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SubjectRe: [PATCH] drm/amdgpu: Add 'modeset' module parameter
From
Hi

Am 11.05.22 um 20:19 schrieb Lyude Paul:
> Many DRM drivers feature a 'modeset' argument, which can be used to
> enable/disable the entire driver (as opposed to passing nomodeset to the
> kernel, which would disable modesetting globally and make it difficult to
> load amdgpu afterwards). Apparently amdgpu is actually missing this
> however, so let's add it!

We have recently consolidated the handling of the modeset parameter in
the macro drm_module_pci_driver_if_modeset(), [1] which has a
deprecation warning in the docs. Only a few older drivers use modeset
and we don't want to use it further.

Better alternatives are nomodeset or initcall_blacklist=amdgpu_init.

Best regards
Thomas

[1]
https://cgit.freedesktop.org/drm/drm-tip/tree/include/drm/drm_module.h#n79

>
> Keep in mind that this currently just lets one enable or disable amdgpu, I
> haven't bothered adding a headless mode like nouveau has - however I'm sure
> someone else can add this if needed.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index ebd37fb19cdb..24e6fb4517cc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -872,6 +872,15 @@ MODULE_PARM_DESC(smu_pptable_id,
> "specify pptable id to be used (-1 = auto(default) value, 0 = use pptable from vbios, > 0 = soft pptable id)");
> module_param_named(smu_pptable_id, amdgpu_smu_pptable_id, int, 0444);
>
> +/**
> + * DOC: modeset (int)
> + * Used to enable/disable modesetting for amdgpu exclusively.
> + */
> +bool amdgpu_enable_modeset = true;
> +MODULE_PARM_DESC(modeset,
> + "Enable or disable display driver (1 = on (default), 0 = off");
> +module_param_named(modeset, amdgpu_enable_modeset, bool, 0444);
> +
> /* These devices are not supported by amdgpu.
> * They are supported by the mach64, r128, radeon drivers
> */
> @@ -2003,6 +2012,11 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
> bool is_fw_fb;
> resource_size_t base, size;
>
> + if (!amdgpu_enable_modeset) {
> + DRM_INFO("modeset=0 passed to amdgpu, driver will not be enabled\n");
> + return -ENODEV;
> + }
> +
> /* skip devices which are owned by radeon */
> for (i = 0; i < ARRAY_SIZE(amdgpu_unsupported_pciidlist); i++) {
> if (amdgpu_unsupported_pciidlist[i] == pdev->device)

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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