On Mon, Aug 25, 2025 at 6:10 PM Timur Kristóf <timur.kris...@gmail.com> wrote:
>
> 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.kris...@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;
I don't think it makes sense to limit dual link DVI to the max HDMI
clock. HDMI is single link TMDS. Other than that, the patch looks
good to me.
Alex
> } 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
>
