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

[Karol Herbst]

On Tue, Nov 21, 2017 at 6:46 PM, Thierry Reding
<thierry.reding at gmail.com> wrote:
> 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;
>

I thought so too, but it ends up returning 0 even if setting the power
state fails. Or maybe I did something wrong when installing the
kernel. I could take another shot at it, but what I came up with seems
to work. Adding airlied in CC, because he saw my patch and didn't
complain about it. Hopefully he knows more.

>> +     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

No clue. And because it was already there in the original code I
didn't really felt like doing anything with it.