[PATCH] drm/amdgpu: fix check in fbdev init

[Alex Deucher]

On Tue, Jul 19, 2022 at 2:57 PM Alex Deucher <alexander.deucher at amd.com> wrote:
>
> The new vkms virtual display code is atomic so there is
> no need to call drm_helper_disable_unused_functions()
> when it is enabled.  Doing so can result in a segfault.
> When the driver switched from the old virtual display code
> to the new atomic virtual display code, it was missed that
> we enable virtual display unconditionally under SR-IOV
> so the checks here missed that case.  Add the missing
> check for SR-IOV.
>
> There is no equivalent of this patch for Linus' tree
> because the relevant code no longer exists.  This patch
> is only relevant to kernels 5.15 and 5.16.
>
> Fixes: 84ec374bd580 ("drm/amdgpu: create amdgpu_vkms (v4)")
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> Cc: stable at vger.kernel.org # 5.15.x
> Cc: hgoffin at amazon.com

Hi Greg,

Is there any chance this can get applied?  It fixes a regression on
5.15 and 5.16.

Thanks,

Alex

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
> index cd0acbea75da..d58ab9deb028 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
> @@ -341,7 +341,8 @@ int amdgpu_fbdev_init(struct amdgpu_device *adev)
>         }
>
>         /* disable all the possible outputs/crtcs before entering KMS mode */
> -       if (!amdgpu_device_has_dc_support(adev) && !amdgpu_virtual_display)
> +       if (!amdgpu_device_has_dc_support(adev) && !amdgpu_virtual_display &&
> +           !amdgpu_sriov_vf(adev))
>                 drm_helper_disable_unused_functions(adev_to_drm(adev));
>
>         drm_fb_helper_initial_config(&rfbdev->helper, bpp_sel);
> --
> 2.35.3
>