drm/radeon/kms: fix up DP clock programming on DCE4/5

In DP mode, the DP ref clock can come from PPLL, DCPLL, or ext clock,
depending on the asic.  The crtc virtual pixel clock is derived from
the DP ref clock.

- DCE4: PPLL or ext clock
- DCE5: DCPLL or ext clock

Setting ATOM_PPLL_INVALID will cause SetPixelClock to skip
PPLL/DCPLL programming and only program the DP DTO for the
crtc virtual pixel clock.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 18 insertions, 5 deletions

diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
index ff0d1cad1012..9770afff4d4c 100644
--- a/drivers/gpu/drm/radeon/atombios_crtc.c
+++ b/drivers/gpu/drm/radeon/atombios_crtc.c
@@ -1443,11 +1443,19 @@ static int radeon_atom_pick_pll(struct drm_crtc *crtc)
         uint32_t pll_in_use = 0;
 
         if (ASIC_IS_DCE4(rdev)) {
-                /* if crtc is driving DP and we have an ext clock, use that */
                 list_for_each_entry(test_encoder, &dev->mode_config.encoder_list, head) {
                         if (test_encoder->crtc && (test_encoder->crtc == crtc)) {
+                                /* in DP mode, the DP ref clock can come from PPLL, DCPLL, or ext clock,
+                                 * depending on the asic:
+                                 * DCE4: PPLL or ext clock
+                                 * DCE5: DCPLL or ext clock
+                                 *
+                                 * Setting ATOM_PPLL_INVALID will cause SetPixelClock to skip
+                                 * PPLL/DCPLL programming and only program the DP DTO for the
+                                 * crtc virtual pixel clock.
+                                 */
                                 if (atombios_get_encoder_mode(test_encoder) == ATOM_ENCODER_MODE_DP) {
-                                        if (rdev->clock.dp_extclk)
+                                        if (ASIC_IS_DCE5(rdev) || rdev->clock.dp_extclk)
                                                 return ATOM_PPLL_INVALID;
                                 }
                         }
diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 6c6793e6e3a5..4d66e249e1c1 100644
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -988,11 +988,16 @@ atombios_dig_transmitter_setup(struct drm_encoder *encoder, int action, uint8_t
                 }
 
                 if (ASIC_IS_DCE5(rdev)) {
-                        if (is_dp && rdev->clock.dp_extclk)
-                                args.v4.acConfig.ucRefClkSource = 3; /* external src */
-                        else
+                        /* On DCE5 DCPLL usually generates the DP ref clock */
+                        if (is_dp) {
+                                if (rdev->clock.dp_extclk)
+                                        args.v4.acConfig.ucRefClkSource = ENCODER_REFCLK_SRC_EXTCLK;
+                                else
+                                        args.v4.acConfig.ucRefClkSource = ENCODER_REFCLK_SRC_DCPLL;
+                        } else
                                 args.v4.acConfig.ucRefClkSource = pll_id;
                 } else {
+                        /* On DCE4, if there is an external clock, it generates the DP ref clock */
                         if (is_dp && rdev->clock.dp_extclk)
                                 args.v3.acConfig.ucRefClkSource = 2; /* external src */
                         else