crtc_program_pll(crtc, radeon_crtc->crtc_id, radeon_crtc->pll_id,
 				  encoder_mode, radeon_encoder->encoder_id, mode->clock,
@@ -1051,7 +1068,7 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
 			ss.step = step_size;
 		}
 
-		atombios_crtc_program_ss(rdev, ATOM_ENABLE, radeon_crtc->pll_id, &ss);
+		atombios_crtc_program_ss(rdev, ATOM_ENABLE, radeon_crtc->pll_id, radeon_crtc->crtc_id, &ss);
 	}
 }
 
@@ -1572,11 +1589,11 @@ void radeon_atom_disp_eng_pll_init(struct radeon_device *rdev)
 								   ASIC_INTERNAL_SS_ON_DCPLL,
 								   rdev->clock.default_dispclk);
 		if (ss_enabled)
-			atombios_crtc_program_ss(rdev, ATOM_DISABLE, ATOM_DCPLL, &ss);
+			atombios_crtc_program_ss(rdev, ATOM_DISABLE, ATOM_DCPLL, -1, &ss);
 		/* XXX: DCE5, make sure voltage, dispclk is high enough */
 		atombios_crtc_set_disp_eng_pll(rdev, rdev->clock.default_dispclk);
 		if (ss_enabled)
-			atombios_crtc_program_ss(rdev, ATOM_ENABLE, ATOM_DCPLL, &ss);
+			atombios_crtc_program_ss(rdev, ATOM_ENABLE, ATOM_DCPLL, -1, &ss);
 	}
 
 }