[PATCH] drm/amdgpu: Respect max pixel clock for HDMI and DVI-D

[Timur Kristóf]

Change the legacy (non-DC) display code to respect the maximum
pixel clock for HDMI and DVI-D. Reject modes that would require
a higher pixel clock than can be supported.

Also update the maximum supported HDMI clock value depending on
the ASIC type.

For reference, see the DC code:
check max_hdmi_pixel_clock in dce*_resource.c

Signed-off-by: Timur Kristóf <timur.kristof at gmail.com>
---
 .../gpu/drm/amd/amdgpu/amdgpu_connectors.c    | 21 +++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 5e375e9c4f5d..abcc4469cf57 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -1195,12 +1195,26 @@ static void amdgpu_connector_dvi_force(struct drm_connector *connector)
 		amdgpu_connector->use_digital = true;
 }
 
+/**
+ * Returns the maximum supported HDMI (TMDS) pixel clock in KHz.
+ */
+static int amdgpu_max_hdmi_pixel_clock(const struct amdgpu_device *adev)
+{
+	if (adev->asic_type >= CHIP_POLARIS10)
+		return 600000;
+	else if (adev->asic_type >= CHIP_TONGA)
+		return 300000;
+	else
+		return 297000;
+}
+
 static enum drm_mode_status amdgpu_connector_dvi_mode_valid(struct drm_connector *connector,
 					    const struct drm_display_mode *mode)
 {
 	struct drm_device *dev = connector->dev;
 	struct amdgpu_device *adev = drm_to_adev(dev);
 	struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(connector);
+	const int max_hdmi_pixel_clock = amdgpu_max_hdmi_pixel_clock(adev);
 
 	/* XXX check mode bandwidth */
 
@@ -1208,10 +1222,13 @@ static enum drm_mode_status amdgpu_connector_dvi_mode_valid(struct drm_connector
 		if ((amdgpu_connector->connector_object_id == CONNECTOR_OBJECT_ID_DUAL_LINK_DVI_I) ||
 		    (amdgpu_connector->connector_object_id == CONNECTOR_OBJECT_ID_DUAL_LINK_DVI_D) ||
 		    (amdgpu_connector->connector_object_id == CONNECTOR_OBJECT_ID_HDMI_TYPE_B)) {
-			return MODE_OK;
+			if (mode->clock > max_hdmi_pixel_clock)
+				return MODE_CLOCK_HIGH;
+			else
+				return MODE_OK;
 		} else if (connector->display_info.is_hdmi) {
 			/* HDMI 1.3+ supports max clock of 340 Mhz */
-			if (mode->clock > 340000)
+			if (mode->clock > max_hdmi_pixel_clock)
 				return MODE_CLOCK_HIGH;
 			else
 				return MODE_OK;
-- 
2.50.1