On Thu, Mar 6, 2025 at 1:58 PM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
>
> Modern APU and dGPU require DC support to be able to light up the
> display. If DC support has been disabled either by kernel config
> or by kernel command line the screen will visibly freeze when the
> driver finishes early init.
>
> As it's known before early init is done whether DC support is required
> detect this during discovery and bail if DC support was disabled
> for any reason. This will ensure that the existing framebuffer
> provided by efifb or simpledrm keeps working.
I think there are a couple of corner cases we need to handle:
1. if adev->enable_virtual_display is set. The user has configured
virtual displays and hence they want to use them rather than the
actual physical displays. This is useful with GPUs in servers or for
early bring up.
2. If the board supports DCN IP, but all it's been fused off due to
silicon flaws (e.g., adev->harvest_ip_mask & AMD_HARVEST_IP_DMU_MASK).
In that case, we don't want to fail.
Alex
>
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> v2:
> * Update commit message justification
> * Add correct "default" handling
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 46 +++++++++++++------
> 1 file changed, 33 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> index a4258127083d..24f532de6322 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> @@ -2139,10 +2139,6 @@ static int amdgpu_discovery_set_display_ip_blocks(struct amdgpu_device *adev)
> return 0;
> }
>
> - if (!amdgpu_device_has_dc_support(adev))
> - return 0;
> -
> -#if defined(CONFIG_DRM_AMD_DC)
> if (amdgpu_ip_version(adev, DCE_HWIP, 0)) {
> switch (amdgpu_ip_version(adev, DCE_HWIP, 0)) {
> case IP_VERSION(1, 0, 0):
> @@ -2166,39 +2162,63 @@ static int amdgpu_discovery_set_display_ip_blocks(struct amdgpu_device *adev)
> case IP_VERSION(3, 5, 1):
> case IP_VERSION(3, 6, 0):
> case IP_VERSION(4, 1, 0):
> + if (!amdgpu_device_has_dc_support(adev)) {
> + dev_err(adev->dev,
> + "DC support is required for dm ip block(DCE_HWIP:0x%x)\n",
> + amdgpu_ip_version(adev, DCE_HWIP, 0));
> + return -EINVAL;
> + }
> +
> /* TODO: Fix IP version. DC code expects version 4.0.1 */
> if (adev->ip_versions[DCE_HWIP][0] == IP_VERSION(4, 1, 0))
> adev->ip_versions[DCE_HWIP][0] = IP_VERSION(4, 0, 1);
>
> +#if defined(CONFIG_DRM_AMD_DC)
> if (amdgpu_sriov_vf(adev))
> amdgpu_discovery_set_sriov_display(adev);
> else
> amdgpu_device_ip_block_add(adev, &dm_ip_block);
> break;
> +#endif
> default:
> - dev_err(adev->dev,
> - "Failed to add dm ip block(DCE_HWIP:0x%x)\n",
> - amdgpu_ip_version(adev, DCE_HWIP, 0));
> - return -EINVAL;
> + if (amdgpu_device_has_dc_support(adev)) {
> + dev_err(adev->dev,
> + "Failed to add dm ip block(DCE_HWIP:0x%x)\n",
> + amdgpu_ip_version(adev, DCE_HWIP, 0));
> + return -EINVAL;
> + }
> + return 0;
> }
> } else if (amdgpu_ip_version(adev, DCI_HWIP, 0)) {
> switch (amdgpu_ip_version(adev, DCI_HWIP, 0)) {
> case IP_VERSION(12, 0, 0):
> case IP_VERSION(12, 0, 1):
> case IP_VERSION(12, 1, 0):
> +
> + if (!amdgpu_device_has_dc_support(adev)) {
> + dev_err(adev->dev,
> + "DC support is required for dm ip block(DCI_HWIP:0x%x)\n",
> + amdgpu_ip_version(adev, DCI_HWIP, 0));
> + return -EINVAL;
> + }
> +
> +#if defined(CONFIG_DRM_AMD_DC)
> if (amdgpu_sriov_vf(adev))
> amdgpu_discovery_set_sriov_display(adev);
> else
> amdgpu_device_ip_block_add(adev, &dm_ip_block);
> break;
> +#endif
> default:
> - dev_err(adev->dev,
> - "Failed to add dm ip block(DCI_HWIP:0x%x)\n",
> - amdgpu_ip_version(adev, DCI_HWIP, 0));
> - return -EINVAL;
> + if (amdgpu_device_has_dc_support(adev)) {
> + dev_err(adev->dev,
> + "Failed to add dm ip block(DCI_HWIP:0x%x)\n",
> + amdgpu_ip_version(adev, DCI_HWIP, 0));
> + return -EINVAL;
> + }
> + return 0;
> }
> }
> -#endif
> return 0;
> }
>
> --
> 2.48.1
>
