[Nouveau] [PATCH v2] drm: don't continue with anything after the GPU couldn't be woken up

[Thierry Reding]

On Tue, Nov 21, 2017 at 04:01:16PM +0100, Karol Herbst wrote:
> This should make systems more stable where resuming the GPU fails. This
> can happen due to bad firmware or due to a bug within the kernel. The
> last thing which should happen in either case is an unusable system.
> 
> v2: do the same in nouveau_pmops_resume
> 
> Tested-by: Karl Hastings <kazen at redhat.com>
> Signed-off-by: Karol Herbst <kherbst at redhat.com>
> ---
>  drm/nouveau/nouveau_drm.c | 31 +++++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/drm/nouveau/nouveau_drm.c b/drm/nouveau/nouveau_drm.c
> index 8d4a5be3..6e4cb4f7 100644
> --- a/drm/nouveau/nouveau_drm.c
> +++ b/drm/nouveau/nouveau_drm.c
> @@ -792,6 +792,27 @@ nouveau_pmops_suspend(struct device *dev)
>  	return 0;
>  }
>  
> +static int
> +nouveau_set_power_state_D0(struct pci_dev *pdev)
> +{
> +	struct nouveau_drm *drm = nouveau_drm(pci_get_drvdata(pdev));
> +	int ret;
> +
> +	pci_set_power_state(pdev, PCI_D0);
> +	/* abort if anything went wrong */
> +	if (pdev->current_state != PCI_D0) {
> +		NV_ERROR(drm, "couldn't wake up GPU!\n");
> +		return -EBUSY;
> +	}

Looks to me like the more idiomatic way to do this is:

	ret = pci_set_power_state(pdev, PCI_D0);
	if (ret < 0 && ret != -EIO)
		return ret;

> +	pci_restore_state(pdev);
> +	ret = pci_enable_device(pdev);
> +	if (ret)
> +		return ret;
> +
> +	pci_set_master(pdev);

Looking closer it also seems like pci_enable_device() will already set
the power state to D0 (via do_pci_enable_device()). Is the sequence
above really necessary because the hardware is quirky, or was it
cargo-culted?

Thierry
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